What is a bivalent COVID-19 vaccine?
Simply put, a “bivalent” vaccine is a type of vaccine that protects against a combination of two or more coronavirus strains.
This helps to create a broader immune response and improves the strength and duration of protection against the most dominant COVID-19 variants in circulation.
What about bivalent boosters for the BA.4 and BA.5 Omicron strains?
Health Canada recently approved an updated Pfizer-BioNTech Comirnaty COVID-19 vaccine targeting the dominant circulating Omicron subvariants BA.4 and BA.5, as well as the original strain of the virus.
Moderna’s updated vaccine, Spikevax, which was approved in September, is different in that it targets only the original strain and the BA.1 Omicron subvariant. Health Canada says clinical trials suggest Moderna’s bivalent booster elicits a “stronger immune response” against the more recent mutations of Omicron — BA.4 and BA.5 — than the original Moderna vaccine.
Both the Moderna and Pfizer-BioNTech bivalent shots are expected to offer better protection against the circulating Omicron strains.
How is it different from the previous vaccines?
The bivalent vaccines contain two messenger RNA (mRNA) components instead of one.
One of the components is from the original strain of the coronavirus, while the other component is from the Omicron strain, according to the U.S. Food and Drug Administration (FDA). However, it is only approved for use as a booster dose.