Facing the Omicron variant—how well do vaccines protect against mild and severe COVID-19? Third interim analysis of a living systematic review
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Abstract
Background: The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron variant is currently the dominant variant globally. This third interim analysis of a living systematic review summarizes evidence on the effectiveness of the coronavirus disease 2019 (COVID-19) vaccine (vaccine effectiveness, VE) and duration of protection against Omicron. Methods: We systematically searched literature on COVID-19 for controlled studies, evaluating the effectiveness of COVID-19 vaccines approved in the European Union up to 14/01/2022, complemented by hand searches of websites and metasearch engines up to 11/02/2022. We considered the following comparisons: full primary immunization vs. no vaccination, booster immunization vs. no vaccination, and booster vs. full primary immunization. VE against any confirmed SARS-CoV-2 infection, symptomatic, and severe COVID-19 (i.e., COVID-19-related hospitalization, ICU admission, or death) was indicated, providing estimate ranges. Meta-analysis was not performed due to high study heterogeneity. The risk of bias was assessed with ROBINS-I, and the certainty of the evidence was evaluated using GRADE. Results: We identified 26 studies, including 430 to 2.2 million participants, which evaluated VE estimates against infections with the SARS-CoV-2 Omicron variant. VE against any confirmed SARS-CoV-2 infection ranged between 0–62% after full primary immunization and between 34–66% after a booster dose compared to no vaccination. VE range for booster vs. full primary immunization was 34–54.6%. After full primary immunization VE against symptomatic COVID-19 ranged between 6-76%. After booster immunization VE ranged between 3-84% compared to no vaccination and between 56-69% compared to full primary immunization. VE against severe COVID-19 ranged between 3-84% after full primary immunization and between 12-100% after booster immunization compared to no vaccination, and 100% (95% CI 71.4-100) compared to full primary immunization (data from only one study). VE was characterized by a moderate to strong decline within 3–6 months for SARS-CoV-2 infections and symptomatic COVID-19. Against severe COVID-19, protection remained robust for at least up to 6 months. Waning immunity was more profound after primary than booster immunization. The risk of bias was moderate to critical across studies and outcomes. GRADE certainty was very low for all outcomes. Conclusions: Under the Omicron variant, the effectiveness of EU-licensed COVID-19 vaccines in preventing any SARS-CoV-2 infection is low and only short-lasting after full primary immunization, but can be improved by booster vaccination. VE against severe COVID-19 remains high and is long-lasting, especially after receiving the booster vaccination.
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None of the published systematic reviews have assessed the magnitude and duration of protection conferred by booster doses of mRNA vaccines, particularly for the fourth dose, for a comprehensive range of COVID-19 outcomes caused by the Omicron subvariant and its sublineages.
“however, none have assessed the magnitude and duration of protection conferred by booster doses of mRNA vaccines, particularly for the fourth dose, for a comprehensive range of COVID-19 outcomes caused by the Omicron subvariant and its sublineages.”
From Protection of the third-dose and fourth-dose mRNA vaccines against SARS-CoV-2 Omicron subvariant: a systematic review and meta-analysis (2023) · cites this paper as [19]
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Experimental — accuracy not yet measuredPrior evidence has reported robust protection of up to 86% against severe disease caused by the Omicron subvariant after a single dose of mRNA booster, for up to 6 months.
“Similar to our findings, prior evidence has reported robust protection of up to 86% against severe disease caused by the Omicron subvariant after a single dose of mRNA booster, for up to 6 months.18 19 81”
From Protection of the third-dose and fourth-dose mRNA vaccines against SARS-CoV-2 Omicron subvariant: a systematic review and meta-analysis (2023) · cites this paper as [19]
The Results section on severe COVID-19 reports strong protection after booster vaccination, with effectiveness of 78%–93.7% from more than 14 days to 3 months. It says booster data were unavailable for later periods; the 86% figure refers to full primary immunization more than 6 months after vaccination, not a booster. (LLM, conf=0.90)
Experimental — accuracy not yet measuredSeveral systematic reviews of COVID-19 vaccine efficacy and effectiveness, with or without meta-analyses, have been published.
“Several systematic reviews of COVID-19 vaccine efficacy and effectiveness, with or without meta-analyses, have been published11 17–22”
From Protection of the third-dose and fourth-dose mRNA vaccines against SARS-CoV-2 Omicron subvariant: a systematic review and meta-analysis (2023) · cites this paper as [19]
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Sorted by citations
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“protection against infection and symptomatic disease due to Omicron [7,8].”
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“…the VE of third-dose and fourth-dose mRNA vaccines against SARS- CoV-2 Omicron subvariant infection and symptomatic infection wanes over time; however, it offers substantial protection for at least 6 months against severe COVID-19 outcomes, although the duration of protection remains uncertain.”
Background
- Authors
- Külper-Schiek, W., Piechotta, V., Pilic, A., Batke, M., Dreveton, L.-S., Geurts, B., Koch, J., Köppe, S., Treskova, M., Vygen-Bonnet, S., Waize, M., Wichmann, O., & Harder, T.
- Affiliations
- Robert Koch Institute (DE)
- Corresponding author
- Piechotta, Vanessa
- ORCID
- Venue
- Frontiers in Immunology
- Publisher
- Frontiers Media SA
- Published
- 2022-08-24
- Volume
- 13
- Pages
- 940562-940562
- ISSN
- 1664-3224 (ISSN-L)
- PMC
- PMC9449804
- OpenAlex
- W4293113133
- Cited by
- 44
- References
- 22
- Citations by year
- 2026: 2 · 2025: 4 · 2024: 13 · 2023: 21 · 2022: 4
- FWCI
- 1.61
- Type
- journal article
- Language
- en
- Open access
- gold
- doi.org
- Licence
- Locations
- Frontiers in Immunology (publishedVersion, cc-by)
- medRxiv (acceptedVersion, cc-by-nc-nd)
- PubMed Central (publishedVersion, cc-by)
- PubMed (publishedVersion)
- DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
- Publication server of the Robert Koch Institute (Robert Kock Institute) (submittedVersion, cc-by)
- Topics
- Health Sciences › Medicine › Infectious Diseases › SARS-CoV-2 and COVID-19 Research
- Physical Sciences › Mathematics › Modeling and Simulation › COVID-19 epidemiological studies
- Social Sciences › Health › Vaccine Coverage and Hesitancy
- Keywords
- Omicron variant, COVID-19 vaccines, vaccine effectiveness, booster vaccination, basic immunization, duration of protection, symptomatic COVID-19, severe COVID-19, SARS-CoV-2, hospitalization, intensive care unit admission, vaccine safety, adverse events
- MeSH terms
- COVID-19, SARS-CoV-2, COVID-19 Vaccines, Humans, Influenza Vaccines
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