Tennessee’s low COVID-19 vaccination rate makes herd immunity less accessible; here’s why it’s important


Tennessee’s low COVID-19 vaccination rate threatens more than those who choose not to be vaccinated, which is why healthcare and scientific communities are pushing for more education and efforts to combat it. reluctance to vaccinate in order to get more shots in the arms.

“My grave concern is that if people don’t appreciate the continued toll this pandemic is taking on our country and recognize the benefits of vaccination, our ability to achieve this state of so-called ‘herd immunity’. “Is uncertain,” infectious disease specialist Dr Jay Sizemore said at an Erlanger Health System board meeting on Thursday.

“Collective immunity” occurs when a large enough portion of the population is immune to an infectious disease to provide indirect protection to others who are not immune. This is because the circulation of the disease stops when there are not enough susceptible people left to infect.

Immunity can be obtained by vaccination or a previous infection. However, vaccination is always preferred. Vaccines prevent more deaths, disease and the possibility of disease spread, and herd immunity to disease has never been achieved without a vaccine.

The collective immunity threshold differs depending on the disease and depends on its degree of infection. Measles, one of the most contagious diseases in the world, requires vaccination of around 95% of the population, while the threshold for polio is around 80%, according to the World Health Organization.

These thresholds are important because some people will never be able to be vaccinated due to health problems, and these diseases will start to resurface if vaccination levels fall below these rates.

In the year leading up to the pandemic, measles and polio both experienced a resurgence around the world due to declining vaccination rates.

Polio has remained officially eradicated in the United States since 1979 thanks to a successful vaccination program, but there were nearly 1,300 cases of measles from January 1, 2019 to December 31 – the highest number in the United States in 27 years.

(READ MORE: Measles and other infections had a big year in Hamilton County, US)

The ability to achieve herd immunity also depends on the duration of immunity against a disease. Even though measles is highly contagious, immunity lasts a lifetime, reaching the high bar of the immunization rate of 95%.

It is not known how many people need to be vaccinated against COVID-19 to achieve herd immunity, but scientists estimate the threshold to be around 70%.

Robert Bednarczyk, assistant professor of global health at the Rollins School of Public Health at Emory University, said getting as many people vaccinated as possible was more important than focusing on a percentage. Indeed, other factors, such as population density and vaccination levels of surrounding communities, all have an impact on herd immunity.

“If 70% of those vaccinated live in a small area of ​​a county and the other large parts of that county are not vaccinated, this is a large group of people potentially at risk and who may not be harvesting the benefits of this herd immunity, ”said Bednarczyk.

Although part of the population is protected from COVID-19 by a previous infection – protection that lasts around eight months and possibly longer – vaccination levels in the Chattanooga area are nowhere near close enough to achieve herd immunity.

Meigs County leads the region in terms of vaccination rates with 17.4% of its population fully vaccinated, followed by Hamilton County with 14%. Grundy County’s vaccination percentage is the lowest, with just 7.8% of the population fully vaccinated.

Still, Sizemore remains optimistic.

“I think we have the possibility of obtaining collective immunity,” he said. “I think we have a long way to go.”

Contact Elizabeth Fite at [email protected] or follow her on Twitter @ecfite.

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