The mixed doses of two different COVID-19 vaccines lead to increased side effects, such as fatigue and headaches, the initial results of a study, published in The Lancet journal showed. For this study, researchers gave participants one dose of AstraZeneca’s coronavirus vaccine and the second dose of Pfizer/BioNTech’s vaccine. They also switched the order of vaccine doses.

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They found out that people who got such a mix, with the second dose four weeks after the first, reported more short-lived side effects, most of them mild.

10% of the participants, who got the mixed dosage, reported severe fatigue, compared to 3% for those given the same vaccine.

All the participants in the study were above 50 years of age. It’s possible that the reactions could be even stronger in younger patients, said Matthew Snape, an Oxford pediatrics and vaccinology professor who’s leading the study.

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The professor termed the findings as “intriguing” and not “something that we were necessarily expecting,” Bloomberg reported.

Although the study has hinted towards side effects, it’s still not clear if it leads to improved immune response.

“We don’t know yet; we’ll be finding out those results in a few weeks’ time,” he told the media house. 

If such a mix shows positive results, it’ll be good news for several low and middle-income countries that are facing vaccine shortages. 

Also read: COVID patients should defer vaccination for 6 months after recovery: Centre

Currently, mixed vaccine doses are being administered in France, where a person who was given the first dose of AstraZeneca’s vaccine can get Pfizer’s vaccine for the second dose. The European country has suspended the the use of AstraZeneca vaccine.