Severity and outcomes of Omicron variant of SARS-CoV-2 compared to Delta variant and severity of Omicron sublineages: a systematic review and metanalysis
BMJ Global Health·
- DOI
- 10.1136/bmjgh-2023-012328
- PMID
- 37419502
- PMCID
- PMC10347449
- OpenAlex
- W4383550993
- Study type
- Systematic review
- Publisher
- BMJ
- Article type
- journal-article
- Integrity
- current
Why this research matters now
The findings indicate substantially reduced disease severity with Omicron compared to Delta, which has implications for healthcare resource planning and public health response strategies during variant transitions.
Structured evidence summary
Research question
The review aimed to compare the severity and clinical outcomes of SARS-CoV-2 Omicron variant infection with Delta variant infection, and to compare outcomes between Omicron sublineages BA.1 and BA.2.
Study design
This was a systematic review and meta-analysis of 42 studies comparing clinical outcomes between variants. A random-effects model was used to pool relative risk estimates, and heterogeneity was assessed using the I² index.
Population and setting
The review included patients infected with either Omicron or Delta variants of SARS-CoV-2. Twenty-nine of the 42 included studies adjusted for vaccination status, while 12 had no such adjustment.
Main findings
Compared to Delta, Omicron infection was associated with 61% lower risk of death, 56% lower risk of hospitalization, and reduced risk of ICU admission, oxygen therapy, and ventilation. No statistically significant difference in hospitalization risk was found between Omicron sublineages BA.1 and BA.2.
Public-health relevance
The findings indicate substantially reduced disease severity with Omicron compared to Delta, which has implications for healthcare resource planning and public health response strategies during variant transitions.
Important limitations
This summary relies on the supplied abstract and metadata only. Twelve of the 42 included studies did not adjust for vaccination status, which may confound severity comparisons. Full assessment of study heterogeneity, risk of bias details, and methodological limitations requires review of the complete published article.
GIDS interpretation
The systematic review provides aggregated evidence on variant-specific severity patterns. The disease classifier links to SARS and COVID-19 reflect the pathogen and disease under study, while treatment and vaccination topic tags indicate that clinical management context was relevant to included studies.
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 10 auditable classifier relationships to diseases, places, topics, and study design.