Last month, the U.S. Food and Drug Administration approved an updated COVID-19 bivalent booster, specifically to target the Omicron variant. Starting this fall, Moderna and Pfizer will offer these boosters to provide protection as COVID-19 infection rates are expected to rise.
A bivalent vaccine is a vaccine that contains two strains, or two slightly genetically different versions, of a virus. According to Prof. Cynthia Leifer, microbiology and immunology, bivalent vaccines are created for extra protection against new viral strains that arise over time.
The COVID-19 bivalent booster is not the only vaccine with more than one strain of virus. Many vaccines, such as the flu and MMR vaccines, contain multiple strains of a virus or even different viruses.
Half of the contents in the COVID-19 bivalent booster are mRNA from the original COVID-19 strain while the other half includes mRNA from the Omicron strain.
mRNA are pieces of genetic material used to synthesize proteins. In the COVID-19 virus, mRNA allows the production of spike proteins, proteins located on the surface of COVID-19 viruses that allow entry of the viruses into host cells. Once the spike proteins are in the body, the immune system learns to develop a response and attack against them.
Because the immune system can fight against multiple antigens, vaccines with multiple viruses do not change in efficacy compared to their monovalent counterparts. However, it reduces the number of shots necessary to combat against all strains of a virus. Thus, it allows our immune system to provide better protection against more viral strains.
“The bivalent COVID booster works by reminding our immune system of the original strain and introducing the new variant,” Leifer said.
The COVID-19 bivalent booster contains the Omicron variant as opposed to other strains of COVID-19 because of Omicron’s high infection rate. Omicron is now responsible for 90 percent of COVID-19 cases and is predicted to spread during the fall and winter season due to reasons such as decreasing COVID-19 immunity and cold weather that drives people indoors and allows for more spread of infection.
Although the original COVID-19 vaccine and boosters reduced rates of symptomatic infection, severe disease, hospitalization and death from the original Alpha and newer Delta strain infection, it is ineffective in reducing symptomatic infection for Omicron.
However, studies have shown that the updated bivalent booster causes high levels of antibodies against the original Alpha strain and reasonable levels of antibodies against the Omicron strain.
The FDA analyzed data of 600 people over the age of 18 who all received the first dose of the Moderna monovalent booster and then received either another dose of the monovalent booster or a dose of the bivalent booster. A stronger immune response was observed from the individuals who received the Moderna bivalent booster dose after the first monovalent booster dose.
Additionally, an estimate of over 100,000 hospitalizations can be prevented in the upcoming month through administration of the bivalent booster.
All individuals who received the initial booster are eligible to receive the bivalent booster after two months. The Moderna booster can be given to those ages 18 and up while the Pfizer booster can be given to those ages 12 and up.
The bivalent COVID-19 booster, like the original version, has similar side effects and takes up to two weeks to have full effects. Additionally, it is also still possible to become infected even after receiving the booster.
As cases continue to persist, many health experts compare making new COVID-19 vaccines to the yearly flu shots. Although there is still uncertainty about this, COVID-19 boosters will most likely be frequently updated to combat against newly arising strains or increase effectiveness against the infection.
Prof. Leifer even believes that one day there may be a multivalent vaccine that protects against COVID-19 and the flu.
“While Biden confidently claimed the pandemic is over, not all scientists and epidemiologists agree,” Prof. Leifer said. “What everyone does agree on is that COVID-19 is here to stay.”