Only one-third of people who could benefit from the medication, known as preexposure prophylaxis or PrEP, are prescribed it, according to the Centers for Disease Control and Prevention.

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Among infectious-disease doctors like me, Banu is famous as a symbol of the power of science and modern medicine.

And yet, beyond that distinction, Banu has largely been forgotten by the public. That fate is a reminder that, well after a global pandemic recedes from headlines in wealthy countries, its survivors have needs that go unmet. Although Banu survived smallpox, she’s been sickly her whole life. She was once bedridden for three months with fevers and vomiting, but she couldn’t afford to see a good doctor. The doctor she could afford, she recalled, prescribed her cooked fish heads. Banu also complains of poor vision: “I cannot thread a needle, because I cannot see clearly,” she told me, via a translator, during an interview in Digholdi, the village where she lives.

“I cannot examine the lice on my son’s head and cannot read the Quran well because of my vision,” she said.

In the years following smallpox eradication, journalists from all over the world traveled to interview Banu, but they petered out years ago. “Mother is so famous, but they do not take any follow-up of Mom to know whether she is in a good or bad state,” her middle daughter, Nazma Begum, told me.

Banu and her family are proud of her place in history, but their role in the eradication of smallpox speaks to the limits of merely fighting diseases. In his biography of the doctor and philanthropist Paul Farmer, author Tracy Kidder recorded a Haitian saying: “Giving people medicine for TB and not giving them food is like washing your hands and drying them in the dirt.”

After Banu and her family survived smallpox, the rest of the world dried its hands in the dirt — just as it did for the poorest victims of covid-19 and later the most marginalized people with mpox, formerly known as monkeypox.

I traveled to South Asia to speak with aging public health workers and smallpox survivors in South Asia for the audio-documentary podcast “Epidemic: Eradicating Smallpox.”

To meet Banu, I flew 14 hours to Delhi and another two hours the next day to Dhaka, then took a five-hour drive to Barishal, followed the next day by a 90-minute ferry ride and a two-hour drive to arrive in Digholdi. Banu and her family — her husband, their three daughters, and their son — share a one-room bamboo-and-corrugated-metal home with a mud floor. The home, which lacks indoor plumbing, is divided down the middle by a screen and a curtain. Water leaks in through the roof, soaking their beds. A bare bulb hangs from a wire overhead. Her in-laws used to live with them, too, but they have passed away.

Women in rural Bangladesh rarely work outside the home. Banu’s husband, Rafiqul Islam, pedals a rickshaw. Some days he earns nothing. On a good day, he might make 500 taka (not quite $5). Although the World Health Organization arranged for a plot of land in her name, Banu said, the family has nowhere to cultivate. “They gave me the land, but the river consumes that. Some of it is in the river,” she said. Cyclones and rising sea levels have led to coastal erosion and saltwater intrusion, and there have also been land disputes.

Begum, now 23, completed a year of college but then dropped out. Banu and her husband couldn’t afford the fees. Instead, they arranged for her to marry. Her mother’s fame “did not help me in any way in my studies or financially,” Begum told me.

The family’s financial life is precarious. Five hundred taka used to buy a 10-kilogram bag of rice and vegetables. During my visit in 2022, the instability of the Russia-Ukraine war created fluctuating oil prices, and Banu said that amount was enough to pay only for the rice.

Banu is well aware that thanks to vaccination, millions of people no longer die of smallpox and other infectious diseases. By one estimate, the eradication of smallpox has prevented at least 5 million deaths around the world each year. Vaccines remain one of the most cost-effective and lifesaving gifts of modern medicine. The Centers for Disease Control and Prevention estimates that the U.S. saves 10 times what it spends on childhood vaccination. But all this is cold comfort to Banu when she and her family are struggling to survive.

Every public health crisis leaves people behind. When I worked as an Ebola aid worker in Guinea in 2015, residents asked why I cared so much about Ebola when local women were hemorrhaging in childbirth and didn’t have enough to eat. They were right not to trust our efforts. Why should they upend their lives to help us defeat Ebola? They knew their lives wouldn’t be materially better when we declared victory and left, as we had done so many times before as soon as our own interests were protected. Their prediction was correct.

As the coronavirus pandemic winds down in the United States, Banu’s life is a reminder that illness has a long tail of consequences and doesn’t end with a single shot. The world’s most powerful nation hasn’t ensured equitable access for its own citizens to health care and lifesaving tools such as covid vaccines, Paxlovid, and monoclonal antibodies. The resulting disparities will get worse as the federal government finishes turning America’s emergency covid response over to the routine health care system. Many Americans can’t afford to stay home when they or their children are sick. Families lack support to care for young or elder family members or people with medical illnesses or disabilities. Many say their biggest worry is paying for groceries or gas to get to work.

