The Expert Committee on COVID-19 Vaccination (EC19V) has been closely reviewing the data regarding the need for additional vaccine doses, and recommends that the following groups of persons receive a second booster dose (i.e. fourth dose if receiving an mRNA vaccine) from about five months after receiving their first booster dose:
a. All persons aged 80 years and above;
b. Persons living in aged care facilities, such as nursing homes; and
c. Medically vulnerable persons who are at increased risk of severe disease due to significant medical risk factors1.
2. 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% at 2 months after the third dose and decreased to 78% by the fourth month. Similar findings were also reported by the UK Health Security Agency.
3. Persons aged 80 years and above, and persons with comorbidities are at increased risk of severe disease. They will be most affected by waning vaccine efficacy over time. Data from Israel’s rollout of the fourth dose also shows that the benefits are greatest in persons aged 80 years and above.
4. EC19V therefore recommends that persons aged 80 and above should receive a second booster dose (i.e. fourth dose if receiving an mRNA vaccine). Persons in aged care facilities such as nursing homes tend to have comorbidities and should similarly be vaccinated even if they have not reached 80 years of age. Vulnerable persons who are at increased risk of severe disease due to significant medical risk factors should also be vaccinated. These include persons with chronic diseases of the heart, lungs, kidneys, liver and other organ systems.
5. Healthy persons in younger age groups have a lower risk of severe disease, and better immune responses to vaccination. There is currently no recommendation for them to receive an additional dose of vaccine after the first booster dose.
6. As EC19V had previously recommended, immunocompromised persons are recommended to receive three doses as part of their primary enhanced series and to receive the first booster dose (i.e. fourth dose) around five months after the third dose. There is no recommendation for a second booster dose for this group currently.
7. EC19V will continue to monitor the data and developments around COVID-19 vaccination and will update its recommendations based on the latest scientific and clinical evidence.
EXPERT COMMITTEE ON COVID-19 VACCINATION
24 MARCH 2022
 Vulnerable persons may receive a second booster dose as recommended by their doctors. Vulnerable persons are individuals who are at increased risk of severe disease due to significant medical risk factors. These include persons with chronic diseases of the heart, lungs, kidneys, liver and other organ systems.