FDA says Pfizer COVID vaccine is highly effective, even after first dose

The coronavirus vaccine manufactured by Pfizer and BioNTech is highly effective and poses no significant safety risks, according to documents published by a Food and Drug Administration (FDA) advisory panel Tuesday.

The positive results could mean that FDA clearance for the two-dose vaccine could come shortly after the Vaccines and Related Biological Products Advisory Committee meets on Thursday to publicly review the evidence.

“Safety data from approximately 38,000 participants … suggest a favorable safety profile, with no specific safety concerns identified that would preclude issuance of an EUA [emergency use authorization],” agency staff wrote.

Agency staff conducted their own analysis of the research presented by the companies and found the vaccine was 95 percent effective at preventing COVID-19 infection a week after the second dose was administered. 

However, the results also show some protection begins even after the first dose. COVID cases tapered off in the vaccinated group shortly after the first dose was administered; 50 cases of COVID-19, compared with 275 cases in the placebo group, according to the report.

Despite the evidence of protection, the FDA said the trial did not have a single-dose arm to make an adequate comparison, so they can’t make a conclusion about the efficacy of a single dose.

The vaccine is designed to be administered in two doses, three weeks apart. 

It’s also unclear how long protection lasts. The report showed protection at least through the two month monitoring period required by the FDA, but it has not been possible to monitor for longer.

The vaccine has side effects, but most people reported relatively mild fevers, fatigue, muscle aches and injection site pain. 

The vaccine also appears to work the same across different populations,  with a high efficacy rate in both men and women, as well as white, Black and Latino people.

There is currently not enough data to make conclusions about the safety of the vaccine in children less than 16 years of age, pregnant women and people with compromised immune systems, the agency said.

When the FDA formally clears the vaccine, initial doses are expected to be shipped within hours, with Trump administration officials targeting 6.4 million doses distributed in the first week.