Their plight is less extreme than Banu’s, but their suffering is real — and it is magnified worldwide. As long as vulnerable communities are deprived of holistic, comprehensive responses to mpox, covid, Ebola, or other public health emergencies to come, these people will have a reason to be suspicious, and enlisting their help to fight the next crisis will be that much harder.

A version of this article first appeared in The Atlantic in August 2022.

KFF Health News is a national newsroom that produces in-depth journalism about health issues and is one of the core operating programs at KFF—an independent source of health policy research, polling, and journalism. Learn more about KFF.

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Last year, the emergence of the highly transmissible omicron variant of the covid-19 virus caught many people by surprise and led to a surge in cases that overwhelmed hospitals and drove up fatalities. Now we’re learning that omicron is mutating to better evade the immune system.

Omicron-specific vaccines were authorized by the FDA in August and are recommended by U.S. health officials for anyone 5 or older. Yet only half of adults in the United States have heard much about these booster shots, according to a recent KFF poll, and only a third say they’ve gotten one or plan to get one as soon as possible. In 2020 and 2021, covid cases spiked in the U.S. between November and February.

Although we don’t know for sure that we’ll see another surge this winter, here’s what you should know about covid and the updated boosters to prepare.

1. Do I need a covid booster shot this fall?

If you’ve completed a primary vaccination series and are 50 or older, or if your immune system is compromised, get a covid booster shot as soon as possible. Forty percent of deaths are occurring among people 85 and older and almost 90% among people 65 and over. Although people of all ages are being hospitalized from covid, those hospitalizations are also skewing older.

Unvaccinated people, while in the minority in the U.S., are still at the highest risk of dying from covid. It’s not too late to get vaccinated ahead of this winter season. The United Kingdom, whose covid waves have presaged those in the United States by about a month, is beginning to see another increase in cases.

If you’ve already received three or more covid shots, you’re 12 to 49 years old, and you’re not immunocompromised, your risk of hospitalization and death from the disease is significantly reduced and additional boosters are not likely to add much protection.

However, getting a booster shot provides a “honeymoon” period for a couple of months after vaccination, during which you’re less likely to get infected and thus less likely to transmit the virus to others. If you’ll be seeing older, immunocompromised, or otherwise vulnerable family and friends over the winter holidays, you might want to get a booster two to four weeks in advance to better shield them against covid.

You may have other reasons for wanting to avoid infection, like not wanting to have to stay home from work because you or your child is sick with covid. Even if you aren’t hospitalized from covid, it can be costly to lose wages or arrange for backup child care.

One major caveat to these recommendations: You should wait four to six months after your last covid infection or vaccination before getting another shot. A dose administered too soon will be less effective because antibodies from the previous infection or vaccination will still be circulating in your blood and will prevent your immune cells from seeing and responding to vaccination.

2. Do kids need to be vaccinated even if they’ve had covid?

Although children are at lower risk for severe covid than are adults, the stakes for kids are higher than many diseases already recognized as dangerous. Their risk shouldn’t be measured against the risk that covid poses to other age groups but against the risk they face from other preventable diseases. In the first two years of the pandemic, covid was the fourth- or fifth-leading cause of death in every five-year age bracket from birth to 19, killing almost 1,500 children and teenagers. Other vaccine-preventable diseases like chickenpox, rubella, and rotavirus killed an average of about 20-50 children and teens a year before vaccines became available. By that measure, vaccinating kids against covid is a slam-dunk.

Children who have had covid also benefit from vaccination. The vaccine reduces their risk of hospitalization and missing days of school, when parents might need to stay home with them.

But it’s precisely because the stakes are higher for kids that many parents are anxious about getting their children vaccinated. As recently as July, just after the FDA authorized covid vaccines for children as young as 6 months, a KFF poll found that over half of parents of children under age 5 said they thought vaccines posed a greater risk to the health of their child than getting the disease. And in the most recent poll, half said they had no plans to get their children vaccinated. Covid vaccination rates range from 61% among children ages 12 to 17 to 2% among kids younger than 2.

Similar to influenza, covid is most deadly for the very youngest and oldest. At especially high risk are infants. They’re unlikely to have immunity from infection, and a small share have been vaccinated. Unless their mothers were vaccinated during pregnancy or got covid during pregnancy — the latter of which poses a high risk of death for the mother and of preterm birth for the baby — infants are probably not getting protective antibodies against covid through breast milk. And because infants have small airways and weaker coughs, they’re more likely to have trouble breathing with any respiratory infection, even one less deadly than covid.

3. Will I need a covid shot every year?

It depends on the targets set by public health officials whether covid becomes a seasonal virus like the flu, and how much the virus continues to mutate and evade humanity’s immune defenses.

