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. 2022 May;37(5):549-561.
doi: 10.1007/s10654-022-00870-9. Epub 2022 May 28.

Transmission of SARS-CoV-2 within households: a remote prospective cohort study in European countries

Janneke D M Verberk #  1   2 , Marieke L A de Hoog #  3 , Ilse Westerhof  1 , Sam van Goethem  4 , Christine Lammens  4 , Greet Ieven  4 , Erwin de Bruin  5 , Dirk Eggink  6 , Julia A Bielicki  7 , Samuel Coenen  4 , Janko van Beek  5 , Marc J M Bonten  1 , Herman Goossens  4 , Patricia C J L Bruijning-Verhagen  1
Affiliations

Transmission of SARS-CoV-2 within households: a remote prospective cohort study in European countries

Janneke D M Verberk et al. Eur J Epidemiol. 2022 May.

Abstract

Household transmission studies are useful to quantify SARS-CoV-2 transmission dynamics. We conducted a remote prospective household study to quantify transmission, and the effects of subject characteristics, household characteristics, and implemented infection control measures on transmission. Households with a laboratory-confirmed SARS-CoV-2 index case were enrolled < 48 h following test result. Follow-up included digitally daily symptom recording, regular nose-throat self-sampling and paired dried blood spots from all household members. Samples were tested for virus detection and SARS-CoV-2 antibodies. Secondary attack rates (SARs) and associated factors were estimated using logistic regression. In 276 households with 920 participants (276 index cases and 644 household members) daily symptom diaries and questionnaires were completed by 95%, and > 85% completed sample collection. 200 secondary SARS-CoV-2 infections were detected, yielding a household SAR of 45.7% (95% CI 39.7-51.7%) and per-person SAR of 32.6% (95%CI: 28.1-37.4%). 126 (63%) secondary cases were detected at enrollment. Mild (aRR = 0.57) and asymptomatic index cases (aRR = 0.29) were less likely to transmit SARS-CoV-2, compared to index cases with an acute respiratory illness (p = 0.03 for trend), and child index cases (< 12 years aRR = 0.60 and 12-18 years aRR = 0.85) compared to adults (p = 0.03 for trend). Infection control interventions in households had no significant effect on transmission. We found high SARs with the majority of transmissions occuring early after SARS-CoV-2 introduction into the household. This may explain the futile effect of implemented household measures. Age and symptom status of the index case influence secondary transmission. Remote, digitally-supported study designs with self-sampling are feasible for studying transmission under pandemic restrictions.

Keywords: COVID-19 (household) transmission; Epidemiology; SARS-CoV-2.

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Conflict of interest statement

The authors have no relevant financial or non-financial interests to disclose.

Figures

Fig. 1
Fig. 1
Flow diagram of the study population
Fig. 2
Fig. 2
Timing of SARS-CoV-2 positivity (in blue) and symptom onset (in orange) of the secondary cases over time (n = 200). *Of the 21 secondary cases with no symptoms 11 (52.4%) were detected by a positive PCR at enrollment and 10 (47.6%) by seroconversion only
See this image and copyright information in PMC

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