evidence: As part of a bigger plan, the FDA also announced that the current bivalent mRNA vaccines will replace the original monovalent Moderna and Pfizer-BioNTech mRNA COVID-19 vaccines, which target the original, or ancestral, SARS-CoV-2 virus strain; they are no longer authorized for use in the U.S. [...] Because the monovalent (original) mRNA COVID-19 vaccines are no longer authorized for use in the U.S., unvaccinated children 6 months through 4 years of age may receive a three-dose primary series of the Pfizer-BioNTech bivalent vaccine. Those who are unvaccinated and 6 months through 5 years of age may get a two-dose primary series of the Moderna bivalent vaccine. Children in the above-mentioned age groups who have already received one, two, or three doses of a monovalent COVID-19 vaccine may get a bivalent shot, but the number of doses they receive will depend on the type of vaccine (Moderna or Pfizer) they’ve already received, their age, and vaccination history.