Inferring Risks of Coronavirus Transmission from Community Household Data

TL;DR

This study analyzes household transmission risks of COVID-19 in England, revealing how infection rates vary over time, differ by variants, and are influenced by occupation and school attendance, informing targeted control measures.

Contribution

It provides detailed estimates of household transmission probabilities, variant-specific infectiousness, and the impact of occupation and school opening on infection risk, using extensive survey data.

Findings

Within-household transmission probability ranges from 15-35%.

Alpha variant is ~50% more infectious than wildtype.

Increased infection risk for workers in patient-facing roles and school-aged children.

Abstract

The response of many governments to the COVID-19 pandemic has involved measures to control within- and between-household transmission, providing motivation to improve understanding of the absolute and relative risks in these contexts. Here, we perform exploratory, residual-based, and transmission-dynamic household analysis of the Office for National Statistics (ONS) COVID-19 Infection Survey (CIS) data from 26 April 2020 to 15 July 2021 in England. This provides evidence for: (i) temporally varying rates of introduction of infection into households broadly following the trajectory of the overall epidemic and vaccination programme; (ii) Susceptible-Infectious Transmission Probabilities (SITPs) of within-household transmission in the 15-35% range; (iii) the emergence of the Alpha and Delta variants, with the former being around 50% more infectious than wildtype and 35% less infectious than Delta within households; (iv) significantly (in the range 25-300%) more risk of bringing infection into the household for workers in patient-facing roles pre-vaccine; (v) increased risk for secondary school-age children of bringing the infection into the household when schools are open; (vi) increased risk for primary school-age children of bringing the infection into the household when schools were open since the emergence of new variants.