The Expert Committee on COVID-19 Vaccination (EC19V) in Singapore has been closely reviewing the data regarding the need for additional vaccine doses, and recommends that the persons aged 80 years and above receive a second booster dose (i.e. fourth dose if receiving an mRNA vaccine) from about five months after receiving their first booster dose.

This recommendation is also applicable to persons living in aged care facilities, such as nursing homes; and medically vulnerable persons who are at increased risk of severe disease due to significant medical risk factors.

Local data to date shows protection against severe disease is sustained after the third dose mRNA booster. However, there can be waning of protection, particularly in the elderly and medically vulnerable. International studies show that vaccine efficacy against hospitalisation declines after a third dose mRNA booster. In the US CDC report for the Omicron-dominant period, vaccine efficacy against hospitalisation was 91 per cent at 2 months after the third dose and decreased to 78 per cent by the fourth month. Similar findings were also reported by the UK Health Security Agency.