Booster shots may not be medically necessary for another one to five years, disease experts wager.
But pharmaceutical companies are prepping to distribute boosters to the US before the end of 2021.
In either case, boosters probably won't require the same urgency as initial vaccines do.
The next vaccine race is underway - this time for booster shots.
Leading vaccine developers, including Pfizer, Moderna, and Novavax, are sizing up the market for boosters - an additional jab to boost protection for those already vaccinated against COVID-19. These drug companies have also crafted new versions of their shots, customized to fight some of the most concerning variants the world has seen.
Meanwhile, researchers are still waiting to find out how long initial vaccine protection lasts. That's creating a contentious split in the range of predictions about when we may need more shots. Figuring out when to boost is one of the biggest lingering mysteries of the pandemic in the US, and a growing disconnect between drug companies and scientists could make it all the more complicated to find consensus.
The CEOs of leading pharmaceutical companies have become forceful advocates for administering boosters sooner rather than later - potentially as early as later this year. Theirs is essentially a "better safe than sorry" mentality, one that happens to align neatly with a chance for their companies to earn additional billions in revenue.
"I think for next fall, we, as a community, should rather be two months too early boosting than two months too late," Moderna CEO Stéphane Bancel said at a Goldman Sachs investor conference last week.
Yet physicians and infectious-disease experts are increasingly finding themselves on the other side of the debate, voicing hope that boosters may not be necessary for several years.
Insider spoke with nine leading experts, who took their best guesses about how long vaccine protection may last. Those predictions were quite a bit longer than what pharmaceutical companies suggest: Some experts said boosters probably won't be necessary for another one to five years, while others questioned whether the general public will ever need another round of shots.
COVID-19 vaccine protection is shaping up to be pretty darn good
Research so far indicates that vaccine protection against the coronavirus lasts for the better part of a year - and likely many months beyond that.
Pfizer has said its vaccine is 91.3% effective against COVID-19 any time between one week and six months after a second dose. Moderna's clinical trials, meanwhile, demonstrated that vaccine recipients still have antibodies at least six months after their second dose (according to a small study of 33 participants).
Despite prior fears, COVID-19 vaccines are also proving effective in the face of variants. Although some of the more concerning strains may not elicit the same level of antibody response in vaccinated people, other aspects of vaccine protection seem to remain intact.
"We can give away a little protection with the variants, even if it's 10-fold less or 100-fold less," said Dr. Arnold Monto, an epidemiologist at the University of Michigan. "The studies that have been done show the reduction in actual efficacy is minimal."
After all, no vaccine has ever been 100% effective in the real world. That's not the goal.
"If the duration of protection is such that you can still get a mild cold, but you don't end up in the hospital, the vaccine will still be a success," Dr. Larry Corey, a virologist at Fred Hutchinson Cancer Research Center, said.
Early studies also suggest that the mRNA shots from Pfizer and Moderna offer more robust protection than natural immunity from an infection.
"Vaccines, actually, at least with regard to SARS-CoV-2, can do better than nature," Dr. Anthony Fauci, the US's leading infectious-disease expert, said in May.
He was citing a set of laboratory studies, which found that vaccines are better at combating variants than a prior infection alone, and that people who got vaccinated after getting COVID-19 may have the strongest immune responses of all.
Boosters might be necessary in 1 to 5 years - but perhaps never
Disease researchers are thus far hesitant to suggest a timeframe in which booster shots will be necessary.
"Should boosters occur in a year, or 2022, or 2023, or 2024? I can honestly say I don't know what the best answer is at the moment," Corey said.
The coronavirus-watchers at the Centers for Disease Control and Prevention, who will advise the federal government on when to recommend boosters, don't have an answer, either.
"I think this is so different from what we have seen with other diseases and other vaccines that it's really difficult to say," Dr. Jennifer Verani, co-lead of the CDC vaccine effectiveness team, said.
"Our team is really focused on generating the data that will be needed to inform those decisions," she added. "I really don't think we can speculate at this point what the recommendations will be with regards to a booster."
Some of that data will come from the same large clinical trials that helped show these vaccines work in the first place. Those studies are still ongoing, with plans to follow up with volunteers over the course of about two years, monitoring them for signs of illness and routinely testing their blood.
