The FDA already approved third doses of the Pfizer vaccine and is expected to approve the Moderna and Johnson & Johnson vaccines for booster shots shortly, as well. For example, if all three were approved for boosters, and mixing-and-matching was approved, a person who received two doses of the Moderna vaccine last spring could receive a booster from any of the three vaccines.
FDA expected to approve mixing-and-matching COVID-19 vaccines for booster shots

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