CNA Explains: What is a bivalent COVID-19 vaccine, and how will it protect me?

SINGAPORE: The Health Sciences Authority (HSA) announced on Wednesday (Sep 14) that it has granted interim authorisation to Moderna’s bivalent COVID-19 vaccine as a booster shot, under the Pandemic Special Access Route (PSAR).

Spikevax Bivalent Original/Omicron COVID-19 vaccine is the first bivalent vaccine against the coronavirus to be authorised as a booster here. HSA said it consulted experts from its Medicines Advisory Committee and Panel of Infectious Diseases Experts in making the regulatory decision.

The authority added that its clinical review was based on an ongoing Phase 2/3 trial conducted by Moderna in individuals aged 18 and above.

Here's what you need to know before scheduling your next booster shot:

WHAT IS A BIVALENT VACCINE?

Bivalent vaccines are so-called because they work by simulating an immune response against two different antigens, such as viruses.

Multivalent vaccines - which protect against more than one type of antigen - have been around for a long time.

In fact, if you’re a woman, you may have taken one of them already – Gardasil-9 is currently used in Singapore as a vaccine against diseases caused by several types of the Human Papillomavirus, or HPV, including cervical cancer.

Your annual influenza jab is also an example. It's quadrivalent, which means it protects you from four virus types: Two influenza A viruses and two influenza B viruses.

HOW IS THIS VACCINE DIFFERENT FROM OTHER COVID-19 VACCINES?

The COVID-19 vaccines used in Singapore until now have been monovalent, which means they only contain or encode the spike protein of the original SARS-CoV-2 virus.

In comparison, Moderna’s bivalent vaccine has been updated to protect against the Omicron BA.1 variant in addition to the original strain. It contains 25 micrograms each of the components targeting the two viruses.

HSA said its clinical review showed that the booster vaccine “elicited a strong immune response against the Omicron BA.1 variant, while preserving the immune response against the original SARS-CoV-2 strain”.

It added that preliminary data from an exploratory analysis suggested that the vaccine may stimulate antibodies from other variants, including the Omircon BA.4/5, Alpha, Beta, Delta and Gamma.

WHO CAN TAKE THIS BOOSTER VACCINE?

People who are aged 18 and above and who have received their primary COVID-19 vaccine doses are eligible to receive the bivalent shot.

Official recommendations will be issued by the expert committee on COVID-19 vaccination and the Ministry of Health “in due time”, said HSA.

WHAT ARE THE SIDE EFFECTS?

Clinical studies have shown that the bivalent vaccine was “generally well-tolerated” and has a safety profile consistent with Moderna’s original Spikevax vaccine.

Side effects were mostly mild to moderate, HSA said. This includes pain and/or tenderness at the injection site, fatigue, headache and muscle pain.

The authority noted that these are “generally associated with vaccinations and expected as part of the body’s natural response to build immunity against COVID-19”, which usually resolve on their own within a few days.

IS ANYONE ELSE DEVELOPING A BIVALENT COVID-19 VACCINE?

Yes. Pfizer-BioNTech has a bivalent vaccine that works similarly to Moderna’s and targets the same two strains of COVID-19 virus. It has been approved in some countries as a single-dose booster for individuals aged 12 and above.

Singapore has yet to authorise this vaccine for use in the country. However, Health Minister Ong Ye Kung said on Tuesday that MOH is bringing both types of vaccine into Singapore under agreements with the pharmaceutical companies.

“Our intention is to update our vaccines for the National Vaccination Programme as the formulations improve,” said Mr Ong said.