Once those first vaccinated groups start to get more breakthrough infections - cases of COVID-19 diagnosed at least two weeks after someone is fully vaccinated - that will be a sign vaccine protection is waning and boosters are needed.
Federal regulators in the US are watching closely for that signal.
"If I had to look at my crystal ball, it's probably not sooner, hopefully, than a year after being vaccinated, for the average adult," Dr. Peter Marks, director of the Food and Drug Administration's biologics center, said during a recent webinar.
Other experts think protection may last far longer. Dr. Paul Offit, director of the Vaccine Education Center at Children's Hospital of Philadelphia, estimates it could be three to five years.
"I would predict that protection will last for a few years - protection as I define it, which is protection against severe to critical disease," Offit told Insider last month.
But it's also possible that booster protection won't be necessary for everyone. A follow-up shot may be recommended just for elderly and immunocompromised people, for example, or for people who never caught the disease.
"We're going to have to be guided by the epidemiology and what happens with the virus - and, like we've had to do for the last year, we're going to have to continue to adapt based on what happens," Dr. Robert Atmar, an infectious-disease expert from Baylor Vaccine Research Center, said.
At the very least, experts don't think we'll witness more scenes of people camping out at their local pharmacy for boosters, as some did at the beginning of the current rollout. That's because vaccine protection won't plummet to zero overnight, and trials will likely be able to send up an early flare when participants' immunity starts to wane.
Pharmaceutical companies are planning for a bullish fall-winter booster campaign
Pfizer CEO Albert Bourla estimated in April that people would likely need booster shots within 12 months of getting fully vaccinated. That'd be as early as December for some in the US.
But disease experts are largely skeptical of that rapid timeline.
"Corporate CEOs have agendas, which is to get more of their vaccines into arms," John Moore, a vaccine expert at Cornell University, said. "So I tune out what CEOs say."
It's also possible that only certain vaccines may require boosters but not others. Johnson & Johnson's adenovirus shot, for instance, is less effective at reducing mild and moderate infections than Pfizer's and Moderna's mRNA shots, so immunity from that vaccine may not last as long.
Moore said J&J's shot "was pushed out as a one-dose vaccine, when it's really, to my mind, a two dose vaccine." Because of that, he thinks it's possible that "it may be converted to a two-dose vaccine later this year."
Other experts are investigating whether mixing and matching vaccines - administering a booster that uses a different vaccine platform than the first shot a person got - could offer extra protection. Atmar is leading one such study, which may provide preliminary results this fall.
"Will boosting with an mRNA vaccine, or just boosting with any vaccine, bring the J&J up to the mRNA-based vaccines?" he said. "We don't really have the answer to that."
'It's not a falling-off-a-cliff thing'
Assuming vaccine efficacy does at some point start to slip, countries' decisions about when to roll out boosters will depend on the level of vaccine efficacy they're willing to accept.
"If Pfizer's follow-up trial shows that in two years, vaccine efficacy dropped to 60%, then Israel may consider a booster," Eyal Leshem, an infectious-disease specialist at Sheba Medical Center, Israel's largest hospital, said.
But countries probably won't have to rush that decision.
"It's not a falling-off-a-cliff thing," Moore said. "It's a very gradual process. So at some point it might be thought that antibody responses have dropped too far, on a population basis."
Even then, though, antibody responses might only dip in certain groups of people, such as the elderly or patients with preexisting health conditions.
"It may be a population-specific booster," Leshem said. "It may be discovered, for example, that persons over a certain age - say, over 65 or over 80 - have a waning of immunity that's faster, and this population is going to get a booster recommendation."
It's also possible that vaccinated people may only need a low-dose booster - smaller than their original - which would also likely mean milder side effects.
"We might be able to reduce the dose and extend the supplies," Monto said, adding, "If you look at the immunogenicity, you're pretty good even with half a dose."
In the US, anyone who does eventually need a booster will likely get it for free, according to David Kessler, chief science officer of the White House COVID-19 response team.
But of course, any decisions about boosters must also factor in disparate vaccination rates around the world. As of now, less than 10% of the world has been fully vaccinated, and infectious-disease experts agree that the virus poses the greatest threat to everyone when it can spread and mutate among large, unvaccinated groups.
"Let's hope we don't need a booster shot in the first world before the rest of the world is vaccinated," Monto said.
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