Future Cycle of Boosters
“Most vaccines that are given in the U.S. require several doses to render immunity,” says Jason C. Gallagher, clinical professor at Temple University’s School of Pharmacy and clinical specialist in infectious disease. “I also like to think of [a COVID-19 vaccine booster] as the third dose of a multi-dose series.”1
This is because most vaccines without a live, attenuated virus, like the COVID-19 vaccines, typically require multiple doses or boosters.
Since both COVID-19 and its vaccines are new, we are still learning about the duration of protection offered by the shots.
Most data suggests the vaccines offer reduced protection against different strains of COVID-19, such as the Delta and Omicron variant.
Are Covid boosters going to be a permanent fixture in the future?
Probably, but we do not know for sure.
Scientists are still investigating how strong the current vaccines' protection are against new variants.
In its natural state, your body is exposed to thousands of bacteria and makes antibodies accordingly. Vaccines use the same natural processes to help the immune system build these antibodies safely against more dangerous viruses, like COVID-19.2
But vaccines aren't fool-proof and viruses evolve.
Ali Ellebedy, an associate professor of pathology and immunology at Washington University in St. Louis, is studying the lymph nodes and bone marrow of individuals vaccinated against COVID-19.
He was surprised how long the first two doses of the mRNA vaccine influenced immune systems. Six months after the second shot, the reaction continues to mature.
“There is an ongoing reaction in our lymph nodes that’s going for six months. And that reaction, we are showing, that it is actually enhancing the potency of the antibodies,” said Ellebedy. “Even before the third dose.”3
Six months between the first round of shots and the booster, there is a boosting of the immunity from the first vaccine, and a broadening of the immune response, in order to recognize other variants.
“Your immune response becomes much more cross-protective,” said David Topham, an immunologist at the University of Rochester Medical Center and director of the New York Influenza Center of Excellence.
Antibodies induced by delayed third doses are of higher quality, which generate a wider immune response that is able to recognize mutated viruses and new variants.
“Once you give the [antibody-producing] B cells a chance to mature and then boost them later…that type of response tends to make immunity across all these different variants more similar," said Barney Graham,an immunologist and deputy director of the National Institutes of Health's Vaccine Research Center until his retirement in August.4
“So, I think that the whole question about durability of immunity is going to have to be determined by three years from now, are people still getting sick or are they relatively well-protected against severe disease — regardless of whatever their antibody level is in serum. Because that may wane, but you still have a lot of memory B cells that can rapidly respond,” Graham said.
The early estimates of the efficacy of the mRNA vaccines to prevent infections — in the 95% range — created unrealistic expectations about what COVID-19 vaccines would be able to do over the long-term in blocking infections.
Vaccines make hospitalization and death less likely, but their efficacy falls over time so people vaccinated in April, as an example, are quite susceptible.5
As months pass from vaccination, neutralizing antibody levels have declined and breakthrough infections among the vaccinated have increased, a phenomenon that seems to be accelerating with the Omicron variant.
The vaccines have worked in reducing hospitalizations and deaths, but boosters seem to be necessary to continue efficacy; and only time will tell if boosters are necessary on a continued, regular basis.
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