When will Ohio reach herd immunity?

Posted at 9:28 AM, Mar 30, 2021
and last updated 2021-03-30 11:15:11-04

COLUMBUS, OH — As the COVID-19 pandemic enters its second year, many are left wondering: When will the pandemic be declared over?

Health organizations and medical experts have suggested the pandemic will be over when the U.S. reaches herd immunity. A New York Times projection has this happening for the U.S. sometime between May and October.

But when will Ohio reach herd immunity?

The World Health Organization defines herd immunity as when “a substantial portion” of a population is immune to a disease. Some diseases, like measles, require 95% of the population to have immunity to reach herd protection, according to the WHO.

The percent of the population needed to reach herd immunity for COVID-19 is unknown, but is thought to be 60-80% of the population. But with new variants of the virus emerging, the herd immunity threshold could be higher, said Dr. Michael Oglesbee, director of Ohio State’s Infectious Disease Institute.

“Initial estimates were around 60 percent, but I think with some of the new variants, maybe we need to get up to somewhere in the 80 percent range,” Oglesbee said.

Using an estimate of 70 percent for herd immunity and with current vaccination trends provided to WCPO by the Ohio Department of Health, most Ohioans will have at least one vaccination for COVID-19 by the beginning of July. It will, however, take longer for Ohio to reach full immunity.

Using this data, 70% of Ohioans will have some COVID-19 immunity from a vaccine on July 7.

However, there is a substantial portion of Ohio’s population that likely already has partial or full immunity to COVID-19. These are the one million confirmed COVID cases, and the suspected three million total cases, according to the Ohio Department of Health.

According to the CDC, there may be two to five times as many COVID cases than have been officially reported. Using a conservative estimate of there being three times as many COVID cases in Ohio than have been reported, we reach around three million people with some or full immunity.

Factoring in these immune people and the rate of completed vaccinations, a new timeline can be created.

Ohioans with full immunity

With just the current rate of vaccine completion alone, it wouldn’t be until Oct. 27 that Ohio reaches 70 percent of the population with full immunity. When suspected cases are added to those that are fully vaccinated, that date gets pushed forward to July 5.

A prolonged vaccination effort could actually weaken Ohio’s chances for herd immunity, and so it is important that vaccines are given as fast as possible, Oglesbee said.

“The longer this draws out, the more we’re going to see immunity wane," Oglesbee said. "So, say I was infected three months ago. I wasn’t. I’m just setting up a scenario. If I had been infected three months ago, with time my immunity is going to diminish and I can once again become susceptible. And so that magic number of 60-80 percent becomes more elusive.”

So, assuming that vaccination rates, infection rates and supply remain relatively steady, it looks like July might be the beginning of herd immunity to COVID-19 in Ohio. This date can change due to fluctuations in vaccination or new variants, but it looks like the summer may be the beginning of herd immunity in Ohio.