Pfizer’s Comirnaty bivalent vaccine granted interim authorisation by HSA

Pfizer’s Comirnaty (Original/Omicron BA.4/5) bivalent vaccine was granted interim authorisation under the Pandemic Special Access Route by the Health Sciences Authority (HSA) on Tuesday (Oct 25). 

This is the second bivalent vaccine to be granted an interim authorisation by HSA, following Moderna’s Spikevax Bivalent Original/Omicron COVID-19 vaccine on Sep 14.

According to a press release by HSA on Tuesday, the Comirnaty bivalent vaccine is an updated version of the original Comirnaty vaccine. It is authorised for use as a booster vaccine for those aged 12 years old and above and have received the COVID-19 primary series vaccination.

The vaccine comprises two mRNA components, where 15 micrograms target the original SARS-CoV-2 strain and another 15 micrograms that target the Omicron BA.4 and BA.5 variants.

HSA added that official vaccination recommendations on the use of the bivalent vaccine will be issued by the Expert Committee on COVID-19 Vaccination and the Ministry of Health in due time.

The authorisation of the Comirnaty bivalent vaccine was based on “the totality of available evidence”, including Pfizer’s non-clinical studies, clinical trials with different variant-updated vaccines, and its quality and manufacturing processes, explained HSA.

HSA assessed that the benefits of using the bivalent vaccine as a booster “outweigh the risks”, adding that it consulted experts from its Medicines Advisory Committee and Panel of Infectious Diseases Experts. 

It concluded that bivalent vaccines provide a “broader immunity and better protection against the SARSCoV-2 virus”, citing Pfizer’s Phase 3 clinical study conducted in those aged above 55 years old with the Corminaty bivalent (Original/Omicron BA.1) vaccine.

The study showed that the bivalent vaccine elicited a stronger immune response against the targeted Omicron BA.1 subvariant, while still maintaining an adequate response against the original SARS-CoV-2 strain, according to HSA.

It added that the “observed immune responses” were also supported by an ongoing Phase 2/3 clinical study by Pfizer with the bivalent (Original/Omicron BA. 4/5) vaccine.

The ongoing study found that a preliminary analysis of 80 participants aged 18 years and above showed “consistent trends” of higher immune responses against the Omicron BA. 4/5 subvariant and “continued response” against the original SARS-CoV-2 strain.

The decision to extend the bivalent vaccine’s use on adults and adolescents aged above 12 years was also based on immune responses, and its effectiveness and safety.

HSA explained that compared to the older population that has weaker immune systems due to old age, the younger population “generally develops a higher immune response”. Based on this, it is expected that the bivalent vaccine would trigger “comparable or better” immune response in adolescents than older adults.

Safety data from clinical studies also showed that the bivalent vaccine was “generally well-tolerated”, said HSA. 

It added that adverse events – injection site pain and/or tenderness, fatigue, headache and muscle pain – were mostly mild to moderate and are expected as part of the body’s natural response to build immunity against COVID-19.

These reactions are associated with vaccinations and usually resolve on their own within a few days.