The updated COVID-19 boosters targeting the BA.4/5 subvariants now rolling out nationwide are meant to head off a surge of the disease this fall and winter—but they are also meant to signal a shift in the nation's pandemic response, which is moving out of an emergency phase to a place with routine, potentially annual vaccinations against a virus that is clearly not going away.

In a White House press briefing Tuesday, top infectious disease expert Anthony Fauci along with other Biden administration officials, repeatedly pushed the idea that this new phase will see COVID-19 vaccinations follow the footsteps of seasonal flu vaccines.

"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 towards 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," Fauci said.

He stressed that some people might need more frequent vaccinations, such as the elderly and those with compromised immune systems. But for younger, generally healthy Americans, annual shots appear to be the way forward. This follows efforts from the Food and Drug Administration, which has long aimed at coupling COVID boosters with flu shots this fall.

Curveballs

There is a significant caveat to this strategy, however. The annual booster plan is barring an "out-of-left-field" variant.

"It is a possibility we're going to get some crazy curveball," Fauci said. "We plan for what we think is the median, the most likely scenario. But we're always watching for that unusual event, and if that happens, we will address it, and we will adjust to it, and we’ll account for it," he said. "But I think the most likely scenario is we're going to see ongoing evolution off of BA.5," which is the currently dominant variant in the US and targeted by the new bivalent booster doses.

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White House COVID-19 Response Coordinator Ashish Jha echoed the points while also touting the utility of annual boosters that can be bundled with seasonal flu shots."Barring those variant curveballs, for a large majority of Americans, we are moving to a point where a single annual COVID shot should provide a high degree of protection against serious illness all year," Jha said. "That's an important milestone."

In advocating for Americans to get both shots this fall, he added: "I really believe this is why God gave us two arms—one for the flu shot and the other one for the COVID shot."

While the annual booster strategy is neat and tidy, the data backing up the strategy is still sketchy. The seasonality of SARS-CoV-2 and durability of future vaccines remain unclear. It's unknown if most Americans will need yearly shots going forward, despite the message from the White House on Tuesday. And long term, Jha and Fauci noted that a vaccine that could provide broader protection for longer is the ideal.

"We want to get a pan-coronavirus type of a vaccine with either a different platform or a better immunogen to do that, hopefully even with mucosally administrated," Fauci said. "But that's the long game."

Uptake

For now, the administration is banking on the idea that SARS-CoV-2 will continue to evolve along the lines of the current lineage, BA.5, which would require only modest annual vaccine updates, similar to what is done with the flu vaccines. The administration also hopes that tying the COVID boosters to seasonal flu shots will boost uptake and acceptance.

In the press briefing, Rochelle Walensky, director of the Centers for Disease Control and Prevention, noted that scientists were projecting the impact of COVID boosters based on how many Americans typically get annual flu vaccines.

"Modeling projections show that an uptake of updated COVID-19 vaccine doses similar to an annual flu vaccine coverage early this fall could prevent as many as 100,000 hospitalizations, 9,000 deaths and save billions of dollars in direct medical cost," Walenksy said.

But getting a similar number of Americans to get a COVID-19 booster as a flu vaccine may be a stretch. The percentage of Americans who get a seasonal flu shot has ranged from about 42 percent to 52 percent in recent years. So far, 67.5 percent of the US population has gotten their full primary series. But only half of those fully vaccinated have received a single booster. In other words, only about 33 percent of the US population is boosted. And only 34 percent of people age 50 and over who have gotten a first booster, and are eligible for a second, have gotten one.