Bivalent COVID-19 mRNA vaccines: All You Need to Know

With both the Pfizer Comirnaty bivalent COVID-19 booster vaccine and the bivalent Moderna/Spikevax vaccine available for residents in Singapore, Singaporeans now have 2 bivalent vaccine options to choose from when it is their turn to receive a booster.

Dr Edwin Chng, medical director at Parkway Shenton, answers some commonly asked questions about the 2 recently approved bivalent COVID-19 mRNA vaccines – what they are, their side effects, effectiveness, and who can take them.

What is a bivalent COVID-19 vaccine?

When a vaccine is 'bivalent', it means that the vaccine stimulates an immune response against 2 different antigens. In the case of bivalent COVID-19 vaccines, this means protection against 2 different variants of the COVID-19 virus – the original SARS-CoV-2 virus, and the Omicron variant(s).

Specifically, the bivalent Moderna/Spikevax vaccine targets the original SARS-CoV-2 strain and the Omicron BA.1 variant, while the Pfizer Comirnaty bivalent COVID-19 booster vaccine targets the original SARS-CoV-2 strain and the Omicron BA.4 and BA.5 variants.

Compared with the original mRNA vaccines, these new bivalent COVID-19 vaccines offer added protection against newer COVID-19 variants, including XBB.

How do the bivalent COVID-19 vaccines offer better protection?

Since the bivalent COVID-19 mRNA vaccines target both the original and Omicron variants of the COVID-19 virus, they help the body mount a broader immune response when these viruses are detected. This helps to increase the strength and duration someone is protected against current COVID-19 variants, and may also offer better protection against future variants.

According to clinical trials, the bivalent Moderna/Spikevax vaccine is capable of generating an antibody response that is 75% better than the original vaccine against the Omicron variant, resulting in better protection against severe disease. The Health Sciences Authority said that it may also stimulate antibodies from the Omicron BA.4/5, Alpha, Beta, Delta and Gamma variants.

Are the bivalent COVID-19 vaccines safe?

Both bivalent versions of the Moderna/Spikevax and Pfizer Comirnaty vaccines have similar safety profiles as their originals, and are regarded as safe. Like the original COVID-19 vaccines offered, the observed side effects have been mostly mild-to-moderate, and go away within a few days.

Common adverse side effects include:

• Injection site pain, redness, or swelling
• Fatigue
• Fever
• Headaches
• Muscle and joint pains
• Chills
• Swollen lymph nodes
• Nausea and vomiting

Who can receive the bivalent COVID-19 vaccines?

Individuals who have completed their primary COVID-19 vaccinations and are eligible to receive their COVID-19 vaccine boosters can receive these bivalent COVID-19 vaccines.

Those aged 18 and above will be able to receive the bivalent Moderna/Spikevax vaccine, whereas those aged 12 and above will be able to receive the Pfizer Comirnaty bivalent COVID-19 booster vaccine.

Where can I receive the bivalent COVID-19 vaccines?

The bivalent Moderna/Spikevax vaccine is being offered at the Joint Testing and Vaccination Centres (JTVCs), while the Pfizer Comirnaty bivalent COVID-19 booster vaccine is available at the JTVCs, clinics, and polyclinics.

If you're aged 12 – 49 years, you will receive an SMS to book an appointment for additional COVID-19 booster doses. Please visit www.gowhere.gov.sg/vaccine to find a vaccination location near you.