Herd immunity: What it means and could it help prevent COVID-19?


SAVANNAH, Ga. (WSAV) – Some may be familiar with the words “herd immunity.” President Donald Trump used the term just this week, saying it would make the coronavirus “disappear” over time, even without a vaccine.

How COVID-19 spreads is important when it comes to understanding herd immunity.

If you’ve tested positive for the coronavirus, health experts say you will probably infect at least two to three people. That’s COVID-19’s R-value or the rate it spreads.

“I get it, I give it to two people, those two people each give it to two people, that’s four, then eight,” said Dr. Lawton Davis, director of the Coastal Health District, “then 16, 32, then 64, and you’re off and you’re into exponential growth.”

To put it in perspective, the flu has an R-value of 1.2, while measles a highly infectious disease, is between 6 and 8.

Herd immunity happens when enough of a population is immune to a disease that it’s transmission slows or stops. Davis says how easy a virus spreads tells us what percentage of the population needs to be infected and recover to trigger mass immunity.

“At least 70 percent of the population probably needs to be immuned in order for herd immunity, or community immunity, to protect those people who would otherwise be vulnerable to it,” said Davis.

Davis says if we depend on herd immunity without a vaccine, a lot more people could die. The virus has already killed more than 6,400 Georgians.

He says our vulnerable population would suffer the most.

“That would completely overhelm our hospital system, we would be in a mess,” said Davis.

This week Trump appeared to support the idea. White House press secretary Kayleigh McEnany has since told reporters that “herd immunity has never been a strategy” for the Trump administration’s response to COVID-19.

Top health officials, including U.S. coronavirus task force members and Dr. Anthony Fauci, have strongly advised against the herd immunity strategy.

Davis says the vaccine is the safest path towards herd immunity. He says the good news is vaccine trials are showing promising results.

“People are developing both antibodies and then another arm of their immune system which is the T cells,” said Davis.

He says those who naturally develop immunity may not be protected forever. Some studies show it could last only a few months.

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