Mixing and matching COVID-19 vaccines may reduce risk of infection, study finds

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Experts say mixing the Pfizer or Moderna vaccines with the AstraZeneca vaccine led to positive results

A new study conducted by researchers from Umea University explored how the different types of COVID-19 vaccines may impact consumers’ health outcomes. Their findings showed that consumers who received one dose each of the AstraZeneca and mRNA vaccines had a lower risk of COVID-19 infection

“Having received any of the approved vaccines is better compared to no vaccine, and two doses are better than one,” said researcher Peter Nordström. “However, our study shows a greater risk reduction for people who received an mRNA vaccine after having received the first dose of a vector-based, as compared to people having received the vector-based vaccine for both doses.” 

How do the different vaccines impact consumers’ health?

For the study, the researchers analyzed data from nearly 700,000 people enrolled in the Public Health Agency of Sweden, the National Board of Health and Welfare, and Statistics Sweden. 

The team explained that it was recommended that AstraZeneca’s vaccine wasn’t used on consumers under the age of 65; for those who had received the first dose of that shot, experts recommended they get one of the mRNA vaccines for their second dose. The researchers followed the participants over the course of nearly three months to see how well the two vaccines worked to protect consumers from COVID-19. 

Ultimately, the researchers learned that participants who received one dose of the AstraZeneca vaccine and a second dose of either the Moderna or Pfizer mRNA vaccines had a lower risk of infection than those who were either unvaccinated or received two doses of the AstraZeneca shot. 

Getting one round of AstraZeneca and one round of the Moderna vaccine was linked with a nearly 80% lower risk of developing COVID-19, while one round of the Pfizer vaccine was linked with a nearly 70% lower risk of infection. On the other hand, receiving two doses of the AstraZeneca vaccine was associated with a 50% lower risk of contracting COVID-19. 

The researchers explained that these findings held up even after accounting for several of the known risk factors of COVID-19, including participants’ age. 

“The results of the study may have implications for vaccination strategies in different countries,” said researcher Marcel Ballin. “The World Health Organization has stated that despite the promising results from previous studies regarding immune response from mix-and-match vaccination, there is a need for larger studies to investigate their safety and effectiveness against clinical outcomes. Here we now have one such study.” 

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