American food and the Drug Administration is pushing for you to get an annual Covid booster. The problem is that the data does not specify if you need it.
Covid is not going anywhere. In the United States and many European countries, SARS-CoV-2 is still circulating at significant levels, with Covid establishing itself as a major and continuing cause of illness. Boosters may protect against its worst effects, but they are shots in the dark: insurance against serious illness, but perhaps not necessary. This is because we don’t know how long their protection against serious diseases actually lasts.
It’s time we knew that, but it means changing direction. At a basic biology level, this means paying less attention to vaccine-generated antibodies and focusing more on another very important but overlooked part of the immune system: memory T cells. “The way you’re going to know who needs boosters is by knowing how long memory cells last,” says Paul Offit, a professor of vaccinology at the University of Pennsylvania and a vaccine adviser to the FDA.
The immune system is complex, but it basically has three parts. There is innate immunity, the physical or chemical barriers, such as your skin or the mucus in your nose, that are constantly working to ward off disease-causing microbes.
For germs that exceed this, then there is short-term or humoral immunity: the rapid response tailored to a particular invasive threat, such as a virus, that dominates soon after it arrives to try to prevent an infection from taking hold. . This defensive wave is led by neutralizing antibodies specially designed to fight whatever has invaded the body.
But when this antibody response fails to prevent Covid from taking hold and the virus gets inside cells to reproduce, a third protective component comes into play: long-term cellular immunity. Memory T cells, which are also adapted to the specific threat, are a key part of this.
“Once a virus infects cells, T cells can then limit the amount of viral replication,” says Céline Gounder, infectious disease specialist and editor of KFF Health News. When a virus like Covid reproduces, it parks parts of itself in the outer membrane of the cell, which tells the host that the cell is infected. T cells – primed, by vaccination or previous infection, to notice these strange parts – then kick into gear, killing the infected cells and directing the production of more antibodies. “It stops the disease from progressing,” says Gounder.
So while cellular immunity doesn’t stop an initial infection, it’s what keeps people away from the hospital, intensive care unit and morgue, says Offit. “The second thing that’s good is that T cells often live for years, decades, or lifetimes,” he says, meaning the protection they provide against serious disease can be long-lasting. duration.
And there is a third major advantage. In Covid, some of the viral fragments that end up on cell membranes and attract T cells are “highly conserved” interior parts of the coronavirus – fragments that are much less likely to mutate and become invisible to the immune system. Proteins that coat the outside of the virus, which usually end up being targeted by antibodies, are much more likely to mutate, leaving those antibodies less effective.