(Bloomberg) -- Americans will get a clearer idea of how often they’ll roll up their sleeves for Covid-19 shots when advisers to US regulators meet Thursday to discuss an immunization schedule that looks more like the one used for flu.

The plan would have health officials meet each June to review which strains of the virus should be included in Covid shots to be deployed no later than September of the same year, according to documents released by the US Food and Drug Administration ahead of the Jan. 26 meeting. Moderna Inc. and the partnership of Pfizer Inc. and BioNTech SE are the biggest makers of doses for the US. 

Experts from around the world convene annually to make predictions about which flu strains will dominate during the upcoming season and should be targeted by shots. The FDA is looking for a similar coordinated effort to take place at least as often for Covid shots, one of several moves the agency hopes might help simplify the immunization process and encourage more Americans to stay up to date. 

Waning immunity from vaccinations and the emergence of new variants every few months has led regulators to recommend variant-targeted boosters, a tactic that so far has been unpopular among Americans and has even split some health experts on costs and benefits. Just weeks after rolling out the updated BA.4 and BA.5 boosters in September, new mutations were rampant. Now, even as the US sees the rise of an immune-evasive variant called XBB.1.5, booster uptake is hovering at about 15%.

Read more: What to Know about XBB and Other Omicron Subvariants

“We are working on potential updates against multiple strains, including XBB.1.5, and will be ready to deliver if an update is requested by regulators,” Moderna spokesperson Christopher Ridley said in an email. Pfizer didn’t immediately respond to a request for comment.

Moderna’s stock was up 1.9% as of 11:27 a.m. in New York, while Pfizer’s gained 0.3%. 

“Although the use of the bivalent mRNA boosters is supported by the available evidence, their deployment has been associated with significant implementation complexities,” the FDA said. Switching to one composition for both primary shots and boosters will help streamline the process, according to the agency documents.

Evidence suggests that immunity from prior exposure to the virus along with vaccination will provide enough protection so that most people will need one annual Covid booster, according to the documents. However, young children who might not have been previously exposed and people who are at higher risk for severe disease may need two yearly shots, the FDA said.

“An annual vaccine would be ideal because people would remember, they can do it with other vaccinations like flu and it can last,” Albert Bourla, chief executive officer of Covid vaccine-maker Pfizer Inc., said Jan. 18 in an interview with Bloomberg. 

Read more: Drugmakers Hunt for One Vaccine to Target All Covid Variants

The FDA is still concerned about evasion of vaccine-induced immunity by mutants of the fast-spreading omicron strain, according to the documents. That warrants continued surveillance of variants and also monitoring of the protection previous vaccines provide against new strains.

Pfizer and Moderna Inc. are both working on next-generation vaccines that hold up against mutations and provide longer-lasting protection, but it’s unlikely those will be ready to go into arms anytime soon.

--With assistance from Robert Langreth.

(Updates with company comment starting in fourth paragraph)

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