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SINGAPORE: The Health Sciences Authority (HSA) on Tuesday (Oct 25) granted interim authorisation for Pfizer’s Comirnaty bivalent COVID-19 booster vaccine in Singapore.

This makes it the second such jab to be approved for use here after the Moderna/Spikevax vaccine, which obtained interim authorisation in September and was rolled out earlier in October.

The Comirnaty Bivalent (Original/Omicron BA.4/5) COVID-19 jab by Pfizer is an updated version of the original Comirnaty vaccine.

It comprises two components – 15 micrograms targeting the original SARS-CoV-2 strain and 15 micrograms targeting the Omnicron BA.4 and BA.5 variants, said HSA in a news release.

The Comirnaty bivalent vaccine is authorised for use as a booster shot for individuals aged 12 and above, who have received primary series COVID-19 vaccination.

Health Minister Ong Ye Kung has said that bivalent vaccines provide better protection against newer COVID-19 variants compared to the original vaccines.

Last week, he announced that Singapore plans to invite people aged between 18 and 49 to take their COVID-19 bivalent vaccines later in the year, as more supplies are secured.

Earlier in October, the Government said it expects Pfizer’s Comirnaty bivalent vaccine to be available in Singapore by the end of the year. 

It also announced then that children aged between five and 11 will be able to receive the Comirnaty vaccine as a booster dose.


Official vaccination recommendations on the use of this booster will be issued by the Expert Committee on COVID-19 Vaccination and the Ministry of Health (MOH) in due time, added HSA. 

In making its regulatory decision, HSA said it consulted experts from its Medicines Advisory Committee and Panel of Infectious Diseases Experts.

The authorisation was based on evidence including from Pfizer’s non-clinical studies, clinical trials with different variant-updated vaccines and manufacturing and quality processes.

With the clinical study by Pfizer for its Comirnaty Bivalent (Original/Omicron BA.4/5) Vaccine still under way, the assessment of its efficacy was based primarily on an earlier clinical study conducted in individuals aged above 55 – but with the Comirnaty Bivalent (Original/Omicron BA.1) Vaccine instead.

“HSA considers such data as relevant taking into account that these Omicron subvariants are closely related,” said the authority.

The study showed that the bivalent vaccine elicited a stronger immune response against the targeted Omicron BA.1 variant, while preserving adequate response against the original SARS-CoV-2 strain, said HSA.

An ongoing clinical study with the bivalent (Original/Omicron BA. 4/5) vaccine also showed, in 80 participants aged 18 and above, consistent trends of higher immune responses against the Omnicron BA. 4/5 variant, and continued response against the original SARS-CoV-2 strain.

Safety data from the clinical studies showed that the bivalent vaccine was generally well-tolerated and the safety profile was consistent with what is known for the original vaccine, said HSA.

“The adverse events were mostly mild-to-moderate, such as injection site pain and/or tenderness, fatigue, headache and muscle pain,” it added.

“These reactions are generally associated with vaccinations and expected as part of the body’s natural response to build immunity against COVID-19. They usually resolve on their own within a few days.”

HSA said that based on the available information, it has assessed that the benefits are expected to outweigh the risks.

It said it will continue to actively monitor the safety of the vaccine and require Pfizer to submit data from the ongoing clinical study, to ensure that the benefits continue to outweigh the risks.

HSA added that it will take the necessary actions and provide updates to the public if significant safety concerns are identified.