When President Joe Biden rolled up his sleeve to get the updated COVID-19 booster in October, he pledged that the majority of Americans would only need one coronavirus shot a year.
For most Americans, one COVID shot each year will be all they need,” Biden said at the White House. “And if you get it, you’ll be protected. And if you don’t, you’re putting yourself and other people at unnecessary risk.
He has also spread the idea on Twitter, saying: “Our nation’s experts say that most folks will only need one updated COVID vaccine to stay protected all year long. One shot, once a year. Just like flu.”
Several of Biden’s top health officials have echoed the message.
“It is becoming increasingly clear that looking forward with the COVID-19 pandemic, in the absence of a dramatically different variant, 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,” leading infectious disease expert Anthony Fauci said in September.
But more than three months after the Biden administration first floated the idea of an annual COVID-19 booster shot, no official policy has been announced as questions and hurdles remain.
For one, the ever-changing pool of COVID-19 variants makes it difficult to formulate a shot that exactly matches what is circulating – a similar challenge faced by the flu vaccine every season. The updated bivalent shots were designed to take on omicron subvariants BA.4 and BA.5 as well as the original coronavirus strain. Since the shots rolled out at the end of August, the variant scene has – not surprisingly – changed.
August, BA.5 was the dominant strain circulating, but now, XBB.1.5 leads the variant pack causing over 40% of COVID-19 infections in the U.S. last week, according to estimates from the Centers for Disease Control and Prevention. It’s been called the “most transmissible subvariant that has been detected yet,” and it’s unclear how well the updated booster shot will stand up to it.
That means that while public health officials believe the updated boosters will still provide increased protection against severe disease, hospitalization, and death from XBB.1.5, the shots aren’t a perfect match to the omicron subvariants that are driving the majority of infections.
It’s a humbling reminder of how fast the variant scene can change. One of the biggest caveats to shifting to an annual COVID-19 booster cycle is that a new variant can pop up at any time, which is a limiting factor the Biden administration has acknowledged.
“The wild card of a way-out, out-of-left-field variant coming, if that happens, all bets are off and we change,” Fauci said of the annual booster idea.
But variants aren’t the only issue for such a strategy. The Biden administration would also need to decide what time of year to offer the shot, which could be trickier than it sounds.
Administration officials have compared the COVID-19 booster campaign to the flu shot, which is recommended in the fall to maximize protection during the winter when the flu season typically surges.
The coronavirus, however, has yet to become seasonal, with surges happening in the summer, fall, and winter.
“We know that the vaccine is protective, but you want to have that right before there’s a lot of transmission in your community because it’s most effective soon after it’s administered,” says Keri Althoff, an epidemiologist at the Johns Hopkins Bloomberg School of Public Health.
The problem is that the antibodies produced by the COVID-19 shots wane over time, with previous studies reporting a notable decline within the first three months. But the situation is different from person to person, and protection against serious illness tends to outlast protection against infection.
“When we talk about waning antibodies, we have to remember that this is not a switch,” Althoff says. “It doesn’t mean that after six months, all of a sudden, you have no protection left from a vaccine.”
Additionally, experts agree that offering a booster shot every three to four months as antibodies from the previous shot diminish is not the answer.
“Are we going to be in a situation where we’d recommend a vaccine every three or four months just because antibodies are waning?” No, Althoff says, “but we are likely going to be in a situation where if we see an annual vaccine for COVID, we will want to think through the timing of that to ensure the greatest protection conveyed during the times we anticipate the highest levels of transmission in our communities.
These questions are exactly what a committee of vaccine experts will be discussing at an upcoming Food and Drug Administration meeting in late January. Among other things, they will talk about “how and whether the composition and schedule for booster doses should be adjusted moving forward.”
“Since the initial authorizations of these vaccines, we have learned that protection wanes over time, especially as the virus rapidly mutates and new variants and subvariants emerge,” FDA’s Peter Marks said in a statement announcing the meeting on Jan. 26. “Therefore, it’s important to continue discussions about the optimal composition of COVID-19 vaccines for primary and booster vaccination, as well as the optimal interval for booster vaccination.”