Pfizer and BioNTech said Thursday that trials suggest that their vaccine is effective against a coronavirus variant that first emerged in South Africa, which some experts worry might evade existing shots.
The drugmakers also said in a statement that 12,000 people involved in their Phase 3 trial experienced high levels of protection against Covid-19 six months after their second doses, with no serious safety concerns.
"It is an important step to further confirm the strong efficacy and good safety data we have seen so far," said Uğur Şahin, CEO and co-founder of BioNTech.
"These data also provide the first clinical results that a vaccine can effectively protect against currently circulating variants, a critical factor to reach herd immunity and end this pandemic for the global population," he said.
The vaccine, developed by the American pharmaceutical giant Pfizer and its German partner, BioNTech, received emergency use authorization in December from the Food and Drug Administration, which is granted only in special circumstances.
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Thursday's trial results will allow the drugmakers to submit a full Biologics License Application to the FDA, Pfizer Chairman and CEO Albert Bourla said in the statement. They also plan to share the results with regulators around the world and to submit the data for peer review.
The study included 44,000 people, some of whom were given the vaccine and some a placebo. There were 927 symptomatic cases of Covid-19, only 77 of which were in those who were given the vaccine — a 91.3 percent degree of efficacy, according to the statement, which was issued in a non-peer-reviewed news release.
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Only one of 21 subjects with severe cases had been given the vaccine — indicating 95.3 percent efficacy, the statement said, using the FDA's definition of severity.
Going by the Centers for Disease Control and Prevention's definition, there were no severe cases in the vaccinated group, indicating 100 percent efficacy against severe disease, it said.
The CDC reported Monday that both the Pfizer and the Moderna vaccines are extremely effective in the real world, reducing infections by 90 percent in fully vaccinated people.
The findings, the first real-world data from the United States, are in line with similar research from other countries.
The Pfizer-BioNTech vaccine has been administered more than 76 million times in the U.S., more than Moderna's 69 million and Johnson & Johnson's 3 million, according to the CDC.
Part of the trial took place in South Africa, where the variant, known as B.1.351, first emerged. Some scientists worry that it might be able to escape existing vaccines.
There have been 312 identified cases of the strain in the U.S., according to the latest figures from the CDC.
In the Pfizer-BioNTech trial, six cases of the variant were observed, none of them in people who had been given the vaccine — indicating an efficacy of 100 percent, it said.
The drugmakers welcomed the news, because in February they said a laboratory test had suggested that their vaccine produced lower levels of antibodies against the strain.
Although the antibody levels were lower, "it does not appear to affect the high observed efficacy against this variant," the statement said Thursday.
The companies said Wednesday that their vaccine is safe and effective in teenagers ages 12 to 15. They plan to request emergency use authorization for those ages in the coming weeks.
Pfizer is also studying how well the vaccine works in children ages 6 months to 11 years. The first doses in that trial were administered last week.