Behavioral factors and SARS-CoV-2 transmission heterogeneity within a household cohort in Costa Rica

Abstract

Introduction Variability in household secondary attack rates and transmission risks factors of SARS-CoV-2 remain poorly understood. Methods We conducted a household transmission study of SARS-CoV-2 in Costa Rica, with SARS-CoV-2 index cases selected from a larger prospective cohort study and their household contacts were enrolled. A total of 719 household contacts of 304 household index cases were enrolled from November 21, 2020, through July 31, 2021. Blood specimens were collected from contacts within 30–60 days of index case diagnosis; and serum was tested for presence of spike and nucleocapsid SARS-CoV-2 IgG antibodies. Evidence of SARS-CoV-2 prior infections among household contacts was defined based on the presence of both spike and nucleocapsid antibodies. We fitted a chain binomial model to the serologic data, to account for exogenous community infection risk and potential multi-generational transmissions within the household. Results Overall seroprevalence was 53% (95% confidence interval (CI) 48–58%) among household contacts. The estimated household secondary attack rate is 34% (95% CI 5–75%). Mask wearing by the index case is associated with the household transmission risk reduction by 67% (adjusted odds ratio = 0.33 with 95% CI: 0.09–0.75) and not sharing bedroom with the index case is associated with the risk reduction of household transmission by 78% (adjusted odds ratio = 0.22 with 95% CI 0.10–0.41). The estimated distribution of household secondary attack rates is highly heterogeneous across index cases, with 30% of index cases being the source for 80% of secondary cases. Conclusions Modeling analysis suggests that behavioral factors are important drivers of the observed SARS-CoV-2 transmission heterogeneity within the household.

Cohort profile: evaluation of immune response and household transmission of SARS-CoV-2 in Costa Rica: the RESPIRA study

“…The results of the household transmission study have been published. 18 We detected a seroprevalence of 53% among household members of our index cases, with an estimated household secondary attack rate of 34%. Mask wearing by the index cases was strongly protective against transmission to the household.…”

“…Characteristics or behaviour of the index cases were considered determinants of transmission, while characteristics of the household members were considered determinants of susceptibility. The results of the household transmission study have been published 18…”

Age-Specific All-Cause Mortality Disparities by Race and Ethnicity During the COVID-19 Pandemic

“…26 For example, policies providing appropriate and cost-free isolation for essential workers would have prevented chains of Covid-19 transmission to higher-risk people who resided in multi-generation households, especially during pre-vaccine and pre-therapeutic eras. [27][28][29] Similarly, efforts to increase vaccination uptake and implement effective therapeutics among at-risk populations would have reduced disparities. 23,[30][31][32][33][34][35][36] For the overall population and among all adults (>25 years), existing race/ethnicity mortality disparities widened at the onset of the pandemic and during Covid-19 waves but narrowed during the vaccine era.…”

Concordance between SARS-CoV-2 index individuals and their household contacts on index individual COVID-19 transmission cofactors: a comparison of self-reported and contact-reported information

“…Previous COVID-19 transmission studies have shown that sharing a bedroom with the index individual significantly increases transmission risk, while self-reported mask wearing by contacts or the index individual significantly decreases transmission risk [ 8 , 9 ]. In a PEP study, differences in household demographics, the severity of an index individual’s illness, and their interactions with household members can lead to very different risks of transmission within the household.…”

“…Although studies primarily assessing COVID-19 transmission often enroll both the index individuals and their contacts [ 6 , 7 ], to our knowledge no studies assessing COVID-19 PEP have enrolled index individuals because they do not directly inform the efficacy of prevention interventions. However, the severity of an index individual’s illness and their interaction with household members are important predictors of infection in their household contacts [ 8 , 9 ], and adjusting for prognostic covariates such as these can increase the precision of PEP efficacy estimates [ 10 ].…”