Inferring risks of coronavirus transmission from community household data

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 COVID-19 Infection Survey 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 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 of 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.

Automated summary

This study analyzes the data from the Office for National Statistics COVID-19 Infection Survey in England, focusing on household infection and transmission. The findings indicate that the rate of infection introduction into households varies over time in line with the overall epidemic and vaccination program. The susceptible-infectious transmission probabilities within households range from 15% to 35%. The emergence of the Alpha and Delta variants has influenced the infectiousness within households, with the Alpha variant being around 50% more infectious than the wildtype and 35% less infectious than the Delta variant. Additionally, workers in patient-facing roles had a significantly higher risk (ranging from 25% to 300%) of bringing infection into their households prior to vaccination. There is also an increased risk for secondary school-age children to bring infection into their households when schools are open, as well as for primary school-age children since the emergence of new variants.