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Risk of COVID-19 after natural infection or vaccination
Journal article   Open access   Peer reviewed

Risk of COVID-19 after natural infection or vaccination

Anne-Marie Rick, Matthew B. Laurens, Ying Huang, Chenchen Yu, Thomas C.S. Martin, Carina A. Rodriguez, Christina A. Rostad, Rebone M. Maboa, Lindsey R. Baden, Hana M. El Sahly, …
EBioMedicine, Vol.96, 104799
10/2023
DOI: 10.1016/j.ebiom.2023.104799
PMCID: PMC10518569
PMID: 37738833
url
https://doi.org/10.1016/j.ebiom.2023.104799View
Published (Version of record) Open Access

Abstract

While vaccines have established utility against COVID-19, phase 3 efficacy studies have generally not comprehensively evaluated protection provided by previous infection or hybrid immunity (previous infection plus vaccination). Individual patient data from US government-supported harmonized vaccine trials provide an unprecedented sample population to address this issue. We characterized the protective efficacy of previous SARS-CoV-2 infection and hybrid immunity against COVID-19 early in the pandemic over three-to six-month follow-up and compared with vaccine-associated protection. In this post-hoc cross-protocol analysis of the Moderna, AstraZeneca, Janssen, and Novavax COVID-19 vaccine clinical trials, we allocated participants into four groups based on previous-infection status at enrolment and treatment: no previous infection/placebo; previous infection/placebo; no previous infection/vaccine; and previous infection/vaccine. The main outcome was RT-PCR-confirmed COVID-19 >7–15 days (per original protocols) after final study injection. We calculated crude and adjusted efficacy measures. Previous infection/placebo participants had a 92% decreased risk of future COVID-19 compared to no previous infection/placebo participants (overall hazard ratio [HR] ratio: 0.08; 95% CI: 0.05–0.13). Among single-dose Janssen participants, hybrid immunity conferred greater protection than vaccine alone (HR: 0.03; 95% CI: 0.01–0.10). Too few infections were observed to draw statistical inferences comparing hybrid immunity to vaccine alone for other trials. Vaccination, previous infection, and hybrid immunity all provided near-complete protection against severe disease. Previous infection, any hybrid immunity, and two-dose vaccination all provided substantial protection against symptomatic and severe COVID-19 through the early Delta period. Thus, as a surrogate for natural infection, vaccination remains the safest approach to protection. National Institutes of Health.
COVID-19 Hybrid immunity Natural infection Vaccination

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