The Expert Committee on COVID-19 Vaccination (EC19V) in Singapore recommends that all vaccinated persons aged 18 years and above should receive a booster vaccine dose at about five months after the last dose of their primary vaccine course, or as soon as possible thereafter, in order to maintain good protection against COVID-19. The booster dose should not be delayed beyond nine months after the primary vaccine course.

Local and international data show reduced vaccine protection against COVID-19 infection from around six months after completion of the last vaccine dose in the primary vaccination series or earlier. The level of protection drops even further over time.

There is also some reduction in protection against severe disease, particularly in older persons. In addition, international studies have shown that the protection against Omicron variant infection by a primary vaccination series is weaker compared to previous variants, and that boosters increase the protection against infection and severe illnesses caused by Omicron. As such, booster vaccination is crucial to ensure continued protection against COVID-19.

Persons who had received two or more doses of the Sinovac-CoronaVac or Sinopharm vaccines as part of a three-dose primary vaccination series are strongly recommended to receive one dose of an mRNA vaccine as a booster dose.