COVID-19 vaccines are not recommended for post-exposure prophylaxis to prevent SARS-CoV-2 infection. Unvaccinated people who were close contacts of a person with SARS-CoV-2 infection should typically not seek vaccination until quarantine has ended; this is to reduce the risk of transmission to others (e.g., healthcare personnel, other clinic patients), because vaccination is not expected to prevent SARS-CoV-2 infection that could occur after the exposure for which the person is in quarantine, and to avoid confusion between vaccination side effects and symptoms of COVID-19.
However, to avoid missed opportunities for vaccination, vaccination during quarantine could be considered during outreach and contact tracing activities or at the time of post-exposure SARS-CoV-2 testing in certain circumstances. Examples might include when people 1) are likely to have repeated SARS-CoV-2 exposures because they are unable to effectively quarantine (e.g., residing in a congregate or crowded setting or during outbreaks in their community), or, 2) will have limited access to vaccination after their quarantine period has ended, or, 3) are unlikely to otherwise seek vaccination after their quarantine period has ended. In such situations, the person recommended for quarantine can receive vaccination as long as 1) they do not have symptoms consistent with COVID-19, and, 2) appropriate infection prevention and control procedures are employed during vaccination. Furthermore, unvaccinated people who are being tested for SARS-CoV-2 may be candidates for same-day vaccination if they do not have symptoms consistent with COVID-19.
People should be counseled that COVID-19 vaccines are effective, especially at preventing serious COVID-19 illnesses. However, they should also be informed that vaccination may not prevent SARS-CoV-2 infection until 2 weeks after the primary series is completed, i.e., will not prevent them from getting COVID-19 from the current exposure but should help protect them from infection after future exposures. In addition, SARS-CoV-2 viral testing may be necessary to differentiate between common post-vaccination symptoms and symptoms of SARS-CoV-2 infection:
People who develop signs and symptoms not associated with the COVID-19 vaccination (e.g., cough, shortness of breath, runny nose, sore throat, loss of taste or smell) should isolate and be evaluated for SARS-CoV-2 infection as soon as possible.
People who develop signs and symptoms that could be from either COVID-19 vaccination or SARS-CoV-2 infection (e.g., fever, fatigue, headache, myalgia) without typical COVID-19 symptoms described above, and are clinically stable, should isolate and, if symptoms do not improve by two days post-vaccination, be evaluated for SARS-CoV-2 infection.