目前CDC说FDA批准以及WHO批准的疫苗如果完成要求针数了，视为公共卫生要求的完全免疫（considered fully vaccinated for the purpose of public health guidance），不需要另打。看你信不信CDC了。 楼上说的间隔28天是针对非FDA和非WHO批准的疫苗。 https://www.cdc.gov/vaccines/covid-19/clinical-considerations/covid-19-vaccines-us.html#people-vaccinated-outside-us Some people may have received a COVID-19 vaccine that is not currently approved or authorized in the United States. Limited data are available on the safety or efficacy of receiving a COVID-19 vaccine currently approved or authorized in the United States after receipt of a non-FDA-approved or FDA-authorized COVID-19 vaccine. However, in some circumstances people who received a COVID-19 vaccine not currently approved or authorized in the United States may be offered revaccination with an FDA-approved or FDA-authorized vaccine. COVID-19 vaccines neither approved nor authorized by FDA but listed for emergency use by the World Health Organization (WHO)2 People who have received all recommended doses of a COVID-19 vaccine that is listed for emergency use by WHO do not need any additional doses with an FDA-approved or FDA-authorized COVID-19 vaccine. People who have not received all the recommended doses of a COVID-19 vaccine listed for emergency use by WHO may be offered a complete, FDA-approved or FDA-authorized COVID-19 vaccine series. COVID-19 vaccines neither approved or authorized by FDA nor listed for emergency use by WHO People who received all or some of the recommended doses of a COVID-19 vaccine that is neither approved or authorized by FDA nor listed for emergency use by WHO may be offered a complete, FDA-approved or FDA-authorized COVID-19 vaccine series. The minimum interval between the last dose of a non-FDA-approved or non-FDA-authorized vaccine or a WHO-listed vaccine and an FDA-approved or FDA-authorized COVID-19 vaccine is 28 days. Only people who have received all recommended doses of an FDA-approved, FDA-authorized, or WHO-listed COVID-19 vaccine are considered fully vaccinated for the purpose of public health guidance.
https://www.cdc.gov/vaccines/covid-19/clinical-considerations/covid-19-vaccines-us.html#people-vaccinated-outside-us
Some people may have received a COVID-19 vaccine that is not currently approved or authorized in the United States. Limited data are available on the safety or efficacy of receiving a COVID-19 vaccine currently approved or authorized in the United States after receipt of a non-FDA-approved or FDA-authorized COVID-19 vaccine. However, in some circumstances people who received a COVID-19 vaccine not currently approved or authorized in the United States may be offered revaccination with an FDA-approved or FDA-authorized vaccine. COVID-19 vaccines neither approved nor authorized by FDA but listed for emergency use by the World Health Organization (WHO)2 People who have received all recommended doses of a COVID-19 vaccine that is listed for emergency use by WHO do not need any additional doses with an FDA-approved or FDA-authorized COVID-19 vaccine. People who have not received all the recommended doses of a COVID-19 vaccine listed for emergency use by WHO may be offered a complete, FDA-approved or FDA-authorized COVID-19 vaccine series. COVID-19 vaccines neither approved or authorized by FDA nor listed for emergency use by WHO People who received all or some of the recommended doses of a COVID-19 vaccine that is neither approved or authorized by FDA nor listed for emergency use by WHO may be offered a complete, FDA-approved or FDA-authorized COVID-19 vaccine series. The minimum interval between the last dose of a non-FDA-approved or non-FDA-authorized vaccine or a WHO-listed vaccine and an FDA-approved or FDA-authorized COVID-19 vaccine is 28 days. Only people who have received all recommended doses of an FDA-approved, FDA-authorized, or WHO-listed COVID-19 vaccine are considered fully vaccinated for the purpose of public health guidance.