Researchers from Sweden have shown that people who received a combination of doses of AstraZeneca and mRNA vaccines had a lower risk of coronavirus infection than those who received two doses of the vector vaccine. The researchers from Umea University published the article in The Lancet Regional Health - Europe.
The average follow-up period of more than 700,000 participants was 2.5 months. During this time the risk of infection in 94 thousand people who received a combination of AstraZeneca and Pfizer vaccines decreased by 67 percent, and in those 16 thousand who received the second dose of Moderna - by 79 percent. A total of 187 of that number contracted the coronavirus infection. The average effectiveness for both vaccines was 68 percent. In 430 thousand people who received two doses of AstraZeneca the figure was 50 percent.
The researchers emphasize that they took all COVID-19 risk factors into account in evaluating efficacy. Importantly, they note, the efficacy of the combinations also extends to the "delta" variant of SARS-CoV-2, which is what most study participants were infected with. Cases of thromboembolic complications for all combinations were extremely rare, the experts emphasize.
Earlier, a number of European countries suspended vaccination with AstraZeneca for people over 65 years of age due to the detection of thrombosis in vaccinated patients. All those who had already received the first dose of the vector vaccine were advised to receive a second dose of mRNA vaccines.