Adults are more likely to report mild and moderate side effects after a combination of AstraZeneca and Pfizer vaccines, a study suggests.
Shivering, headaches and muscle pain are often reported when different vaccines are combined.
Any adverse reaction is short-lived and there are no other safety issues.
Matthew “This is a very interesting find and not something to look forward to,” Professor Snape said.
The Com-Cov study, launched in February, looks at whether different vaccines at a second dose will give more reliable immunity, better prevent new strains, or simply allow clinics to exchange vaccines when supplies are discontinued.
Both Ontario and Quebec have said they plan to mix the vaccine in the near future due to uncertainty about the future of the Oxford vaccine and fears of rare blood clots.
The study, led by the University of Oxford, attracted 830 volunteers over 50 years.
The first full results are expected in June.
But the preliminary data is published in a study in the Lancet medical journal.
One in 10 volunteers who took two AstraZeneca vaccines four weeks apart reported fever, but if they were misled in any way and received a Pfizer, it increased to about 34 per cent
“The same practical differences apply to other symptoms such as chills, fatigue, headaches, discomfort and muscle pain,” says Professor Snape, the trial’s lead researcher.
“One of the things he tells us is that you don’t want to vaccinate a ward full of nurses on the same day (with mixed doses of different vaccines), because the next day you may have more absences.
In April, the study was expanded to include 1,050 volunteers to test the combination of modern vaccines and Nova Covid-19 with Astraznka and Pfizer.