When the first COVID-19 vaccines arrived nearly two years ago, they came with the promise that their formulas could be adjusted quickly and easily to target coronavirus variants and allow for a nimble defense to an evolving pathogen.
Now that promise is being put to the test.
Millions of Americans 12 and older are newly eligible to get redesigned booster shots authorized last week by federal officials. The new products — called “bivalent” vaccines, because they address two strains of the virus — target both the ancestral coronavirus that launched the pandemic as well as currently circulating omicron subvariants.
For many Americans who have already gotten at least one booster shot, an additional dose may feel a bit ho-hum. But these new shots mark a milestone in the pandemic: the first time that mRNA vaccines — the most widely used type in the U.S. — have been tweaked to match a variant in as close to real time as possible.
The boosters will be administered in a manner typically reserved for the annual flu shot, which is revamped each summer to match the expected influenza strain circulating in the fall and winter — though it’s too soon to say for sure whether COVID will develop a similar seasonal pattern.
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As the nation launches a fall COVID vaccination campaign to get Americans boosted ahead of another possible fall/winter surge, the revised shots will be under the spotlight, both for how well they hold up against the virus and how much appetite a pandemic-wary public has for yet another injection.
“There’s tremendous promise in this to further diminish the impact of the pandemic in our community and protect our residents, especially coming into the fall,” said Dr. Matt Willis, public health officer for Marin County. “This will be the largest number of people simultaneously eligible for the vaccine since the start of the pandemic.”
Whether the new boosters will prevent, or significantly weaken, a surge that could lead to tens of thousands more deaths and hospitalizations remains to be seen. It largely depends on how many people — especially those at high risk of severe illness — get the shots, as well as whether new variants arrive in the coming months that are able to slip by the updated vaccines.
It’s also not yet clear how well the reformulated shots will work against the strains they were designed to target. Experts are confident that they’ll buttress protection against severe illness and death, but they can’t say how well the new shots will work at preventing transmission and thus curtailing the spread of sickness.
“My feeling is that the omicron subvariants will continue for a little while longer, and if that remains true through the fall and winter, these new vaccines will definitely be useful,” said Dr. Lee Riley, an infectious disease expert at UC Berkeley. “But I think it’s mostly going to be about protecting against severe disease. Maybe if we get it to as many people as we can we can blunt transmission too.”
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The two vaccines — made by pharmaceutical giants Moderna and Pfizer — were able to be revised fairly quickly because their underlying mRNA technology allows for a relatively simple swap, or addition, of viral genetic material. For the bivalent, scientists also added fragments from the BA.4 and BA.5 subvariants, which are genetically very similar to each other.
Federal officials authorized and recommended the new vaccines with limited data on their effectiveness because of time constraints. Both Moderna and Pfizer have started human trials, but results won’t be available for another couple of months; waiting would have meant a potentially deadly delay for vulnerable Americans, federal authorities said.
Instead, officials based their decisions mostly on the results of animal studies, which suggest the bivalent boosters lead to higher levels of neutralizing antibodies compared to the original vaccine. Small human trials that tested a vaccine reformulated to match the first omicron variant, BA.1, also factored into their decisions.
“What’s good about the boosters was the adjustments were made very quickly by Moderna and Pfizer from the time, a couple months ago, that the (Food and Drug Administration) asked them to adjust and account for BA.4/5,” said San Francisco Health Officer Dr. Susan Philip. “The speed also means we don’t have great information in humans about how they work to prevent transmission or prevent acquiring infection.”
The timing of the bivalent boosters presents challenges. By now, nearly three years into the pandemic, many people — especially those who have been fully vaccinated and boosted — have returned to their pre-pandemic lives, and experts worry that they may see little need for additional vaccinations or precautions.
The proportion of eligible people who are getting boosters — two boosters have been recommended for those 50 and older — is getting smaller with each subsequent shot, and many experts predict uptake will be even lower this round. The Centers for Disease Control and Prevention released poll results last week that suggested 72% of Americans might get an updated shot, but many experts were skeptical uptake would be anywhere near that high.
“An awful lot of people are over COVID,” said Dr. John Swartzberg, an infectious disease doctor and professor emeritus at UC Berkeley School of Public Health. “Less than half of the population over 65 is up to date with their boosters. Clearly there’s booster fatigue, vaccine fatigue, and I suspect we’re going to see the same thing with this new one.”
In the United States, just 34% of people 50 and older have gotten their second booster — markedly lower than the 64% of people in the age group who’ve gotten their first, according to the CDC.
Those rates are higher in the Bay Area. Still, even here, less than half of eligible residents 50 and older have gotten their second booster, according to data from Bay Area counties that report the figures. A significantly higher proportion, 70% or higher of this population, got their first.
Public health officials may need to reframe the conversation around the new shots — perhaps ditching the term “booster” altogether and instead talking about them in the context of routine health care, said Dr. Kevin Schulman, a professor of medicine and health policy researcher at Stanford.
“What we’re not seeing is the marketing campaign to get this out there,” he said. “People are tired about it, no one wants to hear about another booster. How do we get messaging out there that gets us out of the vaccine-booster debate and makes this part of your routine preventive health?”
Dr. Eric Topol, executive vice president of Scripps Research in La Jolla (San Diego County), said he was disappointed the new vaccines were authorized without human results, and he worries that paucity of data will lead many people to question the shots. Topol himself plans to wait to get his next booster until clinical trial results are available in another couple of months.
Still, he said he expects the shots will prove effective, at least at providing protection against severe illness. “And if we don’t get the booster rate up — whatever that booster is — we’re going to have more and more people who have waned from their third or fourth shot,” Topol said. “We’re going to see problems.”
Topol said that however this latest booster campaign plays out, the challenges around updating the vaccines and getting them approved and out to the public should underscore the need for better, more durable products. He and other health experts have long argued that the country needs to invest in vaccines that would protect against all coronavirus variants and offer more lasting protection.
“My plea since January 2021 has been to develop a pan-virus vaccine because we can’t keep chasing variants,” he said. “We keep working with the original, tweaking it, and it’s probably not ever going to be good enough to give us maximal protection.”
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