The Lancet Regional Health. Americas (Aug 2024)

SARS-CoV-2 transmission in a highly vulnerable population of Brazil: a household cohort studyResearch in context

  • Lara E. Coelho,
  • Paula M. Luz,
  • Débora C. Pires,
  • Emilia M. Jalil,
  • Hugo Perazzo,
  • Thiago S. Torres,
  • Sandra W. Cardoso,
  • Eduardo M. Peixoto,
  • Sandro Nazer,
  • Eduardo Massad,
  • Luiz Max Carvalho,
  • Weeberb J. Réquia,
  • Fernando Couto Motta,
  • Marilda Mendonça Siqueira,
  • Ana T.R. Vasconcelos,
  • Guilherme C. da Fonseca,
  • Liliane T.F. Cavalcante,
  • Carlos A.M. Costa,
  • Rodrigo T. Amancio,
  • Daniel A.M. Villela,
  • Tiago Pereira,
  • Guilherme T. Goedert,
  • Cleber V.B.D. Santos,
  • Nadia C.P. Rodrigues,
  • Breno Augusto Bormann de Souza Filho,
  • Daniel Csillag,
  • Beatriz Grinsztejn,
  • Valdilea G. Veloso,
  • Claudio J. Struchiner

Journal volume & issue
Vol. 36
p. 100824

Abstract

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Summary: Background: Household transmission studies seek to understand the transmission dynamics of a pathogen by estimating the risk of infection from household contacts and community exposures. We estimated within/extra-household SARS-CoV-2 infection risk and associated factors in a household cohort study in one of the most vulnerable neighbourhoods in Rio de Janeiro city. Methods: Individuals ≥1 years-old with suspected or confirmed COVID-19 in the past 30 days (index cases) and household members aged ≥1 year were enrolled and followed at 14 and 28 days (study period November/2020–December/2021). RT-PCR testing, COVID-19 symptoms, and SARS-CoV-2 serologies were ascertained in all visits. Chain binomial household transmission models were fitted using data from 2024 individuals (593 households). Findings: Extra-household infection risk was 74.2% (95% credible interval [CrI] 70.3–77.8), while within-household infection risk was 11.4% (95% CrI 5.7–17.2). Participants reporting having received two doses of a COVID-19 vaccine had lower extra-household (68.9%, 95% CrI 57.3–77.6) and within-household (4.1%, 95% CrI 0.4–16.6) infection risk. Within-household infection risk was higher among participants aged 10–19 years, from overcrowded households, and with low family income. Contrastingly, extra-household infection risk was higher among participants aged 20–29 years, unemployed, and public transportation users. Interpretation: Our study provides important insights into COVID-19 household/community transmission in a vulnerable population that resided in overcrowded households and who struggled to adhere to lockdown policies and social distancing measures. The high extra-household infection risk highlights the extreme social vulnerability of this population. Prioritising vaccination of the most socially vulnerable could protect these individuals and reduce widespread community transmission. Funding: Fundação Oswaldo Cruz, CNPq, FAPERJ, Royal Society, Instituto Serrapilheira, FAPESP.

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