Both Pfizer and Moderna are working on bivalent booster vaccines made up of both the old formula and a new one that targets the Omicron BA.4 and BA.5 subvariants of the coronavirus.
Mandatory Credit: Frederic J. Brown/AFP/Getty Images
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Updated Covid-19 boosters are expected in September. Will it be too late?
This fall, Americans could get boosted with a mRNA Covid-19 vaccine unlike any that's come before.
