A study2 of covid-19 transmission within English households using data gathered in early 2021 found that even a single dose of a covid-19 vaccine reduced the likelihood of household transmission by 40-50%. This was supported by a study of household transmission among Scottish healthcare workers conducted between December 2020 and March 2021.3 Both studies analysed the impact of vaccination on transmission of the α variant of SARS-CoV-2, which was dominant at the time.