Pfizer CEO Albert Bourla said that it is highly likely that people will require a third vaccine shot within 12 months of being fully vaccinated. Bourla said it is possible people will need to get vaccinated against the coronavirus annually. “We need to see what would be the sequence, and for how often we need to do that, that remains to be seen,” Bourla told CNBC in an interview recorded on April 1. “A likely scenario is that there will be likely 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, adding that variants will play a “key role.” “It is extremely important to suppress the pool of people that can be susceptible to the virus,” he said. At present, the researchers are not aware of how long the vaccine gives protection. Pfizer said earlier this month that its Covid-19 vaccine was more than 91% effective at protecting against the coronavirus and more than 95% effective against severe disease up to six months after the second dose. Moderna’s vaccine, which uses technology similar to Pfizer’s, was also shown to be highly effective at six months. Pfizer’s data was based on more than 12,000 vaccinated participants. However, researchers say more data is still needed to determine whether protection lasts after six months. “It seems strong but there is some waning of that and no doubt the variants challenge,” he said. “I think for planning purposes, planning purposes only, I think we should expect that we may have to boost.” The Pfizer vaccine, developed in partnership with German firm BioNTech, currently 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 combat the emerging variants.