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While the administration of two doses of the vaccine creates a strong immune response that reduces the risk of serious illness by more than 90%, the protection against milder and asymptomatic infections gradually wanes.
That is why Pfizer has applied for and received clearance from the United States Food and Drug Administration to add boosters for many people who are six months away from vaccination.
“I think we would expect immunity to slowly wane over time, but that’s not a reason for people to panic,” said Dr. Ann Falsey, viral respiratory disease specialist at the faculty. of Medicine from the University of Rochester.
“It’s not as if suddenly one day you are completely sensitive, like you were before you were vaccinated,” added Falsey, who helps lead clinical trials of Covid-19 vaccines.
“The vaccines all hold up fairly well – Pfizer, Moderna and Johnson & Johnson – for serious illness,” Falsey told CNN. “Now, that doesn’t mean we might not get to a point where we really need people to be reminded to prevent more serious illnesses. not the scary diseases we faced before. My main message is therefore not to panic. Everything will be alright.”
That hasn’t stopped Americans from flocking for boosters. Last week, more people received booster shots who were receiving their first set of coronavirus vaccines. By Friday, more than seven million Americans had received either booster shots of the third set of vaccines licensed for immunocompromised people who likely had not obtained adequate responses to the first two shots.
An Israeli study looked at 4,800 health workers and found that antibody levels declined rapidly after two doses of the vaccine, “especially in men, people 65 years of age or older, and people who are immunocompromised.”
A second study from Qatar showed that protection against the Pfizer vaccine peaked in the first month after vaccination and then began to decline.
“These results suggest that a large portion of the vaccinated population could lose their protection against infection in the months to come, possibly increasing the potential for further epidemic waves,” the team wrote in a report published in the New England Journal of Medicine.
How can protection weaken against mild or asymptomatic infection while remaining strong against severe disease?
This is because the human immune system is complex.
Antibodies form the first line of defense, preventing a virus from entering certain cells in the body. It is the protection that begins to wear off over time.
But there is a second line of defense: cellular immunity. Cells called B cells and T cells may take longer to generate than antibodies, but they offer a longer and broader defense against infections and are responsible for decreasing serious infections.
So while people may be susceptible to mild illness after being vaccinated, they are much less likely to get really sick, end up in the hospital, or die.
“But there are a lot of reasons people don’t want to get sick. They don’t want to pass it on to their loved ones. People don’t want to pass it on to young children who cannot yet get vaccinated,” he said. Falsey said. .
The United States Centers for Disease Control and Prevention has been saying for months that this is why even fully vaccinated people should continue to take infection precautions – wear masks when surrounded by many other people who may or not be vaccinated, especially indoors, and keep rooms well ventilated.
“They just don’t have to storm the drugstores and panic.”
People receiving boosters now should have been among the first to be vaccinated – in January, February and March. These are people 65 years of age and over, adults with conditions that put them at risk of serious illness, and people in jobs or living conditions that put them at greater risk of infection than usual. mean.
Everyone should chill it for now.
“They just don’t need to storm pharmacies and panic,” Falsey said.
People shouldn’t go ahead and get booster doses if it’s not been six months since their last dose of Pfizer vaccine because they won’t get the best immune response, Fauci said in a briefing. at the White House last month.
“There will be temptations, for example, for people recently vaccinated not to wait for the six-month period,” Fauci said. But waiting several months after the initial vaccination for stimulation helps produce a stronger response. The cells of the immune system that help restore declining immunity respond more vigorously if they are allowed to enter a state of rest after the first round of vaccination.
That said, most people should eventually plan to get boosters, Falsey said.
“This will probably be true for all vaccines, not just Pfizer – we will benefit from a boost in immunity. This is not the same as saying it’s absolutely necessary,” she said. declared.
Although people who have recovered from an infection have some protection, they are even more protected if they are also vaccinated.
“I think, depending on your own natural immunity because you feel like a strong person, it’s like playing Russian roulette,” Falsey said.
Even young, apparently healthy people have fallen seriously ill from Covid-19 and died from it.
“I would never depend on my natural immunity alone to resist this virus. He’s a very, very bad actor,” Falsey said.
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