NEJM Published online 19 May, 2021 | https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(21)00676-0/fulltext
Digest author(s): Stylianos Loukides, e-Learning Director / 23 May 2021
Nursing homes were highly affected by the SARS COV2 infection with increased mortality among the residents. Vaccines were introduced in mid of December 2020 to protect people from COVID-19 infection and particularly the severe one. In the current study using medical records the authors wanted to determine the incidence of SARS-CoV-2 infection among vaccinated residents and unvaccinated residents of 280 nursing homes across 21 states in the USA.
The study included a total of 18,242 people who had received at least one dose of the vaccine; 14,669 (80.4%) the Pfizer vaccine and 3,573 (19.6%) the Moderna vaccine. Of these, 13,048 had received the second dose of the vaccine. 3,990 people had not been vaccinated. The incidence of infection gradually decreased in both vaccinated and unvaccinated individuals. 822 cases (4.5%) were counted after the first dose of the vaccine from day 0 to day 14 from vaccination and 250 (1.4%) from day 15 to day 28. Of the fully vaccinated, 130 cases (1%) were described from day 0 to day 14 of the second dose and 38 (0.3%) after the 14th day. Among the unvaccinated, 173 cases (4.3%) were described up to 14 days after the start of vaccinations and 12 cases (0.3%) after 42 days. Based on these data, across all the study groups, most infections were asymptomatic, and the incidence of both asymptomatic and symptomatic infections decreased. It has also been shown that mass vaccination and precautionary measures such as the use of a mask can to some extent protect small groups of unvaccinated individuals.
In a high risk population–that of Nursing homes–mass vaccination significantly decreased the rate of infections by establishing a strong immunity. Interestingly, the above approach significantly affected the rate of infections in unvaccinated people. The above observation had two important messages. The first is that vaccination clearly prohibits the dispersion of trans-infection. Furthermore, in a wide spectrum of population involving unvaccinated people, vaccines may alter not only the rate of infections but also the clinical severity.