How effective is the bivalent mRNA SARS-CoV-2 vaccine in preventing COVID-19 hospitalizations and deaths?

In a recent study posted on Lancet preprint*, researchers investigated the efficacy of a bivalent messenger ribonucleic acid (mRNA) vaccine against the severe consequences of coronavirus disease 2019 (COVID-19).

Background

The bivalent mRNA vaccine contains components of the ancestral severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) strain and the Omicron BA.4/5 substrain. The United States (US) Food and Drug Administration approved his bivalent vaccine booster from Pfizer and Moderna for adult use in August 2022. A bivalent vaccine has been approved for booster vaccination in Israel for those at high risk of severe his COVID-19.

clinical data effectiveness of Bivalent vaccines with randomized controlled trials are in short supply. Nonetheless, preliminary evidence from the United States indicates significant protection with bivalent boosters against severe disease, with efficacy estimates ranging from 38% to 73%. Still, the efficacy of bivalent boosters in preventing COVID-19 hospitalization and death remains unclear.

About research

In this study, researchers evaluated the efficacy of a bivalent mRNA booster in preventing COVID-19-related hospitalizations and deaths in Israel. They used electronic medical record data from a large health service (Clalit Health Services, CHS) covering her two-thirds of her 65+ population in Israel.

The cohort consisted of CHS members aged 65 years and older who were eligible for bivalent vaccination. Individuals who had been infected or vaccinated within the past 3 months and who had not completed their first vaccination were excluded. The primary and secondary endpoints of the study were her COVID-19 hospitalization and death, respectively.

The team extracted information on subject demographics, COVID-19 test dates and results, vaccination dates, hospitalizations, and mortality. Data on risk factors for severe disease were also collected. They tested all covariates for interaction with bivalent vaccination. Variables meeting the test criteria were included in the multivariate regression analysis.

A multivariate Cox proportional hazards model with time-dependent covariates was used to estimate the association between covariates and bivalent booster intake and COVID-19 hospitalization and mortality. The model was adjusted for sociodemographic factors and comorbidities.

findings

Researchers identified 622,701 people who met the inclusion criteria. Of these, 85,314 were boosted with her bivalent mRNA vaccine from Pfizer. Boosted individuals were more likely to be older and male than others in the cohort. Vaccination coverage was significantly higher among adults aged 75 years and older and those of high socioeconomic status, but lower among ultra-Orthodox Jews and Arabs.

COVID-19-related hospitalizations occurred in 6 bivalent vaccinees and 297 who did not. The crude event rate was 0.27 per 100,000 man-days risk, with an adjusted hazard ratio of 0.19. Male gender and age were associated with higher rates of hospitalization for COVID-19. In contrast, Arabs had lower hospitalization rates.

History of chronic obstructive pulmonary disease (COPD), chronic renal failure (CRF), chronic heart failure (CHF), and stroke were significantly associated with increased hospitalization risk. COVID-19-related deaths occurred in one bivalent vaccinee and her 73 others who were not boosted with the bivalent vaccine. Age, COPD, CHF, and stroke history were significantly associated with increased mortality risk.

Conclusion

In summary, the researchers noted that bivalent booster vaccination in eligible populations was associated with an 81% reduction in COVID-19-related hospitalizations. It was also associated with an 86% reduction in mortality. In particular, there was a low response rate for bivalent vaccination among eligible subjects (14%) due to vaccine misinformation, belief that vaccination was unnecessary, or reports of side effects.

Taken together, these results suggest that bivalent vaccination is associated with a reduced risk of severe COVID-19 in older adults and that increased efforts are needed to encourage vaccination among eligible populations. indicates that

*Important Notices

Lancet preprints publish non-peer-reviewed, preliminary scientific reports and should be considered definitive, to guide clinical practice/health-related actions, or to be treated as established information. not.