The chief executive of Pfizer said people will probably need a third dose of his company’s Covid-19 vaccine within a year of being fully vaccinated.
Albert Bourla also said annual vaccinations against the coronavirus may be required.
"We need to see what would be the sequence and for how often we need to do that, that remains to be seen," Mr Bourla told CNBC.
"A likely scenario is that there will be a need for a third dose, somewhere between six and 12 months, and then from there there will be an annual revaccination, but all of that needs to be confirmed," he said. Variants will play a "key role", he said.
The interview was recorded on April 1.
“It is extremely important to suppress the pool of people that can be susceptible to the virus,” Mr Bourla said.
Researchers do not know how long vaccines provide protection against the coronavirus.
Pfizer published a study this month that said its vaccine, developed in partnership with German company BioNTech, was more than 91 per cent effective at protecting against the coronavirus, and more than 95 per cent effective against severe cases of Covid-19, up to six months after the second dose.
But researchers say more data is needed to determine whether protection lasts beyond six months.
David Kessler, the head of US President Joe Biden's Covid-19 response team, told a congressional committee on Thursday that Americans should expect to receive booster shots to defend against coronavirus variants.
“We don’t know everything at this moment,” Dr Kessler told the House coronavirus crisis subcommittee. “We are studying the durability of the antibody response.
"It seems strong but there is some waning of that and no doubt the variants challenge. For planning purposes only, I think we should expect that we may have to boost."
The Pfizer-BioNTech vaccine plays a leading role in American and European vaccination campaigns.
The pharmaceutical giant announced in February that it was testing a third dose of its vaccine to better battle emerging variants.
