Americans likely to need annual COVID-19 booster, officials say — but questions abound
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Experts raised questions about comments from U.S. officials this week that the new bivalent COVID-19 boosters are likely the first of what will become annual shots against SARS-CoV-2.
“We likely are moving toward a path with a vaccination cadence similar to that of the annual influenza vaccine, with annual, updated COVID-19 shots matched to the currently circulating strains for most of the population,” Anthony S. Fauci, MD, director of the National Institute of Allergy and Infectious Diseases, said during a White House briefing on Tuesday.
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President Joe Biden said in a statement that this week starts “a new phase in our COVID-19 response,” and the new approach means most Americans will receive “one COVID-19 shot, once a year, each fall.”
The comments that COVID-19 vaccination may be handled similarly to influenza vaccination followed the FDA’s authorization — and CDC’s recommendation — of the bivalent vaccines from Moderna and Pfizer-BioNTech last week, and the CDC putting a distribution plan into action in the days since.
There is concern, however, that similarities between SARS-CoV-2 and influenza have been overestimated as scientists have raced to keep up with the emergence of new variants and repeated waves of infection.
“I don’t think it’s possible to telegraph the behavior of SARS-CoV-2 at this point. There are some analogies of influenza, but they only hold to a certain extent,” Amesh A. Adalja, MD, senior scholar at the Johns Hopkins Center for Health Security, told Healio.
The newly authorized bivalent vaccines are akin to influenza vaccines in that they target circulating strains — in this case, the original strain of SARS-CoV-2 and the omicron BA.4 and BA.5 subvariants, which make up more than 99% of circulating SARS-CoV-2 viruses, according to CDC Director Rochelle P. Walensky, MD, MPH.
Fauci said the new boosters are meant to add to the “broad coverage” people got from the original vaccines, noting that the original vaccines have provided protection against some portion of nearly all variants of SARS-CoV-2 thus far, and he encouraged people to get their initial vaccinations if they have not already.
The updated boosters are expected to provide more protection against the circulating omicron strains, Fauci said, but cautioned that “it is difficult to predict at this point how much better that protection will be.” The shots were authorized and recommended based on positive preclinical data from mouse studies and research that studied other bivalent SARS-CoV-2 vaccines containing earlier omicron subvariants.
Kathryn M. Edwards, MD, scientific director at the Vanderbilt Vaccine Research Program, told Healio that there are not yet the data “to confirm that yearly booster vaccinations will do the trick. We will need to assess the vaccine effectiveness over the next months to ensure that this will be an effective approach.”
The major concern is the potential for another variant of concern (VOC) to emerge and how vaccines will handle the new challenge.
“What is critical is to have a system that can detect new VOCs, as well as measure the vaccine effectiveness of the vaccine in use at the time the new VOC appears to be taking over,” Walter A. Orenstein, MD, associate director at the Emory Vaccine Center and director of the Emory-UGA Center of Excellence for Influenza Research and Surveillance, told Healio.
The inability to predict VOCs and vaccine efficacy is a significant concern, according to David J. Diemert, MD, professor of medicine and of microbiology, immunology and tropical medicine at George Washington University.
“There’s one huge difference between COVID and the flu, and that’s that flu is purely seasonal,” Diemert told Healio. “So, we have time, breathing space, in order to formulate the next season’s components of the vaccine, whereas there’s been no break in COVID since it started, and we’ve had subsequent waves. ... I think it’s much more difficult to predict what will happen with COVID.”
The speed with which the virus has mutated while averting previous strain immunity makes it unclear “whether annual vaccinations will be too long, not long enough or just right,” Orenstein said.
The longer term goal, according to officials and others, is some type of universal coronavirus vaccine.
“We want to get to a pan-coronavirus type of vaccine with either a different platform or a better immunogen to do that,” Fauci said during Tuesday’s briefing, referring to what White House Coronavirus Response Coordinator Ashish K. Jha, MD, has called “variant-proof vaccines.”
Diemert said a universal vaccine is theoretical at this point but that scientists may find a part of the SARS-CoV-2 virus that does not change or mutate very quickly. This, he said, could protect against all variants as they appear. A universal vaccine has also been a longtime target of influenza vaccine researchers.
“Everything so far focuses on the spike protein [of SARS-CoV-2], which is what binds to us, but there’s other parts to the virus and it’s possible that by targeting those other parts it might be successful. But we don’t have any data to support that that’s going to be possible at this point,” Diemert said.
Calling it “partially luck” that a new VOC has not emerged while the bivalent vaccines were being developed, Diemert said that messenger RNA vaccines like the ones developed by Moderna and Pfizer-BioNTech have the best potential to be updated quickly, which is a benefit.
At the briefing, Jha focused on the fact that the bivalent vaccines “exactly” match the variants in circulation, and said if BA.5 continues to evolve, “this updated vaccine will continue to provide a very high degree of protection.”
“For the last 2 years, this virus has continued to evolve while our vaccines stayed the same. But now we have a vaccine that matches the dominant strain out there,” Jha said.
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