The United States is officially added to the WHO list of countries with poliovirus outbreaks

A Pakistani health worker administers drops of polio vaccine to a child during a vaccination drive in Karachi on December 10, 2018. Pakistan is one of only two countries in the world where polio remains endemic.
Enlarge / A Pakistani health worker administers drops of polio vaccine to a child during a vaccination drive in Karachi on December 10, 2018. Pakistan is one of only two countries in the world where polio remains endemic.

The United States, one of the world’s richest and most developed countries, has met the World Health Organization’s criteria to be listed as a country with circulating vaccine-derived poliovirus, the Centers for Disease Control and Prevention announced Tuesday. of US Diseases

The United States now joins the ranks of about 30 other countries with polio outbreaks, mostly low- and middle-income, including Ethiopia, Mozambique, Somalia, and Yemen. Notably, the list includes only two other high-income countries, the UK and Israel, that have detected the circulation of a strain of poliovirus genetically linked to the one spreading in the US.

Specifically, the US met the criteria for the WHO list by documenting a patient with vaccine-derived poliovirus and having at least one environmental sample of vaccine-derived poliovirus. In July, New York’s Rockland County health officials reported a case of paralytic polio in an unvaccinated resident who had not traveled recently. Since then, New York officials and the CDC have monitored the spread of the virus in sewage and found 57 positive samples from four New York counties and New York City. The dates of the positive samples range from April to a recent sampling in August.

Inclusion on the WHO polio outbreak list is a new low point for the US. On the one hand, it reinforces a key global public health message in the drive to completely eradicate that virus, which is that “any form of poliovirus anywhere is a threat to children everywhere. But mainly it highlights the dangerous foothold that anti-vaccine sentiments have gained in the country over the past few decades.

The vast majority of the US population is vaccinated against polio and well protected against the dangerous disease. The CDC recommends that children receive three doses of inactivated polio vaccine at 24 months, followed by a fourth dose at ages 4 to 6 years. But vaccination rates have fallen in recent years, and small groups of states and counties can have surprisingly low coverage. For example, in Rockland County, just northeast of New York City, the vaccination rate for 2-year-olds was 67% in 2020, but is currently down to 60%. And according to zip code-level vaccination data, one area of ​​Rockland County has a vaccination rate as low as 37 percent, with a couple others in the 50s.

Vaccination challenges

Polio is a particularly important target for anti-vaccine misinformation. Much of the poliovirus currently circulating in the world, including in the US, is derived from oral vaccines, which use live, weakened poliovirus to stimulate immunity. Oral polio vaccines they are highly effective in protecting against paralytic polio and are safe and affordable. But, if used in areas with low vaccination rates, the harmless and immunizing vaccine viruses can be spread to others through poor sanitation and/or hygiene. If the vaccine continues to move from person to person, it may detect mutations along the way that allow it to regain the ability to cause infection and paralytic polio. At this point, the vaccine virus is reclassified as vaccine-derived poliovirus (VDPV).

VDPV’s circulation has been gobbled up by dangerous anti-vaccine advocates, such as Robert F. Kennedy Jr. and his organization, Children’s Health Defense, who giddily promote the false claim that polio vaccines cause polio. To be clear, polio vaccines are highly effective at safely preventing polio. As always, the lack of polio vaccination leads to polio outbreaks.

The US has not licensed or used oral polio vaccines since 2000. Instead, the US and many other high-income countries now use an inactivated polio vaccine, which does not include a live virus. However, a VDPV is what is spreading in the US The virus in the vaccine was probably brought to the US by someone vaccinated elsewhere. The disadvantage of using an inactivated vaccine is that it is not as potent as oral doses, which means that vaccinated people can still spread poliovirus, including VDPV, although they will be highly protected against paralytic disease.

CDC and New York officials are now trying to convince vaccine resisters to get vaccinated. Last week, New York Governor Kathy Hochul declared a statewide emergency in an effort to boost vaccination and surveillance efforts.

In a statement today, José R. Romero, director of the CDC’s National Center for Immunization and Respiratory Diseases, pressed that:

“Polio vaccination is the safest and best way to combat this debilitating disease and it is imperative that people in these unvaccinated communities get up to speed on their polio vaccinations immediately. We cannot stress enough that polio is a dangerous disease for which there is no cure.”

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