Over the years of the COVID-19 pandemic, SARS-CoV-2, the virus that causes the disease, has mutated many times. Each new version of the virus is called a variant or subvariant.  The same COVID-19 vaccines that were made available since December 2020 have done a remarkable job in preventing severe disease and death but have become less effective at preventing infections because of the mutations.

That is, until the late summer of 2022, when the U.S. Food and Drug Administration (FDA) and the Centers for Disease Control and Prevention (CDC) green-lighted “bivalent” formulations—an updated version of the vaccines—to be used against the newer variants of SARS-CoV-2.

Bernard Camins, MD, MSc, Professor of Medicine (Infectious Diseases) at the Icahn School of Medicine at Mount Sinai and the Medical Director for Infection Prevention for the Mount Sinai Health System, explains what the bivalent vaccines do and the latest guidance on who should receive them and when.

New Guidance on COVID-19 Vaccines: In April 2023, the Food and Drug Administration and the Centers for Disease Control and Prevention announced some major changes for COVID-19 vaccines. Click here to read more about what you need to know.

What does it mean that the vaccines are bivalent?

COVID-19 vaccines with bivalent formulations target the BA.5 subvariant of Omicron—one of the predominant circulating variants—as well as the original SARS-CoV-2 virus, says Dr. Camins. These include the vaccines from Pfizer-BioNTech and Moderna.

An updated vaccine is needed because the virus has mutated several times and is so different from the original strain that the previous monovalent version of the vaccine —targeting only one variant—might not provide adequate protection from infection, he says.

With bivalent vaccines now authorized for use, the monovalent versions of the COVID-19 boosters are no longer authorized. The primary series are still recommended before the bivalent booster can be administered.

How effective and safe is the updated vaccine compared to previous ones?

“It’s pretty much the same as the old vaccine,” Dr. Camins says. The difference is that the genetic makeup of the updated vaccines has an addition to account for the spike protein of BA.5.

The updated vaccines’ side effects are similar to previous versions. The most commonly reported side effects of the bivalent vaccines include pain, redness, and swelling at the injection site, fatigue, headache, muscle pain, joint pain, chills, swelling of the lymph nodes in the same arm of the injection, nausea/vomiting, and fever, according to the FDA.

“You probably would not notice it being different from any of the previous vaccine doses or boosters you’ve received,” Dr. Camins says.

The updated Moderna and Pfizer-BioNTech vaccines have both been studied for effectiveness and safety. Although the studies examined a bivalent formulation involving the original strain and Omicron BA.1, the FDA granted the vaccines authorization based on the totality of evidence, which included clinical and nonclinical data that demonstrated commonalities between BA.1 and BA.4/BA.5.

This method of studying and approving updated COVID-19 vaccines is similar to how new flu vaccines based on circulating strains are handled, he adds: “It is very analogous to what we do with the flu vaccine.”

Who is eligible for the updated vaccine and who should get it?

The Moderna updated booster is authorized for individuals ages 6 and older, while the Pfizer-BioNTech updated booster is authorized for those who are 5 and older.

Where can I get the updated vaccine?

If you live in the New York metropolitan region, you can check the New York StateNew York CityNew Jersey, or Connecticut websites for locations that offer appointments or walk-in vaccination. Major pharmacy chains are another place to try. If you live elsewhere, Dr. Camins recommends using vaccines.gov or reaching out to local health care providers and pharmacies.

When should I get the updated booster?

The updated vaccine is recommended to individuals two months after completing a primary series or a previous booster.

I got COVID-19 recently. Do I still need the updated booster?

“The updated booster is recommended even for those who have been infected with a previous variant or subvariant of SARS-CoV-2,” says Dr. Camins.

If you have been recently infected, it is reasonable to wait 90 days after symptom onset before receiving an updated booster, he says. However, the CDC has indicated it is also safe to seek an updated booster as soon as you are no longer contagious from a current infection.

Why do I need a booster when people still seem to get COVID-19 despite being vaccinated?

The updated vaccine booster was created to match the current circulating BA.5 subvariant better so it should protect patients from infection better than the previous version, although it’s not a 100 percent guarantee, Dr. Camins says. Receiving the booster could also lessen the chances of developing severe disease especially for patients who are at high risk for complications from COVID-19.

Will I need to keep taking updated boosters if there are new variants?

“We don’t know if future updated boosters are required,” Dr. Camins says. That determination could be based on the current circulating sub-variant, as well as the data from people who have received the updated booster for Omicron BA.5, he adds.

However, Dr. Camins notes that the White House’s COVID-19 Response Team is thinking of moving in the direction of rolling out annual, updated COVID-19 shots matched to current circulating strands. A single annual shot should provide a high degree of protection against serious illness all year, and could prevent thousands of deaths and hospitalizations annually, according to White House officials.

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