If the goal of vaccination is to prevent severe disease, hospitalization, and death, then many people will be well protected after their primary vaccination series and may not need additional shots. Public health officials might strongly recommend boosters for older and immunocompromised people while leaving the choice of whether to get boosted to those with lower risk. If the goal of vaccination is to prevent infection and transmission, then repeat boosters will be needed after completing the primary vaccination series and as often as a couple of times a year.

Influenza is a seasonal virus causing infections and disease generally in the winter, but scientists don’t know whether covid will settle into a similar, predictable pattern. In the first three years of the pandemic, the United States has experienced waves of infection in summer. But if the covid virus were to become a wintertime virus, public health officials might recommend yearly boosters. The Centers for Disease Control and Prevention recommends that people 6 months and older get a flu shot every year with very rare exceptions. However, as with the flu, public health officials might still place a special emphasis on vaccinating high-risk people against covid.

And the more the virus mutates, the more often public health officials may recommend boosting to overcome a new variant’s immune evasion. Unfortunately, this year’s updated omicron booster doesn’t appear to provide significantly better protection than the original boosters. Scientists are working on variant-proof vaccines that could retain their potency in the face of new variants.

4. Are more covid variants on the way?

The omicron variant has burst into an alphabet soup of subvariants. The BA.5 variant that surfaced earlier this year remains the dominant variant in the U.S., but the BA.4.6 omicron subvariant may be poised to become dominant in the United States. It now accounts for 14% of cases and is rising. The BA.4.6 omicron subvariant is better than BA.5 at dodging people’s immune defenses from both prior infection and vaccination.

In other parts of the world, BA.4.6 has been overtaken by BA.2.75 and BF.7 (a descendant of BA.5), which respectively account for fewer than 2% and 5% of covid cases in the U.S. The BA.2.75.2 omicron subvariant drove a wave of infections in South Asia in July and August. Although the U.S. hasn’t yet seen much in the way of another variant descended from BA.5 — BQ.1.1 — it is rising quickly in other countries like the U.K., Belgium, and Denmark. The BA.2.75.2 and BQ.1.1 variants may be the most immune-evasive omicron subvariants to date.

BA.4.6, BA.2.75.2, and BQ.1.1 all evade Evusheld, the monoclonal antibody used to prevent covid in immunocompromised people who don’t respond as well to vaccination. Although another medication, bebtelovimab, remains active in treating covid from BA.4.6 and BA.2.75.2, it’s ineffective against BQ.1.1. Many scientists are worried that Evusheld will become useless by November or December. This is concerning because the pipeline for new antiviral pills and monoclonal antibodies to treat covid is running dry without a guaranteed purchaser to ensure a market. In the past, the federal government guaranteed it would buy vaccines in bulk, but funding for that program has not been extended by Congress.

Other omicron subvariants on the horizon include BJ.1, BA.2.3.20, BN.1, and XBB, all descendants of BA.2.

It’s hard to predict whether an omicron subvariant or yet another variant will come to dominate this winter and whether hospitalizations and deaths will again surge in the U.S. Vaccination rates and experience with prior infections vary around the world and even within the United States, which means that the different versions of omicron are duking it out on different playing fields.

While this might all sound grim, it’s important to remember that covid booster shots can help overcome immune evasion by the predominant omicron subvariants.

5. What about long covid?

Getting vaccinated does reduce the risk of getting long covid, but it’s unclear by how much. Researchers don’t know if the only way to prevent long covid is to prevent infection.

Although vaccines may curb the risk of infection, few vaccines prevent all or almost all infections. Additional measures — such as improving indoor air quality and donning masks — would be needed to reduce the risk of infection. It’s also not yet known whether prompt treatment with currently available monoclonal antibodies and antiviral drugs like Paxlovid reduces the risk of developing long covid.

6. Do I need a flu shot, too?

The CDC recommends that anyone 6 months of age or older get an annual flu shot. The ideal timing is late October or early November, before the winter holidays and before influenza typically starts spreading in the U.S. Like covid shots, flu shots provide only a couple of months of immunity against infection and transmission, but an early flu shot is better than no flu shot. Influenza is already circulating in some parts of the United States.

It’s especially important for people 65 or older, pregnant women, people with chronic medical conditions, and children under 5 to get their yearly flu shots because they’re at highest risk of hospitalization and death. Although younger people might be at lower risk for severe flu, they can act as vectors for transmission of influenza to higher-risk people in the community.

High-dose flu vaccines and “adjuvanted” flu vaccines are recommended for people 65 and older. Adjuvants strengthen the immune response to a vaccine.

It is safe to get vaccinated for covid and the flu at the same time, but you might experience more side effects like fevers, headache, or body aches.

