MOH and NCID Highlight Need for Three-Dose Regimen for Better Defence Against Delta Variant
A Singapore study conducted by the Ministry of Health (MOH) and the National Centre for Infectious Diseases (NCID) has revealed that the Sinovac-CoronaVac COVID-19 vaccine offers significantly lower protection against severe disease caused by the Delta variant compared to mRNA vaccines.
Study Findings on Vaccine Effectiveness
The study, which analysed local data from 1.25 million people between October and November, showed the following effectiveness against severe disease:
Sinovac-CoronaVac: 60%
Pfizer-BioNTech/Comirnaty: 90%
Moderna: 97%
Severe disease was defined as requiring oxygen support, intensive care unit (ICU) admission, or resulting in death due to COVID-19.
Recommendations for Sinovac Recipients
MOH and NCID emphasised the necessity of a three-dose primary series for those vaccinated with Sinovac. They recommended completing the series with a dose of an mRNA vaccine, such as Pfizer-BioNTech/Comirnaty, for stronger protection.
International findings further support this approach. Preliminary data from Chile indicate that receiving Pfizer-BioNTech/Comirnaty as the third dose after two Sinovac doses reduces infection risk by 95%, compared to a 71% reduction when Sinovac is used as the third dose. Antibody levels also rose 27 times higher with an mRNA third dose.
National Vaccination Programme Updates
From January 1, 2022, Singapore will consider individuals fully vaccinated only if they have received three doses of Sinovac or Sinopharm vaccines.
Authorities are closely monitoring the performance of mRNA and non-mRNA vaccines, especially in conjunction with booster doses. MOH and NCID urged all eligible individuals to receive their boosters when offered, to ensure optimal protection.
