As people across the world grapple with the prospect of living with the coronavirus for the foreseeable future, one question looms large: How soon before they need yet another shot?
Not for many months, and perhaps not for years, according to a flurry of new studies.
Three doses of a Covid vaccine — or even just two — are enough to protect most people from serious illness and death for a long time, the studies suggest.
“We’re starting to see now diminishing returns on the number of additional doses,” said John Wherry, director of the Institute for immunology at the University of Pennsylvania. Although people over 65 or at high risk of illness may benefit from a fourth vaccine dose, it may be unnecessary for most people, he added.
Federal health officials have said they are not planning to recommend fourth doses anytime soon.
The Omicron variant can dodge antibodies — immune molecules that prevent the virus from infecting cells — produced after two doses of a Covid vaccine. But a third shot of the mRNA vaccines made by Pfizer-BioNTech or by Moderna prompts the body to make a much wider variety of antibodies, which would be difficult for any variant of the virus to evade, according to the most recent study, posted online on Tuesday.
The diverse repertoire of antibodies produced should be able to protect people from new variants, even those that differ significantly from the original version of the virus, the study suggests.
“If people are exposed to another variant like Omicron, they now got some extra ammunition to fight it,” said Dr. Julie McElrath, an infectious disease physician and immunologist at Fred Hutchinson Cancer Research Center in Seattle.
What’s more, other parts of the immune system can remember and destroy the virus over many months if not years, according to at least four studies published in top-tier journals over the past month.