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Ahora que la poliomielitis vuelve a aparecer décadas después de que se considerara eliminada en Estados Unidos, los que no están familiarizados con la temida enfermedad necesitan una guía para protegerse a sí mismos y a sus hijos, muchos de los cuales están saliendo del trauma de la pandemia de covid-19.

¿Qué es la poliomielitis?

Polio es la abreviatura de “poliomielitis”, una enfermedad neurológica causada por una infección por poliovirus. De los tres tipos de poliovirus salvajes —serotipos 1, 2 y 3—, el serotipo 1 es el más virulento y el que tiene más probabilidades de causar parálisis.

La mayoría de las personas infectadas por el poliovirus no enferman ni presentan síntomas. Alrededor de una cuarta parte de los infectados pueden experimentar síntomas leves como fatiga, fiebre, dolor de cabeza, rigidez de cuello, dolor de garganta, náuseas, vómitos y dolor abdominal. Por tanto, al igual que con el covid-19, las personas que no presentan síntomas pueden contagiar sin saberlo al interactuar con otras personas.

Pero en hasta una de cada 200 personas con esta infección, el virus puede atacar la médula espinal y el cerebro. Cuando infecta la médula espinal, las personas pueden desarrollar debilidad muscular o parálisis, incluso de las piernas, el brazo o la pared torácica. El poliovirus también puede infectar el cerebro, provocando dificultades para respirar o tragar.

Las personas pueden desarrollar el síndrome post-polio décadas después de la infección. Los síntomas pueden incluir dolor muscular y debilidad.

Las personas con poliomielitis pueden permanecer en silla de ruedas o ser incapaces de respirar sin la ayuda de un respirador por el resto de sus vidas.

¿Cómo se propaga la poliomielitis?

El virus que causa la poliomielitis se propaga por la “vía oral-fecal”, lo que significa que entra en el cuerpo a través de la boca por medio de las manos, el agua, los alimentos u otros artículos contaminados con heces que contienen el poliovirus. En raras ocasiones, el poliovirus puede propagarse a través de la saliva y las gotitas de las vías respiratorias superiores. El virus infecta entonces la garganta y el tracto gastrointestinal, se extiende a la sangre e invade el sistema nervioso.

¿Cómo se diagnostica la poliomielitis?

La poliomielitis se diagnostica mediante una combinación de charlas con el paciente, exámenes físicos, pruebas de laboratorio y exploraciones de la médula espinal o el cerebro. Los proveedores de salud pueden enviar heces, frotis de garganta, líquido cefalorraquídeo y otras muestras para su análisis en el laboratorio. Pero como la poliomielitis ha sido cada vez menos frecuente en Estados Unidos durante décadas, los médicos pueden no considerar el diagnóstico en pacientes con síntomas. Y las pruebas para la sospecha de poliomielitis deben enviarse a los Centros para el Control y la Prevención de Enfermedades (CDC), ya que incluso los centros académicos ya no realizan las pruebas.

¿Cómo se puede prevenir la transmisión del poliovirus?

Los CDC recomiendan que se vacune a todos los niños contra la poliomielitis a las edades de 2, 4, 6 a 18 meses y 4 a 6 años, para un total de cuatro dosis. Los 50 estados y el Distrito de Columbia exigen que los niños que van a la guardería o a la escuela pública sean vacunados contra la polio, pero algunos estados permiten exenciones médicas, religiosas o personales.

El programa Vaccines for Children proporciona la vacuna contra la polio de forma gratuita a los niños que tienen Medicaid, que no tienen seguro o que tienen un seguro insuficiente, o que son miembros de comunidades indígenas americanas o nativos de Alaska.

La mayoría de las personas nacidas en Estados Unidos después de 1955 probablemente hayan recibido la vacuna contra la polio. Pero en algunas zonas las tasas de vacunación son peligrosamente bajas, como en el condado neoyorquino de Rockland, donde es del 60%, y en el condado de Yates, donde es del 54%, debido a que muchas familias alegan exenciones religiosas.

Hay dos tipos de vacunas contra la polio: la vacuna antipoliomielítica inactivada (IPV) y la vacuna antipoliomielítica oral debilitada (OPV). La IPV es una vacuna inyectable. La OPV puede administrarse en gotas o en un terrón de azúcar, por lo que es más fácil de administrar. Ambas vacunas son muy eficaces contra la poliomielitis paralítica, pero la OPV parece ser más eficaz para prevenir la infección y la transmisión.

