Dr. Anthony Fauci says it's conceivable that people may need to get Covid vaccine booster shots every year or two, but what variant the vaccine would target remains an open question.
In an ideal world, however, scientists hope to develop a shot that would protect against all future variants of the coronavirus, as well as other types of coronaviruses that cause other diseases, Fauci, the director of the National Institute of Allergy and Infectious Diseases, told NBC News.
Keeping up with the evolution of the coronavirus has felt a little like playing viral whack-a-mole: Every time a new variant pops up, there's a scramble to find out whether our current vaccines can smack it down.
So far, it appears that the vaccines are working to prevent severe illness and death even from the omicron variant, although waning immunity has led to the need for boosters.
"We were doing quite well with a primary vaccination and a boost with delta. Then all of a sudden omicron came along," Fauci said. "And if you look at the efficacy against the delta versus omicron, it went down to around 30 percent."
Still, he said, the U.S. has lucked out with the vaccines' original formula.
"We're lucky that we made the vaccine against the original ancestral strain," he said. "And then as the variants came along, we were fortunate that even though they were different, they were not so different that the vaccine didn't cover it well."
Even though the CEO of Moderna has said we'll need boosters possibly by the fall, and Pfizer-BioNTech is about to start testing an omicron-specific booster, Fauci said it's too soon to know what is warranted.
"We've only recently boosted people. We will find out if the booster gives you a degree of durability of protection and actually should be the standard regimen of three doses of an mRNA and two doses of J&J," he said. "Or — and it's a big 'or' right now — will we need to boost people every year or so?"
While Israel recently began administering fourth doses to certain at-risk groups, there is some concern among vaccine experts that too many boosters could affect the immune system in a way that could weaken the effectiveness of future shots.
"While use of additional boosters can be part of contingency plans, repeated vaccinations within short intervals would not represent a sustainable long-term strategy," Marco Cavaleri, the head of vaccines strategy for the European Medicines Agency, said at a media briefing Tuesday.
Cavaleri added that it is important to "try to come up with an approach that will be suitable in order to prevent a future variant."
Fauci is pushing for a vaccine that "would mean that the initial vaccination would cover all of these little variants, so you wouldn't have to worry" that protection would rise and fall or that repeated boosters would be needed.
The end game
Fauci is looking even further into the future, to a vaccine that protects against all coronaviruses, not just the one that causes Covid-19.
That includes other coronaviruses that have led to severe illness and death, such as the original SARS virus that caused an outbreak in 2003, and the MERS virus, which has killed more than 800 people in the last decade — most of them in the Middle East.
"We want a pan-coronavirus vaccine so that you have it on the shelf to respond to the next viral pandemic," Fauci said. "Ultimately, you want to get a vaccine that covers everything."
It is likely to be years before development of a so-called pan-coronavirus vaccine is far enough along even for clinical trials. The vaccines for SARS-CoV-2 were developed so quickly in 2020, Fauci said, because the scientific community had decades of fundamental basic research to "hit the ground running" once the original strain was sequenced.
Historically, scientists have been largely unsuccessful with universal viral vaccines. Work on a universal flu vaccine, for example, has been going on for years.
The problem is that many viruses have multiple strains that cause severe illness.
"The reason we can't get an HIV vaccine," said Dr. Paul Goepfert, the director of the Alabama Vaccine Research Clinic at the University of Alabama at Birmingham, "is because there's 10,000 different types of strains of HIV" that cause AIDS.
"If there was only one strain of HIV, we would have had our vaccine many, many years ago," Goepfert said.
Developing a vaccine to cover every single section of the extensive coronavirus family tree would require a massive scientific undertaking — not entirely unlike trying to keep everyone at a huge family reunion focused on the same activity.
The end game in this case would be to render all forms of a virus powerless when they inevitably mutate — or at least take them from something that could kill you to something that causes only a minor cold.
"When you're dealing with respiratory infections, the fundamental goal is to make sure people don't get seriously ill," Fauci said. "We can deal with sniffles for a day or two. We don't want people to die."