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A sign promotes booster doses in front of a COVID-19 vaccination center in Revere, Massachusetts, on December 21, 2021. (M. Scott Brauer / The New York Times)
of a few months?
Repeatedly alerted by a virus that has defied expectations, scientists are reluctant to predict the future. But in various interviews this week, about a dozen of them said that whatever happens, trying to get the entire population to get boosted again after a few months is unrealistic. It also doesn’t make much sense from a scientific point of view.
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A fire department-run vaccination clinic in San Ramon, California, on December 16, 2021. (Jim Wilson / The New York Times)
“It’s not crazy to give vaccinations on a regular basis, but I think there are better ways than to give boosters every six months,” said Akiko Iwasaki, an immunologist at Yale University. Other strategies, he said, could “get us out of this kind of eternal backup situation.”
To begin with, convincing the population to line up for booster doses after a few months is a failed proposition. About 73 percent of American adults have the full vaccination schedule, but just over a third of them have decided to get a booster dose so far.
“This certainly does not appear to be a sustainable long-term strategy,” said Deepta Bhattacharya, an immunologist at the University of Arizona.
Also, just as important is the fact that there is no data to support the effectiveness of a fourth dose of current vaccines (the calculation is different for people with compromised immune systems, who might benefit from a fourth dose).
Pfizer-BioNTech, Moderna and Johnson & Johnson have said they are testing omicron-targeted vaccines that could be available within a few months.
“There is no point in continuing to reinforce against a variant that has already faded,” said Ali Ellebedy, an immunologist at the University of Washington, San Luis campus. “If you are going to apply an additional dose after three, I would certainly wait for one specialized in the omicron variant.”
If the goal is to boost immunity against omicron or future variants, experts say there are other tactics that would be more effective than continually giving booster doses of a vaccine designed to recognize the parent virus.
Some research teams are developing a vaccine dubbed “pancoronavirus” designed to attack parts of the virus that do not change or change very slowly.
Current vaccines could be combined with boosters from nasal or oral vaccines, which are more effective at preventing infections because they coat the nose and other mucosal surfaces – the entry points for the virus – with antibodies.
In addition, simply allowing more time to elapse between vaccine doses may also strengthen immunity. This is a lesson that scientists learned in various battles against other pathogens.
Many experts were initially opposed to the idea of a booster dose. Some believed that the original vaccine regimens were sufficient to keep the majority of the population away from hospitals and that this must be the true measure of a vaccine’s success.
Others felt it was unfair for rich countries to hoard the booster vaccine when millions of people around the world had not yet received their first dose.
But the perspective changed when scientists saw the fast and relentless march of the omicron variant around the world. “The omicron really changed my mind about it,” said Scott Hensley, an immunologist at the University of Pennsylvania.
“People who are vaccinated are actually doing very well in avoiding hospitalizations,” said Michel Nussenzweig, an immunologist at Rockefeller University in New York. The omicron has made it clear that preventing all infections is a lost cause, he added.
If vaccines prevented infection and the spread of the virus, regular boosters might make sense. “But with the existence of the omicron, what’s the point?” Said Nussenzweig. “The bottom line here is to prevent people from requiring hospitalization.”
Last fall, Anthony Fauci, America’s top adviser on the pandemic, spoke repeatedly about the importance of preventing symptomatic infections. But in recent days, he has also begun to affirm that the fundamental thing is to avoid hospitalizations.
To prevent infection, booster doses must be in near perfect timing with the circulation of a variant in the population. For example, many people who received a third dose in early fall were left vulnerable to omicron because their immune boosts had already waned.
Generally, people are advised to get a flu shot just before the virus begins to circulate during the winter. If the coronavirus ends up settling in a seasonal flu-like pattern, which is quite possible, “we could imagine a scenario where we just apply boosters before winter every year,” Hensley said.
Some experts have expressed concern that being boosted too often – as some people do on their own – could even be harmful. In theory, there are two ways it could backfire.
Most immunologists now dismiss as unlikely the first possibility, in which the immune system is depleted by repeated stimulation – a condition called “anergy” – and stops responding to coronavirus vaccines. “We’re not really detecting the presence of these strange memory cells that are indicative of anergy or dysfunction,” Bhattacharya said.
The second concern, called “antigenic original sin,” seems more plausible. From this point of view, the response of the immune system adapts to the first version of the virus, so its responses to later variants are much less powerful.
With more than 50 mutations, omicron is different enough from previous variants that antibodies made for the original version have difficulty recognizing the newer version.
“We have enough clues that it could be a problem,” said Amy Sherman, a vaccine expert at Harvard University. “Without a doubt, we have seen an evolution in a short period.”