Herd immunity refers to when a population has immunity from a disease either through vaccination or recovery. Some health experts hope to reach herd immunity against COVID-19 in the United States. But people should keep in mind that reaching herd immunity does not mean that a disease has gone away, Dr. Jay Bhattacharya told The Epoch Times.
The concept is built on how many people each person who contracts a disease transmits that disease to, with people with some immunity infecting fewer people, on average.
“So if I get COVID, I only infect one person or fewer than one person on average and what that means is that the disease will decrease in prevalence, so that whenever the case counts are coming down, you’re actually in herd immunity,” Bhattacharya, a professor of medicine at Stanford University, said on The Epoch Times’ “American Thought Leaders.”
“Herd immunity is not a synonym for zero COVID. I think that is the problem that many people have had in thinking about herd immunity. It’s not a synonym for ‘the disease has gone away, we never have to think about it again,’” he added.
Top health experts have differed on the percentage of people needing immunity to achieve herd immunity in a certain population. Dr. Anthony Fauci, said last year that a floor of 60 percent immunity would be required, but later gave a range of up to 90 percent.
Experts say both vaccines and so-called natural immunity, or the immunity enjoyed post-recovery, contribute to herd immunity. But COVID-19 vaccines, which were initially touted as preventing infection, have sharply waned in effectiveness against infection over time.
“They continue to work well with [the] Delta [variant] with regard to severe illness and death, but what they can’t do anymore is prevent transmission,” Dr. Rochelle Walensky, the director of the Centers for Disease Control and Prevention, said on CNN over the summer.
That makes natural immunity the more important piece, according to Bhattacharya, even as federal health officials like Fauci and Walensky focus on vaccinations.