Relative effectiveness of monovalent and bivalent mRNA boosters in preventing severe COVID-19 due to omicron BA.5 infection up to 4 months post-administration in people aged 60 years or older in Italy: a retrospective matched cohort study
The Lancet Infectious Diseases·
- DOI
- 10.1016/s1473-3099(23)00374-2
- PMID
- 37478877
- PMCID
- —
- OpenAlex
- W4384701934
- Study type
- Cohort study
- Publisher
- Elsevier BV
- Article type
- journal-article
- Integrity
- current
Why this research matters now
Second mRNA booster doses provided additional protection against severe COVID-19 in adults aged 60 years and older beyond that offered by the first booster. The bivalent vaccine targeting the original strain plus BA.4-5 offered greater protection than monovalent boosters and sustained effectiveness up to four months, informing booster recommendations for older populations during omicron BA.5 circulation.
Structured evidence summary
Research question
The study aimed to estimate the relative effectiveness of second booster doses using monovalent or bivalent mRNA vaccines in preventing severe COVID-19 among older adults in Italy.
Study design
This retrospective matched cohort study linked Italian vaccination registry and surveillance system data from September 2022 to January 2023. Each person aged 60 years or older who received a second booster was matched 1:1 with someone who had received only the first booster at least 120 days earlier. Cox proportional hazard models were used to estimate relative vaccine effectiveness.
Population and setting
The study included 2,129,559 matched pairs of individuals aged 60 years or older in Italy during a period when omicron BA.5 was the predominant circulating subvariant.
Main findings
Against severe COVID-19 during days 14-118 post-administration, relative vaccine effectiveness was 50.6% for the bivalent original/BA.4-5 booster, 49.3% for the bivalent original/BA.1 booster, and 26.9% for the monovalent booster. The bivalent original/BA.4-5 booster showed similar effectiveness in those aged 60-79 years (53.6%) and those 80 years or older (48.3%). Protection decreased over time but remained evident at four months post-administration.
Public-health relevance
Second mRNA booster doses provided additional protection against severe COVID-19 in adults aged 60 years and older beyond that offered by the first booster. The bivalent vaccine targeting the original strain plus BA.4-5 offered greater protection than monovalent boosters and sustained effectiveness up to four months, informing booster recommendations for older populations during omicron BA.5 circulation.
Important limitations
This summary is limited to the supplied single-article abstract and metadata and requires the original paper for decision-grade interpretation.
GIDS interpretation
The classifier links indicate this article addresses COVID-19 surveillance, vaccination, and vaccine effectiveness in Italy. It may be discoverable through disease-specific (COVID-19, SARS), geographic (Italy), or topic-based (surveillance, vaccination, vaccine effectiveness) queries within the GIDS literature corpus.
Related GIDS surveillance
Literature context does not validate, explain, or change a surveillance signal. Exact and contextual relationships are shown separately.
Evidence relationships
This article has 11 auditable classifier relationships to diseases, places, topics, and study design.