{"id":190536,"date":"2022-09-27T07:01:14","date_gmt":"2022-09-27T11:01:14","guid":{"rendered":"https:\/\/today.uconn.edu\/?p=190536"},"modified":"2022-09-22T10:40:26","modified_gmt":"2022-09-22T14:40:26","slug":"polio-vaccination-rates-in-some-areas-of-the-us-hover-dangerously-close-to-the-threshold-required-for-herd-immunity-heres-why-that-matters-2","status":"publish","type":"post","link":"https:\/\/today.uconn.edu\/2022\/09\/polio-vaccination-rates-in-some-areas-of-the-us-hover-dangerously-close-to-the-threshold-required-for-herd-immunity-heres-why-that-matters-2\/","title":{"rendered":"Polio Vaccination Rates in Some Areas of the US Hover Dangerously Close to the Threshold Required for Herd Immunity \u2013 Here\u2019s Why that Matters"},"content":{"rendered":"

Given recent headlines, you may be wondering why polio is even an issue in 2022. For more than 60 years, vaccines against the poliovirus\u00a0have protected virtually everyone<\/a>\u00a0in the United States from the disease. Due to an enormously successful polio vaccination campaign beginning in the 1950s when the\u00a0first polio vaccines became available<\/a>, by 1979 polio was\u00a0considered eliminated in the U.S.<\/a><\/p>\n

Unfortunately, even today, there are communities in the U.S. that have lower-than-necessary polio vaccination rates. Because many people have not been vaccinated, there is now a real\u00a0possibility of a resurgence of polio in the U.S<\/a>.<\/p>\n

As a\u00a0clinical professor of pharmacy<\/a>, I train future pharmacists about how vaccines work, their importance and how they prevent diseases.<\/p>\n

Public health experts\u2019 longstanding concerns over falling vaccination rates rose to the surface when, in July 2022, a man from Rockland County, New York,\u00a0was diagnosed with polio<\/a>, the first such diagnosis in the U.S.\u00a0in nearly a decade<\/a>. The patient \u2013 who developed the severe, paralytic form of the disease \u2013 had been exposed to an\u00a0altered live vaccine strain from overseas<\/a>.<\/p>\n

Then on Sept. 9, 2022, New York declared a\u00a0state of emergency<\/a>\u00a0due to ongoing poliovirus transmission. As of that date, using wastewater surveillance, officials had identified\u00a057 samples of poliovirus in wastewater<\/a>\u00a0from four New York counties. More than half of those were detected in the same county where the adult patient is from, just outside New York City.<\/p>\n

As a result of the continued poliovirus detection in wastewater, the Centers for Disease Control and Prevention declared that the U.S. now meets the World Health Organization\u2019s criteria for \u201ca\u00a0country with circulating vaccine-derived poliovirus<\/a>.\u201d<\/p>\n

Two main poliovirus vaccine types<\/strong><\/p>\n

There are two key types of polio vaccine\u00a0in use around the world today<\/a>. The\u00a0inactivated poliovirus vaccine<\/a>\u00a0is given as a shot, and the\u00a0oral attenuated (or weakened) poliovirus vaccine<\/a>\u00a0is administered as oral drops, sometimes on a sugar cube.<\/p>\n

Since 2000, the U.S. has exclusively used the inactivated poliovirus vaccine, which cannot cause disease since it does not contain live virus. But in countries where the poliovirus continues to circulate,\u00a0such as Pakistan and Afghanistan<\/a>, the\u00a0oral attenuated poliovirus vaccine<\/a>\u00a0is still used.<\/p>\n

In\u00a0extremely rare cases<\/a>, the weakened live vaccine used in other countries can mutate back into its virulent form and lead to paralysis. This is how the adult in New York is believed to have come into contact with the virus.<\/p>\n

