How Effective Are the Bivalent Boosters? CDC Shares New Real-World Data on Updated Shots


man getting covid vaccine

man getting covid vaccine

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  • New data shows the updated bivalent COVID vaccines provide additional protection against COVID-19.
  • The updated boosters are now considered to be more effective against current Omicron subvariants than the original monovalent vaccine.
  • The boosters are expected to also provide protection against new and emerging Omicron subvariants—including BQ.1 and BQ.1.1—but experts say it’s still too soon to tell.

New data on the updated COVID-19 vaccines suggest the bivalent boosters are more effective against current strains of the virus compared to the original vaccines.

The Centers for Disease Control and Prevention (CDC) last week published a report in the Morbidity and Mortality Weekly Report showing the first real-world evidence that the bivalent booster provides “significant additional protection against symptomatic SARS-CoV-2 infection.”

The benefit of the bivalent boosters also increased with time since a person’s last monovalent COVID vaccine. Effectiveness jumped from 30% in study participants ages 18–49 who received an original vaccine two to three months ago, to 56% if they received a monovalent COVID vaccine eight or more months earlier.

The real-world findings come following updated clinical trial data from both Pfizer-BioNTech and Moderna on their bivalent boosters earlier in November. Both companies’ bivalent boosters produced significantly higher immune responses, compared to the original COVID-19 vaccines, with similar safety and tolerability profiles.

Combined, the data suggests that all eligible people should receive a bivalent COVID booster in order to stay up to date on vaccinations for continued protection against the virus.

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Real-World Data, Clinical Trials Show Bivalent Vaccine Effectiveness

For the CDC study, researchers used data from the Increasing Community Access to Testing (ICATT) national SARS-CoV-2 testing program, which included more than 360,000 nucleic acid amplification tests (NAATs) from nearly 10,000 retail pharmacies. The tests were administered between September 14–November 11, 2022 among people ages 18 and older who had COVID symptoms.

The relative vaccine effectiveness of a bivalent booster dose—compared to two more more monovalent vaccine doses—depended on the time between shots. For people ages 18–49 who received a monovalent dose two to three months earlier, the effectiveness was 30%; for the same group who received a monovalent dose eight or more months earlier, effectiveness rose to 56%.

Relative vaccine effectiveness also decreased slightly as age increased: Among people ages 50–64, bivalent vaccines were 31% and 48% effective depending on time since last monovalent shot; among people ages 65 and older, it was 28% and 43% effective.

Prior to the CDC study, both Moderna and Pfizer-BioNTech shared new clinical trial data from their updated COVID vaccines. Though the company data sets don’t look at the boosters’ ability to prevent COVID cases or severe disease, they do look at lab measurements of antibodies—one of the components of the immune system that fights viruses—and their ability to neutralize the SARS-CoV-2 virus.

According to Kawsar Talaat, MD, an associate professor of international health at the Johns Hopkins Bloomberg School of Public Health and vaccine expert, antibody data is typically a pretty good indicator of how well a vaccine will do in the real world.

"What we have seen in the past is when we compare effectiveness data with antibody data, is that antibody data tends to predict how well people are protected," said Dr. Talaat.

In a press release from Pfizer, the company reported its booster increased antibodies 4-fold against the BA.4 and BA.5 Omicron variants in people older than 55, compared to the original COVID vaccines in the same age group. A month after receiving a booster dose of the bivalent vaccine, antibodies increased 13.2-fold in adults older than 55, and 9.5-fold in adults 18 to 55. This is compared to just 2.9-fold with the original vaccine. 

Moderna’s data showed consistent immune responses among all participants, which ranged from age 18 to 65. In a press release, the company reported an average 15.1-fold increase in antibodies compared to pre-booster levels. In those who had a previous COVID infection before receiving the booster, antibody levels increased 26.4-fold; for those without a prior infection, antibodies increased 9.8-fold.

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Bivalent Boosters’ Effectiveness Against Future Variants

According to the latest CDC data, new Omicron subvariants—particularly BQ.1 and BQ.1.1—are overtaking the BA.4 and BA.5 subvariants the bivalent boosters are tailored to.

According to Sherif Mossad, MD, an infectious disease physician at Cleveland Clinic, we won’t be able to understand just how effective the new boosters are against new or future variants until they become more prevalent.

But the updated boosters do have a broader range of protection compared to the monovalent vaccine, Jennifer Bourgeois, PharmD, a pharmacist expert at SingleCare, tells Health. The bivalent vaccine contains targets from both the Omicron variants as well as those from the original strain of SARS-CoV-2. By having more targets, there’s more of a chance that the bivalent vaccine will still be able to elicit an immune response to future variants.

In the company’s press release, Moderna Chief Executive Officer Stéphane Bancel also said data has shown the bivalent vaccine to offer some protection against BQ.1.1 specifically.

“Our bivalent boosters also show, in research assays, neutralizing activity against BQ.1.1, an increasingly dominant emerging variant,” said Bancel, “confirming that updated vaccines have the potential to offer protection as the virus continues to evolve rapidly to escape our immunity.”

Dr. Talaat is also hopeful that the updated boosters will maintain effectiveness against new and emerging Omicron subvariants—but maintains that only time will tell for sure.

“They do have the same spike protein, which means they have the same vaccine target areas, so the vaccine is expected to work against those as well,” said Dr. Talaat. “But what will happen in the next three to six months, it’s too soon to tell.”

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Don’t Delay Getting the Updated Booster

If you haven’t already gotten the new bivalent vaccine, Bourgeois recommends doing so as soon as you can.

“I recommend all adults, especially those 65 and over and anyone with underlying health conditions, should protect themselves with the most broad vaccine available, which is the updated booster,” said Bourgeois.

The upcoming holiday season is also a good reason to get boosted sooner rather than later, to have high antibody levels when family gatherings commence, said Dr. Talaat.

One thing to keep in mind with the updated boosters—and most vaccines, for that matter—is that they may not fully protect against infection, but will protect against severe illness, hospitalization, and death.

“It’s not perfect, you can get boosted and still get COVID,” said Dr. Talaat. “When we saw the original data from the first vaccines we didn’t test for protection against infection we tested for symptomatic disease, and they protected against that very well. But the reality is we have never been very good at preventing infection and transmission of respiratory illnesses.”