![]() ![]() ![]() That unseen mechanism was what scientists call cellular immunity, and its foot soldiers are T cells.ĭr. But they weren’t becoming severely ill or dying at nearly the same rate as people who had no immune protection. People who’d been vaccinated or previously infected were coming down with COVID-19. ![]() Over time, it became clear that antibodies alone weren’t telling the whole story of Americans’ immunity. ![]() But that renewal process takes time, and the Delta and Omicron variants proved adept at establishing infections before the body’s defenses are in place. Once enough Americans were vaccinated, the reasoning went, antibodies would block so many infections that the coronavirus would just die out for lack of new victims to infect.īut as the pandemic unfolded, hopes of reaching this state of “herd immunity” were dashed.Īll virus-specific antibodies “decay” with time, leaving behind a template to make more when needed. The more antibodies, the more thorough their protections.įor a while, officials hoped high levels of antibodies would drive the virus out of circulation altogether. Toting up the immune proteins that form in the wake of vaccination or infection is one way to assess how quickly a person could be expected to block or clear an infection. It’s easy and inexpensive to do with lab tests that are readily available. Scientists have one measure of immunity that’s backed by decades of research - counting antibodies. The pandemic virus’ knack for delivering surprises makes scientists wish they understood COVID-19 immunity well enough to anticipate its next move. Cody Meissner, a Dartmouth College pediatric infectious disease physician who’s on the FDA’s advisory panel for vaccines. Hospitalizations for COVID-19 have plummeted, and weekly deaths from COVID-19 have fallen 90% from their most recent peak just over a year ago.īut that’s just “a snapshot in time,” said Dr. Hayley Gans, a Stanford infectious disease doctor who advises the Food and Drug Administration on vaccine policy, said in a recent public meeting convened by the agency. “We’re always at the point of having to make decisions without that data,” Dr. ![]()
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