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Published: June 18, 2024
DOI: https://doi.org/10.1016/j.lana.2024.100824
Lara E. Coelho, Paula M. Luz, Débora C. Pires, Emilia M. Jalil, Hugo Perazzo, Thiago S. Torres, et al.
Summary
Background
Household transmission studies seek to understand the transmission dynamics of a pathogen by esti- mating 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.
