Polio vaccination rates in some areas of the US are dangerously close to the threshold required for herd immunity

(The conversation) – Given recent headlines, you might be wondering why polio is even an issue in 2022. Vaccines against the polio virus have been around for more than 60 years have practically all protected in the United States from the disease. Due to a hugely successful polio vaccination campaign that began in the 1950s when the first polio vaccines became availableuntil 1979 was polio considered extinct in the United States

Unfortunately, even today there are communities in the United States where polio vaccination rates are lower than needed. Because many people have not been vaccinated, there is now a real onePossibility of a polio resurgence in the US.

As aclinical professor of pharmacyI train future pharmacists on how vaccines work, how important they are and how they prevent diseases.

Longstanding concerns by public health experts about falling vaccination rates surfaced when in July 2022 a man from Rockland County, New York,was diagnosed with poliothe first such diagnosis in the United Statesin almost a decade. The patient – who developed the severe, paralytic form of the disease – had been exposed to onemodified live vaccine strain from overseas.

Then, on September 9, 2022, New York declared aEmergencydue to ongoing poliovirus transmission. At the time, officials had been investigating using sewage monitoring57 samples of poliovirus in wastewaterfrom four boroughs of New York. More than half of these were discovered in the same county where the adult patient is from, just outside of New York City.

As a result of continued poliovirus detection in wastewater, the Centers for Disease Control and Prevention said the US is now meeting World Health Organization criteria for “aCountry with circulating vaccine-derived poliovirus“The US has recorded its first case of polio in the US in almost a decade.

Two main types of poliovirus vaccines

There are two main types of polio vaccinesin use worldwide today. Thatinactivated poliovirus vaccineis given as a shot, and theoral attenuated (or weakened) poliovirus vaccinegiven as oral drops, sometimes on top of a sugar cube.

Since 2000, the US has exclusively used the inactivated poliovirus vaccine, which cannot cause disease because it contains no live virus. But in countries where the poliovirus continues to circulate,like Pakistan and Afghanistantheoral attenuated poliovirus vaccineis still used.

in theextremely rare cases, the live attenuated vaccine used in other countries can mutate back into its virulent form and cause paralysis. The adult in New York is said to have come into contact with the virus.

How “herd immunity” for polio is determined

The degree to which a community is protected from a pathogen like poliovirus boils down to thisherd immunity. When a community — known as the herd — reaches a threshold of immunity, it can prevent human-to-human transmission of a pathogen, thereby suppressing the pathogen.

The herd immunity threshold for a given disease is calculated based on the expected number of people that an infected person would transmit it to if they were susceptible. The higher the number of people who would become infected, the higher the percentage of the community or populationmust be vaccinatedto prevent further spread of the disease.

In the case of the polio virus, the researchers estimate that between five and seven people would be infected in each caseif these people were vulnerable. Based on these calculations, experts determined that at least 80% of a community or population should be vaccinated against the poliovirus to prevent its spread.

Declining vaccination rates

Polio vaccination rates vary widely in the United States.

The CDC recommends that infants and young children: aFour-dose schedule of inactivated poliovirus vaccineat 2 months, 4 months, 6 to 18 months and 4 to 6 years. For those who start vaccination later – as older children, adolescents or adults – three doses are considered a full vaccination. This is because three doses of an inactivated poliovirus vaccine have been shown to be effectivebetween 99% and 100% protection against serious diseases.

Although all U.S. states are currently above the 80% herd immunity threshold for poliovirus, there are areas within the country that are home to many unvaccinated or undervaccinated individuals – those who have not received a total of three lifetime doses of the inactivated vaccine.

For example, the state of New York has one of the highest immunization rates for polio in the country.with 97.9%of kindergarten children vaccinated in the 2020-2021 school year. But current estimates from the New York State Department of Public Health suggest so79% of 2-year-olds in this conditionreceived three doses of the polio vaccine.

Additionally, in certain pockets and counties of New York, such as Rockland, Orange, and Sullivan, three-dose vaccination rates can be far lower based on the 2-year-old age group, which is the only data available by county: Rockland 60%, Orange 59% and Sullivan 62%. In fact, 46% of New York counties are under the three-dose poliovirus vaccineHerd immunity threshold for 2 year olds. Most people today don’t remember the polio outbreak that terrorized Americans in the first half of the 20th century.

vaccination recommendations

When children are more than a month behind on the recommended polio shot, doctors recommend routine catch-up shots throughout adolescence.

Because most adults in the US today were vaccinated as children and thatThe US had eradicated polio from 1979there was little reason for health professionals to believe that an adult in the United States would be exposed to the poliovirus. For this reason, adult catch-up vaccination has not been included in the routine adult vaccination schedule.

But in August 2022, the CDC updated its guidelines. Given that there are communities where poliovirus vaccination rates have fallen below the 80% threshold required for herd immunity, and coupled with the continued spread of poliovirus in New York, the CDC is now recommending all unvaccinated or undervaccinated adults to do soreceive a poliovirus vaccination.

In addition, the CDC suggests that some fully vaccinated adults who are at increased risk of exposure could benefit from a one-time lifetime poliovirus booster dose. This includes healthcare providers caring for people with poliovirus or people traveling to areas where poliovirus has not been eliminated.

If you are unsure whether you need a vaccine or what steps you should take, talk to your pharmacist or doctor.

https://fox2now.com/news/national/polio-vaccination-rates-in-some-areas-of-the-us-hover-dangerously-close-to-the-threshold-required-for-herd-immunity/ Polio vaccination rates in some areas of the US are dangerously close to the threshold required for herd immunity

Sarah Y. Kim

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