Frequently asked questions

• Are the vaccines safe?

  The vaccine is deemed to be safe based upon a rigorous evaluation of currently available scientific evidence. If the available scientific evidence changes or if new information becomes available, the authorization for its use can be adapted.

  The Pfizer vaccine study enrolled 43,538 participants, with 42% having diverse ethnic backgrounds. No serious safety concerns were observed. The only Grade 3 (severe) adverse events greater than or equal to 2% in frequency were fatigue (3.8%) and headache (2%).

  The Moderna vaccine study enrolled 30,000 participants, with 37% having diverse backgrounds. No serious safety concerns were observed. The majority of adverse events were mild or moderate in severity. Grade 3 (severe) events included injection site pain (2.7%), fatigue (9.7%), muscle pain or soreness (8.9%), joint pain (5.2%), headache (4.5%), pain (4.1%) and redness at the injection site (2%).

  All vaccine trials have scheduled monitoring reviews, typically by an independent group known as a Data and Safety Monitoring Board, which routinely assesses safety or can be convened quickly to review any unanticipated adverse events.

• Did the COVID-19 vaccine go through a clinical trial?

  Yes. Operation Warp Speed was an effort to develop vaccines and therapeutics quicker than would normally be possible by running the three phases of these clinical trials in an accelerated time frame. They also start manufacturing on a large scale before the studies are done, so that vaccines will be ready to be administered as soon as possible once they're approved, having been declared effective and safe. All of the vaccines go through the standard steps, but in a much faster process made possible, in part, by the large number of patients available to participate in each trial.

  This six-minute video (https://youtu.be/Z06JQhyZLUI) and the illustration below further explain these points.

  How many people received the vaccine during the trials?

  The Pfizer vaccine study enrolled 43,538 participants. The Moderna vaccine study enrolled 30,000 participants.