Tanto el poliovirus salvaje como los virus vivos y debilitados de la OPV pueden causar la infección. Dado que la VPI es una vacuna de virus muertos, no puede infectar ni replicarse, ni dar lugar a poliovirus derivados de la vacuna, y tampoco causar la enfermedad de la poliomielitis paralítica. Los virus debilitados de la OPV pueden mutar y recuperar su capacidad de causar parálisis, lo que se denomina poliomielitis derivada de la vacuna.

Desde el año 2000, en Estados Unidos sólo se administra la IPV. Dos dosis de IPV tienen una eficacia de al menos el 90% y tres dosis de IPV tienen una eficacia de al menos el 99% en la prevención de la enfermedad de la poliomielitis paralítica. Estados Unidos dejó de utilizar la OPV debido al riesgo de parálisis de 1 en 2,000 entre las personas no vacunadas que la recibían. Algunos países siguen utilizando la OPV.

En Estados Unidos, la vacunación contra la poliomielitis comenzó en 1955. Los casos de poliomielitis paralítica se redujeron de más de 15,000 al año a principios de esa década a menos de 100 en la década de 1960, y luego a menos de 10 en la década de 1970. En la actualidad, el poliovirus tiene más probabilidades de propagarse en los lugares donde la higiene y el saneamiento son deficientes, y las tasas de vacunación son bajas.

¿Por qué la polio se está extendiendo de nuevo?

La Organización Mundial de la Salud (OMS) declaró a Norteamérica y Sudamérica libre de poliomielitis a partir de 1994, pero en junio de 2022, a un joven adulto que vivía en el condado de Rockland, Nueva York, se le diagnosticó el poliovirus del serotipo 2 derivado de la vacuna.

El paciente se quejó de fiebre, rigidez en el cuello y debilidad en las piernas. No había viajado recientemente fuera del país por lo que se supuso que se había infectado en Estados Unidos. Desde entonces, los CDC han empezado a vigilar las aguas residuales para detectar el poliovirus.

El poliovirus vinculado genéticamente al caso del condado de Rockland se ha detectado en muestras de aguas residuales de los condados de Rockland, Orange y Sullivan, lo que demuestra la propagación en la comunidad desde mayo de 2022. También se han detectado poliovirus no relacionados con la vacuna en las aguas residuales de la ciudad de Nueva York.

¿Cómo puedo saber si he sido vacunado contra la poliomielitis?

No existe una base de datos nacional de registros de vacunación, pero los 50 estados y el Distrito de Columbia tienen sistemas de información sobre vacunación con registros que se remontan a la década de 1990. Tu departamento de salud estatal o territorial también puede tener registros de tus vacunas.

Las personas vacunadas en Arizona, el Distrito de Columbia, Louisiana, Maryland, Mississippi, Dakota del Norte y Washington pueden acceder a sus registros de vacunación mediante la aplicación MyIR Mobile, y quienes se vacunaron en Idaho, Minnesota, Nueva Jersey y Utah pueden hacerlo mediante la aplicación Docket.

También puedes preguntar a tus padres, al pediatra, a tu médico o farmacéutico, o a las escuelas de K-12, colegios o universidades a las que fuiste si tienen registros de tus vacunas. Algunos empleadores, como los sistemas de salud, también pueden guardar registros de tus vacunas en su oficina de salud ocupacional.

No hay ninguna prueba para determinar si eres inmune a la polio.

¿Necesito un refuerzo de la vacuna antipoliomielítica si fui vacunado completamente contra la poliomielitis cuando era niño?

Todos los niños y adultos no vacunados deben completar la serie de cuatro dosis de vacunas contra la polio recomendada por los CDC. No necesitas un refuerzo de la IPV si recibiste la OPV.

Los adultos que estén inmunodeprimidos, que viajen a un país en el que circule el poliovirus o que estén en mayor riesgo de exposición al poliovirus en el trabajo, como algunos trabajadores de laboratorio y sanitarios, pueden recibir un refuerzo de la IPV una sola vez.

¿Cómo se trata la polio?

Las personas con una infección leve por poliovirus no necesitan tratamiento. Los síntomas suelen desaparecer por sí solos en un par de días.

La poliomielitis paralítica no tiene cura. El tratamiento se centra en la fisioterapia y la terapia ocupacional para ayudar a los pacientes a adaptarse y recuperar la funcionalidad.

¿Por qué no se ha erradicado el poliovirus?

La viruela es el único virus humano que se ha declarado erradicado hasta la fecha. Una enfermedad puede ser erradicada si solo infecta a los seres humanos, si la infección viral induce una inmunidad a largo plazo contra la reinfección y si existe una vacuna eficaz u otro tipo de prevención. Cuanto más infeccioso sea un virus, más difícil será su erradicación. Los virus que se propagan sin presentar síntomas también son más difíciles de erradicar.

