When and how will we know if we need Covid-19 booster shots?

There’s a lot we don’t yet know about the data behind Pfizer and BioNTech’s renewed push to change its two-shot Covid vaccination series to a three-shot regimen. But as the sides bicker about whether a third shot is going to be needed, one thing is certain: The final decision will not rest with the company.

Public health officials, not pharmaceutical executives, will be making the final call on when and whether booster shots will be needed. Pfizer and other manufacturers will surely try to push for approvals; Moderna is already testing a Delta-variant specific booster. Depending on how their conversations go with vaccine regulators at the Food and Drug Administration, companies may apply for a change to their emergency use authorizations (or to the vaccine license, if they secure one before applying to change their vaccine label to a three-dose one.

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