It’s Too Soon for Annual Covid Booster Shots, Some Experts Say

It’s too early to tell if the US population will need annual Covid-19 booster shots, infectious disease doctors say. They say they don’t yet know how best to respond to the unpredictable patterns of new variants.

But a “regular cadence” of annual Covid-19 shots in line with flu shots would “get more people to get into a rhythm of keeping up to date,” Anthony S. Fauci, President Joe Biden’s former chief medical adviser, said in an interview.

A panel of 21 advisers to the Food and Drug Administration Jan. 26 recommended making bivalent Covid-19 shots the standard form of the vaccine. They also discussed the FDA’s proposal to assess the latest Covid-19 variants “at least annually,” similar to the process for developing annual flu shots. Under the plan, the Vaccines and Related Biological Products Advisory Committee would meet in early June to discuss which strains should inform shots to be administered in the fall.

Currently, about 15% of the total US population have received the bivalent booster shot that came out last September, with 69% having completed their primary vaccinations, according to data from the Centers for Disease Control and Prevention.

Infectious disease specialists agree on the need for a regular, periodic evaluation of the circulating Covid-19 variants, especially as the national health emergency is set to end in May. But some argue it may not be time just yet to establish a yearly schedule of updating and distributing Covid-19 vaccines, in part because variants change quickly and don’t fall into predictable seasonal patterns. They argue more clinical and epidemiological data is needed over time to measure infection patterns and how long it takes for the protection from existing vaccines to wane against new variants.

“It’s really premature for us to say, ‘this is what we’re going to do every year,’” Archana Chatterjee, dean of the Chicago Medical School at Rosalind Franklin University and member of the FDA’s vaccine advisory panel, said in an interview.

“That may become more apparent as time goes on, but as of now, we are not in a place to say, ‘this is going to be an annual thing,’” she added.

Advisers plan to meet in early summer to develop recommendations for vaccines this coming fall. Looking ahead, researchers argue that the focus should be on developing better surveillance of the virus as it continues to evolve, as well as research on next-generation vaccines that can tackle a wide range of potential variants.

‘This Is Not Influenza’

The infrastructure for monitoring influenza and its variants is largely based on its seasonal pattern. Officials in the Northern Hemisphere can choose strains for annual shots based on the dominant ones from the Southern Hemisphere’s winter season.

But the virus that causes Covid-19 isn’t as predictable. The delta variant led to a Covid-19 surge in the summer of 2021, and the omicron strain emerged that winter, ushering in a variant that’s proven to be very different from the previous versions of the coronavirus.

“This is not influenza,” Chatterjee said. “It’s a virus that behaves in a very different way.”

The virus changes rapidly, so variants identified earlier in the year for an annual Covid shot may not be adequately equipped to protect against a variant that pops up that fall or winter, said Davidson Hamer, a professor of global health and medicine at Boston University.

“If they try and decide by June, you could be using data from maybe March through May or March through June,” Hamer said. “Is that going to necessarily reflect what happens three to six months later?”

The proposed early June timeline for annual strain selection is more of a “placeholder” right now, Jerry Weir, director of the division of viral products in the FDA’s Center for Biologics Evaluation and Research (CBER), said in the latest advisory committee meeting. “We may have to go back and rethink this as far as the timing.”

More Data Needed

The safety and efficacy data that needs to be collected on updated shots, as well as regulatory review and manufacturing, can prolong the time between identifying circulating strains and getting updated shots into arms, infectious disease specialists say.

“I cannot see them changing it in time quickly enough every year,” said Monica Gandhi, a professor of medicine at the University of California, San Francisco, who specializes in infectious diseases.

The mRNA technology allows shots like the ones from Pfizer Inc. and Moderna Inc. to be developed faster than traditional vaccines, but “you still need months in order to make the vaccine, make enough bulk, and enough doses of that,” said Angela Shen, a visiting scientist at the Children’s Hospital of Philadelphia and a former officer at the US Department of Health and Human Services.

It’s also not clear right now the level of antibodies one needs to be protected from severe disease, and exactly how long this protection lasts as new variants emerge. This data can help determine how often a person needs to get another Covid-19 shot, which can vary depending on one’s age or any underlying conditions, Chatterjee said.

“When it comes to the elderly or those whose immune systems are compromised, or who have immature immune systems like children do, we don’t know enough to say, ‘these folks need more frequent boosting versus others that don’t,’” she said.

Next-Generation Shots

The ever-changing nature of the coronavirus is also fueling a push to look beyond chasing the next potential variant, and focus more on next-generation vaccines that could target multiple strains.

Since September 2021, the National Institute of Allergy and Infectious Diseases has awarded millions of dollars to seven research sites looking at developing a “pan-coronavirus” vaccine capable of fighting a diverse group of coronaviruses and variants.

CBER Director Peter Marks co-authored a piece in the Journal of the American Medical Association in December on the issue, writing that the bivalent boosters “likely only represents a temporizing measure until variants emerge that necessitate additional booster vaccination or modification of the current generation of vaccines.”

Options for a pan-coronavirus shot could be “protecting us against all alpha coronaviruses, or it could just be showing us the entire virus,” Gandhi said.

‘Not Out of the Woods’

As health professionals look ahead at the next phase of the nation’s Covid-19 response, they say it’s essential to make sure the general public is aware that the virus isn’t going away.

“In some ways, we’re still in an emergency, and there’s a lot of things that we don’t know around the disease, around long Covid, as well as what’s the best way to protect us,” Shen said.

Chatterjee said the public shouldn’t forget “there are still hundreds of people who are ending up in the hospital, in the ICU, and in the morgue who have died from this disease.”

“We are not out of the woods yet,” she said.

—With assistance from Jeannie Baumann.