The FDA Is Prepping for Fall Covid-19 Boosters. The Next Step Is Today.

Covid-19’s impact is at an ebb this spring, with the number of hospitalizations low and deaths declining. Vaccine makers, however, still plan to manufacture and sell tens of millions of doses in the U.S. this year.
Pfizer
(ticker: PFE) has told investors to expect Covid-19 vaccine revenue of around $13.5 billion this year, while
Moderna
(MRNA) says its Covid-19 vaccine revenue will be at least $5 billion.

As the meeting kicked off on Thursday morning, a Centers for Disease Control and Prevention official, Dr. Ruth Link-Gelles, laid out statistics on the real-world efficacy of last year’s bivalent boosters, intended to protect against both the original strain of the virus and the one that was circulating last fall. The numbers weren’t encouraging.

Efficacy of the bivalent shots against hospitalization dropped sharply over time, particularly in the period when variants in the XBB family became dominant in the U.S.. Efficacy against critical illness held up better.

One slide presented by Link-Gelles showed that protection against hospitalization for patients who received bivalent boosters dropped from 54% after around a month, to 6% after about four and a half months. When one panelist asked why hospitalization rates weren’t higher, given the relatively low levels of protection provided by the bootsers, Link-Gelles said that prior immunity from infections and earlier rounds of vaccination were also providing protection.

“I think our hospitals are probably staying less full because we do have such high levels of prior infection, prior monovalent vaccine,” Link-Gelles said. “The bivalent boosters are giving those folks added protection on top of that hybrid immunity.”

While the FDA recently authorized a second dose of last year’s bivalent boosters for adults over 65, a broader booster campaign is expected to launch in the fall. At Thursday’s meeting, the FDA’s vaccines advisors will discuss which strain of the virus that causes Covid-19 those fall boosters should target, in a similar process to how influenza vaccines are designed.

Here’s what to expect.

No More Bivalent Boosters

Last year, Moderna and Pfizer rolled out updated Covid-19 vaccines that targeted both the original strain of the virus and the Omicron subvariants known as BA.4 and BA.5. This year, it might no longer be necessary to include the original strain in the booster. Instead, FDA staff seemed to suggest in a briefing document released this week that they favor a monovalent booster targeting a variant within the Omicron subfamily known as XBB.

While boosters based on the original version of the virus can protect against severe disease, that protection is diminishing, FDA staff said, citing a discussion among health regulators from around the world at a conference in May.

“Based on the global dominance of the XBB descendant lineages, in conjunction with the high level of baseline immunity to the ancestral virus strain, regulators concluded that a monovalent XBB vaccine would be an adequate candidate for a Covid-19 vaccine composition update,” FDA staff wrote in the briefing document.

A May 18 statement from a World Health Organization working group also recommended a monovalent vaccine targeting a member of the XBB lineage. At the Thursday meeting, the FDA will ask members of its advisory committee to vote on whether to update the vaccines with a monovalent XBB-targeted vaccine.

Which XBB Subvariant?

The next question for the advisors will be which XBB subvariant the vaccines should target. The FDA won’t ask for a vote on this question, but rather a discussion among advisors.

According to the CDC, a variant called XBB.1.5 is currently dominant in the U.S., accounting for 39.9% of infections, followed by XBB.1.16 at 18.2%, and XBB.1.9.1 at 12.5%. FDA staff wrote in their briefing document that XBB.1.16 “could be dominant” by the fall, but that other variants could also be playing a significant role.

“Current sublineages under consideration include XBB.1.5, XBB.1.16, or XBB.2.3,” FDA staff wrote.

Will Anyone Take These Doses?

The question looming over the meeting is whether these vaccines will see any uptake. The number of Americans taking boosters dropped sharply as the pandemic proceeded: While 69.5% of the U.S. has completed the primary series of a Covid-19 vaccine, which rolled out in late 2020 and 2021, only 17% has received one of the updated boosters that arrived last year.

Thursday’s meeting could bring some debate around which populations actually need updated boosters this fall. Analysts expect Covid-19 vaccine sales to continue to fall. The FactSet analyst consensus estimate for Moderna’s Covid-19 vaccine sales is $6.6 billion this year and $5.7 billion next year.

Write to Josh Nathan-Kazis at [email protected]