Second dose given within a grace period of fewer than 4 days from the recommended date for the second shot are considered valid and do not need to be repeated. The second shot should be given as close to the recommended time as possible, but vaccinations given outside of the recommended times do not need to be repeated. Visit CDC’s Interim Clinical Considerations for Use of mRNA COVID-19 Vaccines Currently Authorized in the United States (https://www.cdc.gov/vaccines/covid-19/info-by-product/clinical-considerations.html) for more information.