Covids, variants and sub-variants: what is a bivalent vaccine?
The next step of the COVID-19 booster rollout will involve a “bivalent” vaccine that targets the ever-evolving Omicron variant. The vaccine isn’t here yet, but will likely be available in the fall
What is a bivalent vaccine? And how is it different from current boosters?
Bivalent Vaccines Target 2 Viral Strains
A bivalent vaccine elicits an immune response against two different antigens. This can means two different viruses, or two variations of one virus.
The current COVID-19 vaccines and boosters target the original type of COVID-19 discovered in late 2019. They are considered “monovalent” vaccines.
Pfizer is creating a bivalent vaccine that will target both the original type of COVID-19 and the Omicron variant. Specifically, it will target the spike protein associated with the BA.1 subvariant of Omicron.1
Moderna’s bivalent vaccine candidate is designed to target newer Omicron subvariants of BA.4 and BA.5 alongside the original strain of COVID.
Multivalent Vaccines Aren’t New
Despite the media attention, the COVID bivalent vaccine candidates aren’t groundbreaking firsts. In fact, other vaccines have been designed to protect against even more than two types of viruses.
Various degrees of multivalent vaccines have existed in the U.S. for years, and are used to protect people against conditions like sexually transmitted infections (STIs), flu, and pneumonia.
Some (non-COVID) multivalent vaccines include:
- Gardasil-9: Gardasil is a vaccine that targets nine strains of human papillomavirus virus (HPV), a common STI.2
- Influenza vaccine: All U.S. flu vaccines are quadrivalent, targeting four different strains of flu.3
- Pneumococcal polysaccharide vaccine (PPSV23): This vaccine targets 23 types of bacteria that cause pneumococcal disease, protecting against pneumonia, ear infections, sinus infections, meningitis, and bacteremia.4
Why Are Multivalent Vaccines Useful?
Rather than create multivalent versions of a vaccine, manufacturers could devise many different vaccines to target each unique variant or subvariant of a virus like COVID-19.
But as we’ve seen with the vaccine rollout so far, formulating, testing, authorizing, and distributing any vaccine is no easy task. Combination candidates make the process a little easier.
In addition, researchers suggest that multivalent vaccines alleviate the burden of having to routinely get several different shots—and routinely experience their side effects.5
Are These the Best Bivalent Candidates?
While the pending Moderna and Pfizer bivalent COVID vaccines show promising protection against Omicron, some experts have questioned whether they are the right bivalent candidates at the right time. After all, a new type of Omicron, or another COVID-19 variant, may appear by the fall.
Fortunately, as health authorities have repeated for months, vaccines for any COVID strain will protect against severe disease and death, even if they become less effective at preventing transmission.
- Pfizer. Pfizer and BioNTech announce Omicron-adapted COVID-19 vaccine candidates demonstrate high immune response against Omicron.
- Centers for Disease Control and Prevention. Human papillomavirus (HPV) vaccination: what everyone should know.
- Centers for Disease Control and Prevention. Quadrivalent influenza vaccine.
- Centers for Disease Control and Prevention. Pneumococcal polysaccharide VIS.
- Lauer KB, Borrow R, Blanchard TJ. Multivalent and multipathogen viral vector vaccines. Clin Vaccine Immunol. 2017;24(1):e00298-16. doi:10.1128/CVI.00298-16