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Doctor at Johns Hopkins warns against herd immunity by infection

Posted at 1:13 PM, Aug 28, 2020

To end the pandemic, there need to be enough people immune to COVID-19 and there are two ways to do that: immunity through infection or from a vaccine.

"I think racing to herd immunity is the dangerous thing that I’m concerned about," said Dr. Stuart Ray, a professor of medicine at Johns Hopkins University School of Medicine.

Herd immunity is when the spread of the infection cannot be sustained because the number of people who are immune is high enough. Some countries are considering it as a strategy to combat COVID-19.

But Ray said it could not work in the US unless much more effective treatments are developed.

He says on average, a newly infected person infects two others, so to have herd immunity from COVID-19 about 60 percent of people would have to become immune.

"We would have something like another 100 million people, maybe more, infected. 150 million more and even if the major complication rate is a fraction of 1 percent, we will still have huge numbers of deaths," said Ray.

He said we also don’t know if just having had the infection once will create lasting immunity to control the spread.

"It possible that you could be immune enough not to get sick and still not immune enough to prevent that spread and so herd immunity is a tough bar for us to aim for because not only do we need 60 percent of people to be immune but we need them to be immune in a way that prevents them from infecting other people," said Ray.

The other way to achieve herd immunity would be through a vaccine.

"Vaccines can work better, provide better immunity than the natural infection does. The new shingles vaccine provides great immunity and protects more than 95 percent of people from getting shingles," said Ray.

Several vaccines are still going through the last phase of clinical trials to see if any also creates enough immunity to prevent passing the virus along.

This story was first reported by Abby Isaacs at WMAR in Baltimore, Maryland.