Household serial interval of COVID-19 and the effect of Variant B.1.1.7: analyses from prospective community cohort study (Virus Watch) [version 2; peer review: 2 approved]
Introduction: Increased transmissibility of B.1.1.7 variant of concern
(VOC) in the UK may explain its rapid emergence and global spread.
We analysed data from putative household infector - infectee pairs in
the Virus Watch Community cohort study to assess the serial interval
of COVID-19 and whether this was affected by emergence of the
B.1.1.7 variant. /
Methods: The Virus Watch study is an online, prospective, community
cohort study following up entire households in England and Wales
during the COVID-19 pandemic. Putative household infector-infectee
pairs were identified where more than one person in the household
had a positive swab matched to an illness episode. Data on whether or
not individual infections were caused by the B.1.1.7 variant were not
available. We therefore developed a classification system based on the
percentage of cases estimated to be due to B.1.1.7 in national
surveillance data for different English regions and study weeks. /
Results: Out of 24,887 illnesses reported, 915 tested positive for SARSCoV-2 and 186 likely ‘infector-infectee’ pairs in 186 households
amongst 372 individuals were identified. The mean COVID-19 serial
interval was 3.18 (95%CI: 2.55 - 3.81) days. There was no significant
difference (p=0.267) between the mean serial interval for VOC
hotspots (mean = 3.64 days, (95%CI: 2.55 – 4.73)) days and non-VOC
hotspots, (mean = 2.72 days, (95%CI: 1.48 – 3.96))