Case series/case reports (Indigo)
Whether vaccination of individual persons for SARS-CoV-2 protects members of their households is unclear. In this study the authors investigated the effect of vaccination of health care workers in Scotland on the risk of coronavirus disease 2019 (COVID-19) among members of their households.
Data from 194,362 household members (which represented 92,470 households of 2 to 14 persons per household) of 144,525 health care workers who had been employed during the period from March 2020 through November 2020 were evaluated. A total of 113,253 health care workers (78.4%) had received at least one dose of either the BNT162b2 (Pfizer–BioNTech) mRNA vaccine or the ChAdOx1 nCoV-19 (Oxford–AstraZeneca) vaccine, and 36,227 (25.1%) had received a second dose. The primary outcome was any confirmed case of COVID-19 that occurred between December 8, 2020, and March 3, 2021. Cases of COVID-19 were less common among household members of vaccinated health care workers during the period beginning 14 days after the first dose than during the unvaccinated period before the first dose (event rate per 100 person-years, 9.40 before the first dose and 5.93 beginning 14 days after the first dose). After the health care worker’s second dose, the rate in household members was lower still (2.98 cases per 100 person-years). These differences persisted after fitting extended Cox models that were adjusted for calendar time, geographic region, age, sex, occupational and socioeconomic factors, and underlying conditions. Relative to the period before each health care worker was vaccinated, the hazard ratio for a household member to become infected was 0.70 (95% confidence interval [CI], 0.63 to 0.78) for the period beginning 14 days after the first dose and 0.46 (95% CI, 0.30 to 0.70) for the period beginning 14 days after the second dose. The authors concluded that they provide empirical evidence suggesting that vaccination may reduce transmission by showing that vaccination of health care workers is associated with a decrease in documented cases of COVID-19 among members of their households. This finding is reassuring for health care workers and their families.
Shah ASV, Gribben C, Bishop J, Hanlon P, Caldwell D, Wood R, Reid M, McMenamin J, Goldberg D, Stockton D, Hutchinson S, Robertson C, McKeigue PM, Colhoun HM, McAllister DA. Effect of Vaccination on Transmission of SARS-CoV-2. N Engl J Med. 2021 Sep 8. doi: 10.1056/NEJMc2106757.