Pfizer Inc (PFE.N) Chief Executive Officer Albert Bourla said on Monday he was unsure about the need for a fourth dose of COVID-19 vaccine and that a shot targeting the highly contagious Omicron variant would be ready in March.

The comments contrasted with those made by Moderna Inc (MRNA.O) CEO Stephen Bancel, who said last week people could need another shot in the fall of 2022 as the efficacy of boosters was likely to decline over the next few months.

A huge Omicron-driven spike in COVID-19 cases has forced some nations to look to another booster dose, but early signs suggest repeat vaccination may be a hard sell as beleaguered populations enter their third pandemic year.

“I don’t know if there is a need for a fourth booster, that is something that needs to be tested,” Bourla said on CNBC, ahead of Pfizer’s presentation at the J.P. Morgan healthcare conference.

Work is ongoing on a new version of COVID-19 vaccine that would be effective against Omicron and other variants, he said.

The U.S. drugmaker earlier in the day announced three deals to broaden the use of the messenger RNA technology (mRNA) that its COVID-19 vaccine was based on, including a pact worth as much as $1.35 billion with gene-editing specialist Beam Therapeutics (BEAM.O).

Pfizer has been looking to advance the development of mRNA-based vaccines and therapeutics after it led global efforts to develop a COVID-19 shot against the pandemic.

The company will also collaborate with Codex DNA Inc (DNAY.O) to leverage the biotech’s proprietary technology, which could enable more efficient development of mRNA-based vaccines, therapeutics and other biopharma products.

It deal with private biotech Acuitas Therapeutics will focus on the use of the Vancouver-based company’s lipid nanoparticle technology for developing up to ten vaccines or therapeutics.