En 1988, la Asamblea Mundial de la Salud se propuso erradicar la poliomielitis para el año 2000. Los conflictos violentos, la propagación de teorías conspirativas, el escepticismo sobre las vacunas, la financiación y la voluntad política inadecuadas, y los esfuerzos de vacunación de baja calidad ralentizaron el progreso hacia la erradicación, pero antes de la pandemia de coronavirus, el mundo había estado muy cerca de erradicar la poliomielitis.

Durante la pandemia, la vacunación infantil, incluida la de la poliomielitis, disminuyó en Estados Unidos y en todo el mundo.

Para erradicar la poliomielitis, el mundo debe eliminar todos los poliovirus salvajes y los poliovirus derivados de las vacunas. Los serotipos 2 y 3 del poliovirus salvaje han sido erradicados. El serotipo 1 del poliovirus salvaje, la forma más virulenta, sigue siendo endémico solo en Pakistán y Afganistán, pero los poliovirus derivados de la vacuna siguen circulando en algunos países de África y otras partes del mundo.

Para erradicar definitivamente la poliomielitis del planeta, es probable que se necesite un enfoque por etapas que incluya el uso de la OPV, luego una combinación de OPV y IPV, y después, la IPV sola.

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What is poliomyelitis?

Polio is short for “poliomyelitis,” a neurological disease caused by a poliovirus infection. Of the three types of wild poliovirus — serotypes 1, 2, and 3 — serotype 1 is the most virulent and the most likely to cause paralysis.

Most people infected with poliovirus don’t get sick and won’t have symptoms. About a quarter of those infected might experience mild symptoms like fatigue, fever, headache, neck stiffness, sore throat, nausea, vomiting, and abdominal pain. So, as with covid-19, people who don’t have symptoms can unknowingly spread it as they interact with others. But in up to 1 in 200 people with a poliovirus infection, the virus may attack the spinal cord and brain. When it infects the spinal cord, people may develop muscle weakness or paralysis, including of the legs, arm, or chest wall. Poliovirus may also infect the brain, leading to difficulty breathing or swallowing.

People can develop post-polio syndrome decades after infection. Symptoms may include muscle pain, weakness, and wasting.

People with poliomyelitis may remain wheelchair-bound or unable to breathe without the help of a ventilator for the rest of their lives.

How does polio spread?

The virus that causes polio spreads through the “oral-fecal route,” which means it enters the body through the mouth by way of the hands, water, food, or other items contaminated with poliovirus-containing feces. Rarely, poliovirus may spread through saliva and upper respiratory droplets. The virus then infects the throat and gastrointestinal tract, spreads to the blood, and invades the nervous system.

How do doctors diagnose polio?

Poliomyelitis is diagnosed through a combination of patient interviews, physical examinations, lab testing, and scans of the spinal cord or brain. Health care providers may send feces, throat swabs, spinal fluid, and other specimens for lab testing. But because polio has been vanishingly rare in the United States for decades, doctors may not consider the diagnosis for patients with symptoms. And tests for suspected polio must be sent to the Centers for Disease Control and Prevention, since even academic centers no longer perform the tests.

How can poliovirus transmission be prevented?

The CDC recommends that all children be vaccinated against polio at ages 2 months, 4 months, 6 to 18 months, and 4 to 6 years, for a total of four doses. All 50 states and the District of Columbia require that children attending day care or public school be immunized against polio, but some states allow medical, religious, or personal exemptions. The Vaccines for Children program provides polio vaccine free of charge for children who are eligible for Medicaid, uninsured, or underinsured, or who are American Indian or Alaska Native. Most people born in the United States after 1955 likely have been vaccinated for polio. But in some areas the vaccination rates are dangerously low, such as New York’s Rockland County, where it is 60%, and Yates County, where it is 54%, because so many families there claim religious exemptions.

There are two types of polio vaccine: killed, inactivated polio vaccine (IPV) and weakened, live, oral polio vaccine (OPV). IPV is an injectable vaccine. OPV may be given by drops in the mouth or on a sugar cube, so it’s easier to administer. Both vaccines are highly effective against paralytic poliomyelitis, but OPV appears to be more effective in preventing infection and transmission.

Both the wild poliovirus and the live, weakened OPV viruses can cause infection. Because IPV is a killed virus vaccine, it cannot infect or replicate, give rise to vaccine-derived poliovirus, or cause paralytic poliomyelitis disease. The weakened, OPV viruses can mutate and regain their ability to cause paralysis — what’s called vaccine-derived poliomyelitis.

Since 2000, only IPV has been given in the United States. Two doses of IPV are at least 90% effective and three doses of IPV are at least 99% effective in preventing paralytic poliomyelitis disease. The United States stopped using OPV due to a 1-in-2,000 risk of paralysis among unvaccinated persons receiving OPV. Some countries still use OPV.

