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The "New England Journal of Medicine" published the results of research on the effectiveness of vaccines against COVID-19. Researchers compared the degree of protection provided by three formulations - Pfizer, Moderna and Johnson & Johnson - over two and seven months after vaccination. What did they find?
The research was conducted by scientists from the University of North Carolina in Chapel Hill in the USA. They compared the effectiveness of three vaccines against COVID-19: two-dose preparations of Pfizer / BioNTech (BNT162b2) and Moderna (mRNA-1273) and the single-dose vaccine of Johnson & Johnson (Ad26.COV2.S). The Astra Zeneca vaccine was not included in the list as it is not used in the US.
Researchers analyzed nine-month COVID-19 vaccination and disease data (December 11, 2022 to September 8, 2022) for approximately 10.6 million North Carolina residents. The data was collected from two systems: the COVID-19 surveillance system in North Carolina and the COVID-19 vaccine management system.
Then using the so-called Cox regression model estimated the effectiveness of vaccines in reducing the risk of COVID-19 infection, hospitalization, and death as a function of the time since vaccination.
What results did they get?
For the Pfizer and Moderna vaccines, the effectiveness against COVID-19 was 94.5%, respectively. and 95.9 percent two months after vaccination. After seven months, this effectiveness decreased to 66.6%. for Pfizer and 80.3 percent. for Moderna. In the case of the single-dose vaccine (Johnson & Johnson), the effectiveness against COVID-19 was 74.8%. a month after its administration and decreased to 59.4 percent. after five months
According to experts, such a significant decrease in protection against infection can be explained by the appearance of new variants of the coronavirus. The researchers emphasized that all three vaccines were more effective over time in preventing hospitalization and death than in preventing infection.