The companies said that of 170 cases of Covid-19, 162 were in the placebo group and eight were in the vaccine group. Out of 10 cases of severe Covid-19, nine had received a placebo.
Pfizer and BioNTech said the vaccine’s effectiveness was consistent across age, race and ethnicity. The most common serious adverse event was fatigue. 3.7 percent of the volunteers reported drowsiness after taking the second dose. Two percent of the volunteers reported a headache after the second dose. Older adults reported fewer and milder side effects, the companies said.
“It’s pretty amazing,” said Akiko Iwasaki, an immunologist at Yale University. She said the results in people over 65 were the most promising. “We know from the influenza vaccine that in this age group it is very difficult to get protection with vaccines,” she said. The 94 percent effectiveness in this group “is truly remarkable.”
Federal health officials have stated that the first doses of the vaccines will most likely go to groups like health care workers who are at high risk of exposure, as well as those most susceptible to the disease, such as the elderly.
Dr. Saad B. Omer, director of the Yale Institute for Global Health, said the results showing that the vaccines protect people from serious illnesses are also good news because the first goal with such limited availability is not initially going to stop the transmission of the disease, but to prevent people from getting extremely sick. “So that’s very comforting,” he said.
He urged Pfizer to quickly publish a more detailed analysis of the data – beyond the original press release – so that the scientists can evaluate the results more thoroughly. The companies have announced that they will submit the results for review in a scientific journal. This process can take weeks or months. “These are not normal times, this is a pandemic and important policy actions are being taken,” said Dr. Omer. “It’s always better to set guidelines for scientific data, not a press release.”
In addition to the results of its clinical study, Pfizer said it was ready to contact the F.D.A. Agency recommended two-month safety data and detailed manufacturing records that show the company can consistently produce high quality batches of its product. The F.D.A. will review the data and ask an external panel of vaccine experts to weigh up the application, a process that can take weeks.