Bivalent mRNA booster effective, ‘essential’ for older adults
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Key takeaways:
- Bivalent mRNA booster vaccine efficacy for preventing hospitalization was 72%.
- Bivalent mRNA booster vaccine efficacy for preventing mortality was 68%.
Bivalent messenger RNA booster vaccinations were effective for preventing COVID-19 hospitalizations and deaths in older adults, according to data presented at the European Congress of Clinical Microbiology & Infectious Diseases.
“[This study was prompted by the fact that] the FDA approval was based only on safety and immune response studies,” Ronen Arbel, PhD, health outcomes researcher at the community medical services division of Clalit Health Services, told Healio. “There was no evidence of the effectiveness of the bivalent vaccine in preventing severe COVID-19.”
To assess the effectiveness of a bivalent mRNA vaccine booster dose to reduce COVID-19 hospitalizations and deaths, Arbel and colleagues conducted a retrospective, population-based, cohort study in Israel between Sept. 27, 2022, and Jan. 25, 2023.
According to the study, they used data from electronic medical records in Clalit Health Services (CHS) and included all members of CHS who were aged 65 years or older and eligible for a bivalent mRNA COVID-19 booster vaccination.
Hospital records were used to identify hospitalizations and deaths. The researchers then compared rates of hospitalizations and deaths between patients who received a bivalent mRNA booster vaccination and those who did not.
In total, 569,519 eligible participants were identified, 134,215 (24%) of whom received a bivalent mRNA booster vaccination during the study period. The study showed that COVID-19 hospitalization occurred in 32 participants who received a bivalent mRNA booster vaccination and 541 who did not (adjusted HR = 0.28; 95% CI, 0.19-0.4).
Further analysis showed that the absolute risk reduction for COVID-19 hospitalizations in bivalent mRNA booster recipients vs. nonrecipients was 0.089% (95% CI, 0.075%-0.101%), and the number needed to vaccinate to prevent one hospitalization due to COVID-19 was 1,118 people (95% CI, 993-1,341).
Additionally, death caused by COVID-19 occurred in 13 patients who received a bivalent mRNA vaccination and 172 who did not (aHR = 0.32; 95% CI, 0.18-0.58). The researchers found that older age and male sex were most associated with higher risk of death, whereas socioeconomic status score did not impact risk of death, although previous SARS-CoV-2 infection was associated with a reduced risk of death.
Absolute risk reduction of death was 0.027%, and accordingly, one death due to COVID-19 could be avoided for every 3,722 people vaccinated, according to the study.
The authors wrote that these data show bivalent mRNA booster vaccination in adults aged 65 years or older is effective and essential.
“Our findings highlight the importance of bivalent mRNA booster vaccination in populations at high risk of severe COVID-19,” Arbel said.
In a related commentary, Anna Stoliaroff-Pepin, and Thomas Harder, MD, both of the Robert Koch Institut, wrote that these data back up most of the currently available data which show high effectiveness of these boosters against hospitalization and death, although, they added that this study specifically adds to important data showing the public health impact of these vaccines.
“To illustrate the public health impact, Arbel and colleagues calculated the respective number needed to vaccinate to prevent one event for both outcomes in their study,” they wrote. “While the number needed to vaccinate to prevent one COVID-19-related hospitalization was high (1,118 people), it was higher still to prevent one COVID-19-related death (3,722). As health care resources are scarce in many countries, we need to consider the settings and populations in which bivalent booster vaccines are beneficial.”
Stoliaroff-Pepin and Harder called for additional studies in the future to assess different populations with different health economic evaluations to improve the evidence base for vaccination programs.
References:
- Arbel R, et al. Lancet Infect Dis. 2023;doi:10.1016/S1473-3099(23)00122-6.
- Stoliaroff-Pepin A, et la. Lancet Infect Dis. 2023;doi:10.1016/S1473-3099(23)00187-1.
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Arbel R, et al. Effectiveness of a bivalent mRNA vaccine booster dose to prevent severe COVID-19 outcomes: a retrospective cohort study. Presented at: European Congress of Clinical Microbiology and Infectious Diseases; April 15-18, 2023; Copenhagen, Denmark.
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