MOSCOW, 10 Jan. Danish scientists published in The Journal of Infectious Diseases the results of the first study comparing the risk of infection and clinical outcomes of COVID-19 among vaccinated and unvaccinated against influenza. The study involved more than 46,000 healthcare workers in Denmark. Previous laboratory studies analyzing the immune responses of patients with COVID-19 showed that the flu vaccine may provide some protection against the coronavirus. However, some scientists have raised concerns that a flu shot could raise the risk of SARS-CoV-2 infection or worsen the severity of the disease. Danish scientists led by Jonas Henrik Kristensen M.D. from the University Hospital of Copenhagen decided to check. Does influenza vaccination affect the risk of COVID-19 infection? The authors processed data from 46 112 health workers in the Copenhagen metropolitan region and the Zeeland region, who were tested for antibodies to SARS-CoV-2 three times during 2020, and for which information was available about influenza vaccination. Among them, 3379 people have had COVID-19 with obvious symptoms or were hospitalized. 
Crimean scientists have created a unique flu vaccine comorbidities, scientists have found that the risk ratio of contracting coronavirus infection in vaccinated against influenza is 0.93-1.01 compared to unvaccinated participants. The risks of symptomatic course and hospitalization are 1.02-1.03 and 0.89-0.91, respectively. In a subgroup of 1,841 participants over 65 years of age, the risk of infection for vaccinated people was 0.93-0.99 compared to unvaccinated ones, and the risk of hospitalization was at the level of unity. Hence, the authors conclude that influenza vaccination does not affect the risk of SARS infection. CoV-2 or COVID-19 disease severity. These results coincide with the results of previous work based on PCR testing data or serological studies.
