Bivalent COVID-19 vaccines provide added protection, real-world data show
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Real-world data showed that bivalent messenger RNA vaccines against SARS-CoV-2 provided “significant additional protection” against symptomatic COVID-19 among people who had received two, three or four previous monovalent doses.
The study, published Tuesday in MMWR, evaluated the relative vaccine effectiveness of the bivalent boosters compared with receiving two or more monovalent shots during a period when omicron BA.4, BA.5 and their sublineages predominated.
“These findings support the current COVID-19 vaccination policy recommending a bivalent booster dose for adults who have completed at least a primary mRNA vaccination series, irrespective of the number of monovalent doses previously received,” researchers wrote.
The study used data collected through the Increasing Community Access to Testing national COVID-19 testing program. The researchers analyzed data from 360,626 nucleic acid amplification tests performed on adults aged 18 years or older between Sept. 14 and Nov. 11 at 9,995 retail pharmacies in the United States. The adults reported symptoms consistent with COVID-19 and no immunocompromising conditions.
Of those receiving a test, 121,687 (34%) tested positive for COVID-19. Of the positive tests, 28,874 (24%) were not vaccinated, 87,013 (72%) had received at least two monovalent booster doses but no bivalent dose, and 5,800 (5%) had received a bivalent booster dose.
Of the 238,939 people who tested negative for COVID-19, 72,010 (30%) were not vaccinated, 150,455 (63%) had received at least one monovalent booster dose but no bivalent dose, and 16,474 (7%) had received a bivalent booster.
The researchers found that relative vaccine effectiveness of a bivalent booster compared with receiving two or more monovalent vaccine doses more than 3 months earlier and more than 8 months earlier was 30% and 56% among people aged 18 to 49 years, 31% and 48% among people aged 50 to 64 years, and 28% and 43% for people aged older than 65 years, respectively.
The researchers noted that the relative benefits of the bivalent booster increased with time since receipt of their previous monovalent booster.
The FDA authorized the bivalent COVID-19 vaccine boosters made by Moderna and Pfizer-BioNTech in August.
“Bivalent booster doses provided significant additional protection against symptomatic SARS-CoV-2 infection during a period when omicron variant BA.4/BA.5 lineages and their sublineages predominated. All persons should stay up to date with recommended COVID-19 vaccines, including bivalent booster doses, if it has been more than 2 months since their last monovalent vaccine dose,” the researchers wrote.
Perspective
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It’s important to have clinical efficacy numbers on the bivalent boosters to understand how well they work in the real world. One conclusion that can be drawn from the data is that efficacy is better the longer since last vaccination and that, for low-risk individuals, it is likely better to wait 8 months or so after the last vaccination to gain maximal benefit (vs. the 2 months that is recommended).
However, these data are not able to answer whether there was a benefit in updating the vaccines from the original formulation, how long the efficacy against infection holds and how applicable it is in a world dominated by BA.4/BA.5, which the vaccine targets.
Overall, a transient benefit against infection was not surprising, but the larger debate over whether boosting low-risk people to prevent mild infection transiently vs. concentrating on targeting boosters to those at high risk for severe disease continues.
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