People who have received the Pfizer vaccine will "probably" need a third dose within six months to a year, and then an injection every year, said the chief executive of the drug company, Albert Bourla, speaking to CNBC.
"A probable hypothesis is that a third dose is needed, between six and 12 months later, and from then on it will be necessary to re-vaccinate every year, but all that has to be confirmed," he said. "Variants will play fundamental role," he added.
"It is extremely important to minimise the number of people vulnerable to the virus," continued Bourla.
The Pfizer / BioNTech alliance announced in February that it was studying the effects of a third dose of its vaccine in a clinical study.
This vaccine, like Moderna's, uses innovative messenger RNA technology, which has never been used before in real life.
Right now, these two vaccines are the ones that work the best, as the Pfizer / BioNTech vaccine shows 95 per cent efficacy against Covid-19 and Moderna 94.1 per cent, according to clinical studies.