Vaccination against polio began in 1955 in the United States. Cases of paralytic poliomyelitis disease plummeted from over 15,000 a year in the early 1950s to under 100 in the 1960s and then down to fewer than 10 in the 1970s. Today, poliovirus is most likely to spread where hygiene and sanitation are poor and vaccination rates are low.

Why is polio spreading again?

The World Health Organization declared North and South America polio-free as of 1994, but in June 2022, a young adult living in Rockland County, New York, was diagnosed with serotype 2 vaccine-derived poliovirus. The patient complained of fever, neck stiffness, and leg weakness. The patient had not traveled recently outside the country and was presumably infected in the United States. The CDC has since started to monitor wastewater for poliovirus. Poliovirus genetically linked to the Rockland County case has been detected in wastewater samples from Rockland, Orange, and Sullivan counties, demonstrating community spread as far back as May 2022. Unrelated vaccine-derived poliovirus has also been detected in New York City wastewater.

How do I know if I’ve been vaccinated against polio?

There is no national database of immunization records, but all 50 states and the District of Columbia have immunization information systems with records going as far back as the 1990s. Your state or territorial health department may also have records of your vaccinations. People immunized in Arizona, the District of Columbia, Louisiana, Maryland, Mississippi, North Dakota, and Washington can access their immunization records using the MyIR Mobile app, and those who got vaccines in Idaho, Minnesota, New Jersey, and Utah can do so using the Docket app.

You may also ask your parents, your childhood pediatrician, your current doctor or pharmacist, or the K-12 schools, colleges, or universities you attended if they have records of your vaccinations. Some employers, like health care systems, may also keep records of your vaccinations in their occupational health office.

There is no test to determine if you’re immune to polio.

Do I need a polio vaccine booster if I was fully vaccinated against polio as a child?

All children and unvaccinated adults should complete the CDC-recommended four-dose series of polio vaccinations. You do not need an IPV booster if you received OPV.

Adults who are immunocompromised, traveling to a country where poliovirus is circulating, or at increased risk for exposure to poliovirus on the job, such as some lab workers and health care workers, may get a one-time IPV booster.

How is polio treated?

People with mild poliovirus infection don’t require treatment. Symptoms usually go away on their own within a couple of days.

There is no cure for paralytic poliomyelitis. Treatment focuses on physical and occupational therapy to help patients adapt and regain function.

Why hasn’t poliovirus been eradicated?

Smallpox is the only human virus to have been declared eradicated to date. A disease may be eradicated if it infects only humans, if viral infection induces long-term immunity to reinfection, and if an effective vaccine or other preventive exists. The more infectious a virus, the more difficult it is to eradicate. Viruses that spread asymptomatically are also more difficult to eradicate.

In 1988, the World Health Assembly resolved to eradicate polio by 2000. Violent conflict, the spread of conspiracy theories, vaccine skepticism, inadequate funding and political will, and poor-quality vaccination efforts slowed progress toward eradication, but before the covid pandemic, the world had gotten very close to eradicating polio. During the pandemic, childhood immunizations, including polio vaccinations, dipped in the U.S. and around the world.

To eradicate polio, the world must eradicate all wild polioviruses and vaccine-derived polioviruses. Wild poliovirus serotypes 2 and 3 have been eradicated. Wild poliovirus serotype 1, the most virulent form, remains endemic only in Pakistan and Afghanistan, but vaccine-derived polioviruses continue to circulate in some countries in Africa and other parts of the world. A staged approach involving the use of OPV, then a combination of OPV and IPV, and then IPV alone would likely be needed to finally eradicate polio from the planet.

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But for those familiar with the business tactics of the pharmaceutical industry, that exuberant messaging — combined with the lack of completed studies — has caused considerable heartburn and raised an array of unanswered concerns.

The updated shots easily clear the “safe and effective” bar for government authorization. But in the real world, are the omicron-specific vaccines significantly more protective — and in what ways — than the original covid vaccines so many have already taken? If so, who would benefit most from the new shots? Since the federal government is purchasing these new vaccines — and many of the original, already purchased vaccines may never find their way into taxpayers’ arms — is the $3.2 billion price tag worth the unclear benefit? Especially when these funds had to be pulled from other covid response efforts, like testing and treatment.

Several members of the CDC advisory committee that voted 13-1 for the recommendation voiced similar questions and concerns, one saying she only “reluctantly” voted in the affirmative.

Some said they set aside their desire for more information and better data and voted yes out of fear of a potential winter covid surge. They expressed hope that the new vaccines — or at least the vaccination campaign that would accompany their rollout — would put a dent in the number of future cases, hospitalizations, and deaths.

