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. 2024 Jun 18:36:100824.
doi: 10.1016/j.lana.2024.100824. eCollection 2024 Aug.

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

Lara E Coelho  1 , Paula M Luz  1 , Débora C Pires  1 , Emilia M Jalil  1 , Hugo Perazzo  1 , Thiago S Torres  1 , Sandra W Cardoso  1 , Eduardo M Peixoto  1 , Sandro Nazer  1 , Eduardo Massad  2 , Luiz Max Carvalho  2   3 , Weeberb J Réquia  4 , Fernando Couto Motta  5 , Marilda Mendonça Siqueira  5 , Ana T R Vasconcelos  6 , Guilherme C da Fonseca  6 , Liliane T F Cavalcante  6 , Carlos A M Costa  7 , Rodrigo T Amancio  8 , Daniel A M Villela  9   10 , Tiago Pereira  3 , Guilherme T Goedert  2 , Cleber V B D Santos  11 , Nadia C P Rodrigues  7   11 , Breno Augusto Bormann de Souza Filho  7   12 , Daniel Csillag  2 , Beatriz Grinsztejn  1 , Valdilea G Veloso  1 , Claudio J Struchiner  2   11
Affiliations

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

Lara E Coelho et al. Lancet Reg Health Am. .

Abstract

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.

Keywords: Brazil; COVID-19; Household transmission; Social inequity; Transmission dynamics.

PubMed Disclaimer

Conflict of interest statement

CJS is a member of PAHO and WHO advisory boards (no payment involved). All other authors declare that they have no competing interests.

Figures

Fig. 1
Fig. 1
Spatial distribution of the human development index (HDI, panel A) and population density (inhabitants per square kilometre, panel B) across Rio de Janeiro's neighbourhoods with Manguinhos highlighted in black, according to the 2010 census.
Fig. 2
Fig. 2
Panel A: Number of confirmed COVID-19 cases per day, relative frequency of SARS-CoV-2 variants of interest (VOI) and COVID-19 vaccine coverage (2 doses) in Rio de Janeiro city over time. Panel B: Number of households enrolled per day in the Comvida-2 study over time.
Fig. 3
Fig. 3
Panel A: Estimated median of the posterior distribution of the extra-household and within-household infection probability (dot) and 95% credible interval (bar) by age and gender. Panel B: Estimated median of the posterior distribution of the extra-household and within-household infection probability (dot) and 95% credible interval (bar) by age and household density (persons per bedroom).
Fig. 4
Fig. 4
Panel A: Estimated median of the posterior distribution of the extra-household and within-household infection probability (dot) and 95% credible interval (bar) by age and employment status. Panel B: Estimated median of the posterior distribution of the extra-household and within-household infection probability (dot) and 95% credible interval (bar) by age and monthly family income categorized according to the number minimum wages. Panel C: Estimated median of the posterior distribution of the extra-household and within-household infection probability (dot) and 95% credible interval (bar) by age and receipt of the cash transfer program Bolsa Familia. Panel D: Estimated median of the posterior distribution of the extra-household and within-household infection probability (dot) and 95% credible interval (bar) by age and receipt of the cash transfer program Auxílio Financeiro Emergencial.
Fig. 5
Fig. 5
Panel A: Estimated median of the posterior distribution of the extra-household and within-household infection probability (dot) and 95% credible interval (bar) by age and reported means of transportation. Panel B: Estimated median of the posterior distribution of the extra-household and within-household infection probability (dot) and 95% credible interval (bar) by age and reported adherence to social distancing measures. Panel C: Estimated median of the posterior distribution of the extra-household and within-household infection probability (dot) and 95% credible interval (bar) by age and reported frequency of leaving one's house.
Fig. 6
Fig. 6
Estimated median of the posterior distribution of the extra-household and within-household infection probability (dot) and 95% credible interval (bar) by age and reported receipt of COVID-19 vaccine doses.
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