The head of the Pfizer pharmaceutical company has warned that people will probably need a third dose of his laboratory’s Covid-19 shot within six to 12 months of vaccination, adding that annual booster shots may also be required. The Pfizer chief has defended the relatively higher cost of the treatment. Speaking in an interview on American television, Pfizer CEO, Albert Bourla, said that his company was currently evaluating long-term vaccination needs, but that a third dose and annual revaccination were a “likely scenario”. “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 CBC. The whole situation 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. Researchers currently don’t know for how long vaccines will provide protection against the coronavirus. Pfizer published a study earlier this month claiming that its jab is more than 91 percent effective at protecting against the coronavirus, and more than 95 percent effective against severe cases of Covid-19 for 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, warned 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,” he 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” that, he said. “I think for planning purposes, planning purposes only, I think we should expect that we may have to boost.” Bourla also on Thursday defended the price of his company’s vaccine, saying the product is saving lives and will not be sold to poor countries for a profit. “Vaccines are very expensive,” Bourla said in an interview with several European news outlets. “They save human lives, they allow economies to reopen, but we sell them at the price of a meal,” he was quoted as saying.