That calculus is, perhaps, understandable at a time when an average of more than 300 Americans are dying of covid each day.

But it leaves front-line health care providers in the impossible position of trying to advise individual patients whether and when to take the hot, new vaccines without complete data and in the face of marketing hype.

Don’t get us wrong. We’re grateful and amazed that Pfizer-BioNTech and Moderna (with assists from the National Institutes of Health and Operation Warp Speed) developed an effective vaccine in record time, freeing the nation from the deadliest phase of the covid pandemic, when thousands were dying each day. The pandemic isn’t over, but the vaccines are largely credited for enabling most of America to return to a semblance of normalcy. We’re both up-to-date with our covid vaccinations and don’t understand why anyone would choose not to be, playing Russian roulette with their health.

But as society moves into the next phase of the pandemic, the pharmaceutical industry may be moving into more familiar territory: developing products that may be a smidgen better than what came before, selling — sometimes overselling — their increased effectiveness in the absence of adequate controlled studies or published data, advertising them as desirable for all when only some stand to benefit significantly, and in all likelihood raising the price later.

This last point is concerning because the government no longer has funds to purchase covid vaccines after this autumn. Funding to cover the provider fees for vaccinations and community outreach to those who would most benefit from vaccination has already run out. So updated boosters now and in the future will likely go to the “worried well” who have good insurance rather than to those at highest risk for infection and progression to severe disease.

The FDA’s mandated task is merely to determine whether a new drug is safe and effective. However, the FDA could have requested more clinical vaccine effectiveness data from Pfizer and Moderna before authorizing their updated omicron BA.5 boosters.

Yet the FDA cannot weigh in on important follow-up questions: How much more effective are the updated boosters than vaccines already on the market? In which populations? And what increase in effectiveness is enough to merit an increase in price (a so-called cost-benefit analysis)? Other countries, such as the United Kingdom, perform such an analysis before allowing new medicines onto the market, to negotiate a fair national price.

The updated booster vaccine formulations are identical to the original covid vaccines except for a tweak in the mRNA code to match the omicron BA.5 virus. Studies by Pfizer showed that its updated omicron BA.1 booster provides a 1.56 times higher increase in neutralizing antibody titers against the BA.1 virus as compared with a booster using its original vaccine. Moderna’s studies of its updated omicron BA.1 booster demonstrated very similar results. However, others predict that a 1.5 times higher antibody titer would yield only slight improvement in vaccine effectiveness against symptomatic illness and severe disease, with a bump of about 5% and 1% respectively. Pfizer and Moderna are just starting to study their updated omicron BA.5 boosters in human trials.

Though the studies of the updated omicron BA.5 boosters were conducted only in mice, the agency’s authorization is in line with precedent: The FDA clears updated flu shots for new strains each year without demanding human testing. But with flu vaccines, scientists have decades of experience and a better understanding of how increases in neutralizing antibody titers correlate with improvements in vaccine effectiveness. That’s not the case with covid vaccines. And if mouse data were a good predictor of clinical effectiveness, we’d have an HIV vaccine by now.

As population immunity builds up through vaccination and infection, it’s unclear whether additional vaccine boosters, updated or not, would benefit all ages equally. In 2022, the U.S. has seen covid hospitalization rates among people 65 and older increase relative to younger age groups. And while covid vaccine boosters seem to be cost-effective in the elderly, they may not be in younger populations. The CDC’s Advisory Committee on Immunization Practices considered limiting the updated boosters to people 50 and up, but eventually decided that doing so would be too complicated.

Unfortunately, history shows that — as with other pharmaceutical products — once a vaccine arrives and is accompanied by marketing, salesmanship trumps science: Many people with money and insurance will demand it whether data ultimately proves it is necessary for them individually or not.

We are all likely to encounter the SARS-CoV-2 virus again and again, and the virus will continue to mutate, giving rise to new variants year after year. In a country where significant portions of at-risk populations remain unvaccinated and unboosted, the fear of a winter surge is legitimate.

But will the widespread adoption of a vaccine — in this case yearly updated covid boosters — end up enhancing protection for those who really need it or just enhance drugmakers’ profits? And will it be money well spent?

The federal government has been paying a negotiated price of $15 to $19.50 a dose of mRNA vaccine under a purchasing agreement signed during the height of the pandemic. When those government agreements lapse, analysts expect the price to triple or quadruple, and perhaps even more for updated yearly covid boosters, which Moderna’s CEO said would evolve “like an iPhone.” To deploy these shots and these dollars wisely, a lot less hype and a lot more information might help.

KFF Health News is a national newsroom that produces in-depth journalism about health issues and is one of the core operating programs at KFF—an independent source of health policy research, polling, and journalism. Learn more about KFF.

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This story can be republished for free (details).