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Comparative COVID-19 Vaccines Effectiveness in Preventing Infections, Hospitalizations, and Deaths with SARS-CoV-2 BA.5 and Ba.2 Omicron Lineages: A Case-Case and Cohort Study Using Electronic Health Records in Portugal
16 Pages Posted: 3 Aug 2022More...
Background: In the context of a highly vaccinated population and multiple Omicron lineages circulation, it is relevant to clarify the effect of vaccination and previous infections on the risk of infection and severe post-infection outcomes. This study aimed to measure the comparative vaccine effectiveness of primary and booster vaccination between Omicron BA.5 and BA.2 lineages against infection and compare lineage-specific post-infection vaccine effectiveness against COVID-19-related hospitalization and mortality.
Methods: Using electronic health records and SARS-CoV-2 laboratory surveillance data, we conducted a case-case and a cohort study covering the period of Omicron BA.2/BA.5 lineage replacement in Portugal (April 25 and June 10, 2022). Variant classification was performed through whole-genome sequencing or Spike Gene Target Failure.
Findings: From a total of 27,702 samples, 55.5% were classified as BA.2 and the remaining as BA.5. We observed no evidence of reduced vaccine effectiveness from either the primary vaccination (OR=1.07, 95%CI:0.93-1.23) or booster dose (OR=0.96, 95%CI:0.84-1.09) against BA.5 infection compared with BA.2. Higher odds of previous infection were observed in BA.5 cases compared with BA.2 (OR=1.44; 95%CI:1.30-1.60). Among those infected with BA.5, booster post-infection vaccine effectiveness was 77% (95%CI:49-90%) and 88% (95%CI:70-96%) against COVID-19 hospitalization and death, respectively, while among BA.2 cases, booster post-infection vaccine effectiveness was 93% (95%CI:86-97%) and 94% (95%CI:76-99%), respectively.
Interpretation: This study shows that the SARS-CoV-2 Omicron BA.5 lineage was associated with higher odds of previous infection compared with Omicron BA.2. Although less effective compared with BA.2, COVID-19 booster vaccination still offers substantial post-infection protection against severe outcomes following BA.5 infection.
Funding Information: The acquisition of sequencing equipment/reagents used in this study by INSA was partially funded by the HERA project (Grant/2021/PHF/23776) supported by the European Commission through the European Centre for Disease Control, and also partially funded by the GenomePT project (POCI-01-0145-FEDER-022184), supported by COMPETE 2020 – Operational Programme for Competitiveness and Internationalisation (POCI), Lisboa Portugal Regional Operational Programme (Lisboa2020), Algarve Portugal Regional Operational Programme (CRESC Algarve2020), under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund (ERDF), and by the Portuguese Science and Technology Foundation (FCT).
Declaration of Interests: None.
Ethics Approval Statement: The genomic surveillance of SARS-CoV-2 in Portugal is regulated by the Assistant Secretary of State and Health Executive Order (Despacho n. º 331/2021 of January 11, 2021). The study protocol received the clearance of the Ethics Committee of INSA on June 15, 2022.
Keywords: COVID-19, relative vaccine effectiveness, post-infection vaccine effectiveness, BA5, BA2
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