Fourth dose of bivalent COVID-19 vaccine more protective than monovalent booster in study
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Key takeaways:
- Compared with a monovalent vaccine, a fourth dose of a bivalent COVID-19 vaccine provides added protection.
- These results were true for both SARS-CoV-2 naïve patients and those who were previously infected.
A fourth dose of a bivalent COVID-19 vaccine provided added protection for previously infected and SARS-CoV-2 naive patients compared with a fourth dose of a monovalent vaccine, researchers in Singapore found.
The researchers studied real-world observational data to compare the effectiveness of receiving — as a fourth COVID-19 shot — a bivalent vaccine targeting both the original, wild strain of SARS-CoV-2 and the omicron variant or a fourth dose of one of the original monovalent COVID-19 vaccines (not the recently approved updated monovalent boosters).
“The benefit of bivalent vaccines over monovalent vaccines remains unclear, and some in-vitro studies have found that neutralizing antibody and T-cell responses elicited by bivalent mRNA vaccines targeting BA.5 were similar to those elicited by monovalent vaccines,” Celine Y. Tan, MPH, a researcher in the Communicable Diseases Division of the Singapore Ministry of Health, told Healio.
“Real-world observational data on effectiveness of bivalent vaccines are also scarce. There had not been real-world studies comparing the effectiveness of monovalent and bivalent vaccines against symptomatic SARS-CoV-2 infection when administered as fourth doses,” Tan said.
Bivalent COVID-19 vaccines from both Moderna and Pfizer-BioNTech outperformed their original monovalent vaccines, according to data released separately by both companies in November 2022, a few months after they were authorized for use.
Tan and colleagues conducted a retrospective cohort study among Singapore residents aged 18 years and older who had received three monovalent mRNA vaccine doses and were eligible for a fourth dose. They then analyzed the incidence of medically attended symptomatic SARS-CoV-2 infection and COVID-19-related hospital admission between Oct. 14, 2022, and Jan. 31, 2023, by previous infection status and type of fourth vaccine dose received.
In total, 2,749,819 individuals were included in the analysis. The researchers found that for those who were SARS-CoV-2-naïve, a fourth monovalent vaccine dose did not provide additional protection compared with three monovalent doses against symptomatic infection (HR = 1.09; 95% CI, 1.07–1.11), while the bivalent vaccine provided additional protection (HR = 0.18; 95% CI, 0.17–0.19).
Results were similar among participants with previous COVID-19 infection in regard to receiving a fourth monovalent dose or a bivalent dose (HR = 0.87; 95% CI, 0.84–0.91 vs. HR = 0.14; 95% CI, 0.13–0.15).
Additionally, the study showed that the bivalent vaccine provided more protection against COVID-19-related hospital admission among participants who were SARS-CoV-2 naïve and those who were previously infected (HR = 0.12; 95% CI, 0.08–0.18 vs. HR = 0.04; 95% CI, 0.01–0.15) compared with the fourth monovalent dose for both SARS-CoV-2-naïve participants (HR = 0.84; 95% CI, 0.77-0.91) and in those previously infected participants (HR = 0.85; 95% CI, 0.69–1.04).
Tan and colleagues concluded that these findings highlight that a fourth dose of a bivalent vaccine provides added protection against infection and hospital admission and might be preferred over a monovalent vaccine.
In an accompanying commentary, Ronen Arbel, MBA, PhD, health outcomes researcher, and Yael Wolff-Sagy, PhD, head of the research and information department, both at Clalit Health Services in Tel Aviv, Israel, wrote that these findings also highlight the “futility of the monovalent booster” in SARS-CoV-2-naïve patients and limited protection in previously infected people.
“In the post-pandemic era the world is entering, it is vital to understand the absolute benefit of vaccinations,” they wrote.
Arbel and Wolff-Sagy cited a previous analysis of a U.S. study showed that the number needed to vaccinate to avoid one COVID-19 death in participants aged younger than 65 years exceeds 100,000.
“The analysis by Tan and colleagues of number needed to vaccinate to prevent medically attended symptomatic SARS-CoV-2 infections, which shows favorable numbers needed to vaccinate ranging from 40 to 105 in the various subgroups by age and previous infections, is another important contribution of this study,” they wrote
References:
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Tan CY, et al. Lancet Infect Dis. 2023;doi:10.1016/S1473-3099(23)00373-0
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