ArticleClinical infectious diseases : an official publication of the Infectious Diseases Society of America2025
Incidence of and Risk Factors for SARS-CoV-2 Infection Among Vaccinated Healthcare Workers During Emergence of SARS-CoV-2 Gamma Variant in the Amazon Region, Brazil, 2021.
Article in Clinical infectious diseases : an official publication of the Infectious Diseases Society of America, 2025. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Not yet cited in PubMed.
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Abstract
backgroundThe emergence of new severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants poses a significant threat to public health and healthcare workers (HCWs). The SARS-CoV-2 Gamma variant emerged in Manaus, Brazil, in December 2020, leading to a large wave of infections and deaths.
methodsWe conducted a prospective cohort study among HCWs at 2 hospitals in Manaus from 31 March to 31 May 2021. HCWs were followed up for 3 weeks with nasal swabs collected at baseline and weekly (total: 4 visits), regardless of symptoms, for SARS-CoV-2 testing. Blood samples were collected for SARS-CoV-2 serology at baseline. Staff collected data on symptoms, healthcare, and community exposures, and vaccination status at each visit. We evaluated coronavirus disease 2019 (COVID-19) attack rate, risk factors for disease, and differences in rates by vaccination status.
resultsWe included 771 HCWs (388 and 383 per hospital). The median age was 40 years (IQR: 31-48), 600 (77.8%) were female, 449 (58.2%) were nurses, and 568 (73.6%) were fully vaccinated at enrollment. We identified 16 SARS-CoV-2 incident infections for an overall attack rate of 5.2 per 1000 HCW-weeks. Of the 16 infected HCWs, 12 were fully vaccinated (attack rate: 5.2/1000 HCW-weeks vs 5.9/1000 HCW-weeks among unvaccinated). All 12 vaccinated HCWs tested negative after 1-week follow-up, while 2 of the 3 infected unvaccinated individuals remained positive at follow-up (P < .05).
conclusionsThe COVID-19 attack rate among this cohort of HCWs with high vaccine coverage was low. Among vaccinated HCWs who tested positive, none tested positive after 1 week, indicating more rapid viral clearance vs unvaccinated HCWs. HCW vaccination is an important measure for HCW safety and more resilient healthcare systems.
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