LONDON: The people who received the first dose of the Oxford-Astrazeneca vaccine (AZ) Covid-19 were followed by MRNA vaccine shots had a lower risk of infection than those who were immunized with the two preventive doses of AZ, according to a national study in Sweden.
Because the use of vector-based vaccines is stopped for people who are younger than 65 years due to security issues, all individuals in Sweden who have received their first dose of this vaccine recommended the MRNA vaccine as their second dose.
“…
our study shows a greater risk reduction for people who receive the MRNA vaccine after receiving a vector-based first dose, compared to people who receive vector-based vaccines for both doses,” said Peter Nordstrom from Umeå University.
This study was published in the Regional Health Lancet – Europe Journal on Monday.
In the main analysis, around 7.00,000 individuals are included.
During the follow-up period an average of 2.5 months after the second dose, the study showed the risk of infection 67% lower for the combination of AZ and Pfizer shots.
There is a risk of 79% lower infection for AZ and modernary shots, compared to individuals who are not vaccinated, the researchers said.
For people having two doses of AZ vaccines (covishield in India), risk reduction is 50%, they said.
The researchers noted that the estimated effectiveness research applies to infection with the Delta variant, which dominated the cases confirmed during follow-up.
“The results of the study may have implications for vaccination strategies in various countries,” said Marcel Ballin, a doctoral student at the University of Umeå, and co-authors study.
There is a very low incident of thromboembolism, or blood clots in blood vessels.