Lancet study suggests mix-and-match of COVID vaccines reduce risk of infection

The latest research which is conducted throughout Sweden revealed that people who got the first dosage of Oxford-AstraZeneca COVID-19 vaccine accompanied by an mRNA vaccine injection had a possibility of a reduced infection risk than those who obtained both COVID vaccines of the AstraZeneca preventive. When the usage of AstraZeneca's vector-based COVID vaccine for persons under the age of 65 was discontinued because of safety issues, all Swedish individuals who had previously got their initial dose of this vaccination were advised to have an mRNA vaccine as a second dose. 

Citing Peter Nordstrom, the professor of Sweden's Umea University, PTI reported, “Having received any of the approved vaccines is better compared to no vaccine, and two doses are better than one. However, our study shows a greater risk reduction for people who received an mRNA vaccine after having received a first dose of a vector-based, as compared to people having received the vector-based vaccine for both doses.”   

The finding of the study was released in the Lancet Regional Health of Europe journal on Monday, October 17. The research was focused on countrywide registry data from the Swedish Public Health Agency, the National Board of Health and Welfare, and Statistics Sweden.  

Findings of the research on Mix-and-match COVID vaccines

Approximately 700,000 people participated in the primary analysis. Within the time period of 2.5-month average follow-up after the second dosage, the Lancet study found that the combination of AstraZeneca and Pfizer vaccination injections resulted in a 67% reduced chance of infection. Further, in comparison to unvaccinated people, people vaccinated with AstraZeneca and Moderna COVID vaccines had a 79% reduced chance of illness, according to the study. The risk decrease was 50% less for those who took two doses of the AstraZeneca vaccine, branded in India as Covishield. 

After taking into various considerations such as vaccination dates, participant ages, socio-economic level, and other COVID-19 risk variables, these risk estimations were discovered. According to the researchers, the study's efficacy was estimated during the time when the Delta variant was dominating the nation which many cases confirmed.

Marcel Ballin, a Ph.D. student at Umea University and co-author of the study stated that the research's findings might have consequences for vaccination methods in different nations. He went on to say that although there are encouraging results from earlier researches on an immune reaction from mix-and-match vaccination, yet, the World Health Organization has indicated that larger studies are needed to examine their efficacy and safety against clinical results. “Here we now have one such study," he added.  

Further, the researchers claimed that all vaccination regimens had a very low rate of unfavourable thromboembolic events or the development of blood clots in blood vessels. Even though Mix-and-match vaccination regimens have been shown in the past to produce a strong immunological response. However, the researchers noted that it was still unknown to what degree these regimens may lower the risk of clinical infection and that this study intended to fill that information gap. 

Image: AP