How \u2018herd immunity\u2019 for polio is determined<\/strong><\/p>\n

The degree to which a community is protected from a pathogen like poliovirus comes down to\u00a0herd immunity<\/a>. When a community \u2013 the so-called herd \u2013 reaches a threshold of immunity, it can prevent the transmission of a pathogen from person to person, thereby quelling the pathogen.<\/p>\n

The herd immunity threshold for a given disease is calculated based upon the expected number of individuals who an infected person would spread it to if they were susceptible. The higher the number of individuals who would become infected, the higher the percentage of the community or population that\u00a0needs to be vaccinated<\/a>\u00a0to avoid continued spread of the disease.<\/p>\n

For poliovirus, researchers estimate that between five and seven individuals would be infected for each case\u00a0if those people were susceptible<\/a>. Based upon these calculations, experts determined that at least 80% of a community or population should be vaccinated against poliovirus to prevent its spread.<\/p>\n

\"The
The iron lung on display as part of the Dolan collection at the Widmer Wing of Storrs Hall on April 23, 2018. (Peter Morenus\/UConn Photo)<\/figcaption><\/figure>\n

Falling vaccination rates<\/strong><\/p>\n

Throughout the U.S., vaccination rates for polio vary significantly.<\/p>\n

The CDC recommends that infants and young children receive a\u00a0four-dose schedule of the inactivated poliovirus vaccine<\/a>\u00a0at 2 months, 4 months, 6 to 18 months and 4 to 6 years. For those who begin vaccination later \u2013 as older children, teens or adults \u2013 three doses is considered to be complete vaccination. This is because three doses of inactivated poliovirus vaccination have been shown to provide\u00a0between 99% and 100% protection against severe disease<\/a>.<\/p>\n

Although all U.S. states are currently above the 80% herd immunity threshold for poliovirus, there are areas within the country that include many pockets of unvaccinated or undervaccinated individuals \u2013 those who have not received a total of three lifetime doses of the inactivated vaccine.<\/p>\n

New York state, for example, holds one of the highest kindergarten polio vaccination rates in the country,\u00a0with 97.9%<\/a>\u00a0of kindergartners vaccinated in the 2020-2021 school year. But current estimates by the New York State Department of Public Health suggest that only\u00a079% of 2-year-olds in that state<\/a>\u00a0have received three doses of the polio vaccine.<\/p>\n

Further, in certain pockets and counties of New York, such as Rockland, Orange and Sullivan, three-dose vaccination rates may be far lower based on the 2-year-old age group, which is the only data that is available by county: Rockland 60%, Orange 59% and Sullivan 62%. In fact, 46% of counties in New York are below the three-dose poliovirus vaccination\u00a0herd immunity threshold for 2-years-olds<\/a>.<\/p>\n

Vaccine recommendations<\/strong><\/p>\n

When children fall more than one month behind on recommended polio vaccination, doctors recommend routine catch-up throughout adolescence.<\/p>\n

Because most adults in the U.S. today were vaccinated as children and the\u00a0U.S. had eliminated polio as of 1979<\/a>, there was little reason for health experts to believe an adult would come into contact with poliovirus in the U.S. For that reason, catch-up vaccination for adults has not been included on the routine adult vaccination schedule.<\/p>\n

But in August 2022, the CDC updated its guidelines. In light of the fact that there are communities where poliovirus vaccination rates have fallen below the 80% threshold needed for herd immunity, coupled with the ongoing circulation of poliovirus in New York, the CDC now recommends that all unvaccinated or undervaccinated adults\u00a0receive a poliovirus vaccination<\/a>.<\/p>\n

Additionally, the CDC suggests that some fully vaccinated adults who are at increased risk of exposure may benefit from a single lifetime poliovirus booster dose. This includes health care providers who care for those with poliovirus, or people traveling to areas where poliovirus has not been eliminated.<\/p>\n

If you are unsure if you need vaccination or what steps you should take, talk to your pharmacist or primary care physician.<\/p>\n

 <\/p>\n

Originally published in The Conversation.<\/a><\/em><\/p>\n","protected":false},"excerpt":{"rendered":"

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