Also Read- Pfizer says early data signals COVID-19 vaccine is effective
Could that sneak peek have come earlier?
Pfizer’s initial plans called for evaluating when just 32 infections had been counted. But many scientists warned that was simply too small to draw conclusions about a vaccine needed by billions.
Pfizer said it reconsidered, going back to the FDA for permission to change the plan and do its first interim analysis when there were more cases. By the time Pfizer made the change and caught up with a backlog of virus tests, the DSMB had 94 infections to analyse.
The higher number increases confidence in those still preliminary results, said Dr Jesse Goodman, a former FDA vaccine scientist now at Georgetown University.
Moderna, AstraZeneca and other companies not quite as far along in their final testing all have set slightly different timepoints for when their data monitors will peek at how the shots are working.
Don’t forget safety
Safety is the top priority. Monitors also watch for unexpected or serious side effects. Earlier this fall, separate studies of vaccine candidates made by AstraZeneca and Johnson & Johnson were temporarily halted after some participants experienced health problems, delaying the research until safety investigations allowed both to resume.
Pfizer said Monday no serious safety concerns have emerged so far with its vaccine.
But the FDA is requiring that companies track at least half of study volunteers for two months to look for side effects before asking the agency to review their vaccine. That’s about when side effects have cropped in studies of other vaccines.
Pfizer and Moderna both expect to reach that safety milestone later in November.
What happens then?
Companies are expected to seek permission for “emergency use” of their vaccines, rather than waiting to fully complete their studies and then seeking traditional approval.
The FDA’s scientific advisers will debate each company’s study findings in a public meeting before the agency decides.
Manufacturers already have begun stockpiling vaccine doses in anticipation of eventual approval, but the first shots will be in short supply and rationed. And the first people vaccinated will need to undergo extra safety tracking, as the government watches for rare side effects that might crop up when the shots are given to many more people than were in the research studies.