Do Omicron COVID Vaccine Booster Shots Protect Against Infection? Top Doc Explains

The new U.S. boosters are combination, or “bivalent,” shots

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How well will the new bivalent COVID booster shots protect against infection from the newest variants and mutations, including the now-dominant omicron subvariant BA.5?

While health officials have said vaccines continue to show effective protection, particularly when it comes to severe outcomes of the virus, experts hope the newest shots could go even further.

"One of the reasons we're really excited about this updated COVID vaccine is because, different than for the last year or so, we're back to having a match," Chicago Department of Public Health Commissioner Dr. Allison Arwady said Tuesday. "So this updated vaccine - kind of like at the beginning those first vaccines were highly protective, we weren't seeing a lot of breakthrough... now again, while it is a good match, I would expect there to be significantly more protection against infection as well."

She notes, however, that no vaccine is 100%.

Until now, COVID-19 vaccines have targeted the original coronavirus strain, even as wildly different mutants emerged. The new U.S. boosters are combination, or “bivalent,” shots. They contain half that original vaccine recipe and half protection against the newest omicron versions, called BA.4 and BA.5, that are considered the most contagious yet.

The combination aims to increase cross-protection against multiple variants.

The move by the FDA tweaks the recipe of shots made by Pfizer and rival Moderna that already have saved millions of lives. The hope is that the modified boosters will blunt yet another winter surge.

"We are back right now to a 99% match between what we are seeing spread and the protection that the vaccine can give," Arwady said. "And my worry is we're going to miss the window. People aren't going to choose to get that updated booster and we will miss the opportunity on an individual level, but more importantly on the societal level to be in the best possible shape heading into winter. I don't know whether we're going to see a new variant emerge in the way omicron did last year. I certainly hope not, but the more people can be matched to what is circulating now, the protection will be better."

Appointments to receive the updated shots have been ramping up in Chicago-area pharmacies, with Illinois health officials urging community members to get the new dose.

“These new bivalent vaccines are designed to offer extra protection against the omicron variants, which are now the dominant strain of the virus," Illinois Department of Public Health Director Dr. Sameer Vohra said in a statement. "Getting up to date now is especially important for those who are at risk of serious outcomes, as the updated vaccines offer protection from hospitalization and even death.”

More than 188,000 Illinois residents have been given a dose of the newly-updated bivalent COVID-19 booster shots as of last week.

As a result of increasing demand for the bivalent vaccines, daily vaccination numbers have reached their highest point since February, the Illinois Department of Public Health said Friday. More than 21,000 daily doses have been administered, on average, over the past week, which is twice the daily average throughout the majority of summer.

The vaccine is now the primary shot that will be administered to those who are eligible and looking to get boosted throughout the country.

Who is Eligible?

According to the Centers for Disease Control and Prevention, only those who have completed a full COVID vaccine series -- which consists of either two Moderna or Pfizer shots, or one Johnson & Johnson shot -- are eligible to receive the modified booster. Additionally, the shots have certain age restrictions, which are listed below:

  • Individuals 18 and older are eligible to receive either Pfizer’s or Moderna’s updated COVID booster shot
  • Only Pfizer booster doses can be administered to those aged 12 through 17
  • While those younger than 18 years old are eligible for the new COVID booster, they aren't eligible for the Moderna dose

Can you mix-and-match?

Here's the CDC's guidance on mixing and matching for boosters, based on which shots you have already received.

  • People ages 18 years and older may get a different product for a booster than they got for their primary series, as long as it’s Pfizer-BioNTech or Moderna.
  • Teens ages 12-17 years may get a different product for a booster than they got for their primary series, as long as it’s Pfizer-BioNTech.
  • Children ages 5 through 11 years who got a Pfizer-BioNTech primary series must also get Pfizer-BioNTech for a booster.
  • People ages 12 years and older may only get the updated (bivalent) mRNA (Pfizer-BioNTech or Moderna) booster. They can no longer get an original (monovalent) mRNA booster.
  • Novavax is not authorized for use as a booster dose at this time.

The Booster Shot Side Effects

With the arrival of the long-awaited COVID-19 booster shots geared to target BA.4 and BA.5 omicron subvariants, many may be curious about its possible side effects as they prepare for another vaccination.

Turns out, the new boosters may not be much different from your last dose.

"We just don't have any data on this [yet], essentially giving two vaccines in one shot — but biologically, I just wouldn't expect the side effects, severity or the safety profile of the shots to be different from the current mRNA vaccines and boosters," Dr. Paul Offit, director of the Vaccine Education Center at Children's Hospital of Philadelphia and member of an independent advisory group to the U.S. Food and Drug Administration, told CNBC's Make It.

The FDA states that those who receive the bivalent vaccine "may experience side effects commonly reported by individuals who receive authorized or approved monovalent mRNA COVID-19 vaccines."

Among the side effects study participants who received the shots most commonly reported were:

  • pain, redness or swelling where the shot was administered
  • fatigue
  • headache
  • muscle pain
  • join pain
  • chills
  • swelling of the lymph nodes in the arm where the shot was given
  • nausea or vomiting
  • fever

The side effects were similar for both Moderna and Pfizer's vaccines and largely mirror expected side effects for earlier doses.

The CDC stated that side effects with the third shot were also "similar to that of the two-dose series."

The most common symptoms then included fatigue and pain at the injection site, but "most symptoms were mild to moderate."

As with previous doses of the vaccine, the CDC notes that, "serious side effects are rare, but may occur."

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