According to a nationwide study in Sweden, people who received a first dose of the Oxford-Astrazeneca Covid-19 vaccine followed by an mRNA vaccine shot had a lower risk of getting infected, compared to those immunised as compared to the two doses of AstraZeneca preventive. As AstraZeneca’s vector-based vaccine was halted for people younger than 65 years of age due to safety concerns, all individuals in Sweden who had already received their first dose of this vaccine were recommended an mRNA vaccine as their second dose.
The study, published in The Lancet Regional Health-Europe journal is based on the Public Health Agency of Sweden’s nationwide registry data, the National Board of Health and Welfare, and Statistics Sweden.
Around 7,00,000 individuals were included in the main analysis. During a 2.5-month average follow-up period after the second dose, the study showed a 67% lower risk of infection for the combination of AstraZeneca and Pfizer vaccine shots.
For the AstraZeneca and Moderna vaccine shots, there was a 79% lower risk of infection as compared to unvaccinated individuals, according to the researchers.
They said that the risk reduction was 50 for people having received two doses of the AstraZeneca vaccine which is known as Covishield in India.
The estimates for risk were observed after accounting for differences regarding date of vaccination, age of the participants, socioeconomic status, and other risk factors for Covid-19.
It was also noted by researchers that the study estimates of effectiveness apply to the delta variant of Covid, which was dominating the confirmed cases during the follow-up period.