Interim Clinical Considerations for Use of COVID-19 Vaccines Currently Approved or Authorized in the United States

CDC now recommends that people aged 65 years and older, residents in long-term care settings, and people aged 50–64 years with underlying medical conditions should receive a booster shot of Pfizer-BioNTech’s COVID-19 Vaccine at least 6 months after completing their Pfizer-BioNTech primary series. Other groups may receive a booster shot based on their individual risk and benefit. 

 https://www.cdc.gov/vaccines/covid-19/clinical-considerations/covid-19-vaccines-us.html?CDC_AA_refVal=https://www.cdc.gov/vaccines/covid-19/info-by-product/clinical-considerations.html#pregnant