A final analysis of the Phase 3 trial of Pfizer’s coronavirus vaccine shows it was 95% effective in preventing infections, even in older adults, and caused no serious safety concerns, the company said Wednesday.
The company counted 170 cases of coronavirus infection among volunteers who took part in the trial. It said 162 infections were in people who got placebo, or plain saline shots, while eight cases were in participants who got the actual vaccine. That works out to an efficacy of 95%, Pfizer said.
The data show Pfizer’s initial claim of a better than 90% efficacy — a claim that stunned and pleased health officials and vaccine developers last week — holds up.
“Efficacy was consistent across age, race and ethnicity demographics. The observed efficacy in adults over 65 years of age was over 94%,” Pfizer and its German partner BioNTech said in a joint statement.
“There were 10 severe cases of Covid-19 observed in the trial, with nine of the cases occurring in the placebo group and one in the BNT162b2 vaccinated group.” BNT162b2 is the experimental name for the vaccine.
An independent group has been keeping an eye on results and side-effects. “To date, the Data Monitoring Committee for the study has not reported any serious safety concerns related to the vaccine,” the companies said.
“The only Grade 3 (severe) solicited adverse event greater than or equal to 2% in frequency after the first or second dose was fatigue at 3.7% following dose 2,” the companies said. Older adults tended to have fewer adverse events and those they had were milder.
Pfizer said it will seek US Food and Drug Administration emergency use authorization “within days.”
“These data also will be submitted to other regulatory agencies around the world,” Pfizer said. They plan to publish the data in a peer-reviewed scientific journal, as well.
“The rapid protection this vaccine provides — combined with its tolerability profile in all age groups studied so far — should help make this vaccine an important tool to address the current pandemic,” said Dr. Ugur Sahin, CEO and co-founder of BioNTech.
Pfizer said on November 9 that interim data provided initial evidence the vaccine had an efficacy of more than 90%. That data was based on the first 94 cases of coronavirus infection among volunteers. The company said at the time it would need to count more cases of infection in the trial before it could consider the Phase 3 part of the trial finished and seek FDA authorization.
The Phase 3 clinical trial of the vaccine began on July 27. Pfizer said of 43,661 volunteers enrolled, 41,135 have received a second dose of the vaccine or placebo. The FDA said it wanted at least two months of safety tracking on volunteers after they got their second shots.
The companies also said they have tried to recruit a diverse pool of volunteers, to match more closely the groups most severely affected by the pandemic. “Approximately 42% of global participants and 30% of U.S. participants have racially and ethnically diverse backgrounds, and 41% of global and 45% of U.S. participants are 56-85 years of age,” Pfizer said.
The 150 clinical trials sites in United States, Germany, Turkey, South Africa, Brazil and Argentina will continue to collect information about efficacy and safety for two more years.