(Bloomberg) -- Sanofi offered a strikingly low projection of the future need for Covid shots, saying boosters will be required only once every three to five years.

By 2024, the market for Covid shots will probably max out at around 500 million doses a year, with people’s immunity becoming more durable and the virus evolving, Thomas Triomphe, head of the French drugmaker’s vaccines unit, said at an investor event Wednesday.

“It’s very difficult to predict what it’s going to be a couple years down the road,” Triomphe said. “I suspect it’s going to be very low. But again, it’s a crystal-ball play.”

Ordinarily a leader in vaccines, Sanofi missed the boat on first-generation Covid shots. The product from Pfizer Inc. and its partner BioNTech SE has been particularly in demand. Pfizer recently projected $36 billion in sales for it this year. 

The early mRNA shots cause too many side effects, and societies will soon demand products that are better tolerated, Bill Averbeck, Sanofi’s head of influenza franchise, said at the event.

Sanofi expects to release late-stage trial results for its own Covid vaccine candidate -- which relies on recombinant protein technology used in its flu shots -- by the end of this year. It will also release data about its efficacy as a universal booster, and early results of that research are “very encouraging,” Chief Executive Officer Paul Hudson said Wednesday.

Sanofi is partnered with GlaxoSmithKline Plc on that product, with the latter providing an adjuvant designed to enhance the immune response. The companies have commitments from European Union countries for 75 million doses, along with a partnership with the U.S. government, which helped pay for development, Triomphe said.

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