'Really intriguing' results when vaccines are mixed

Top News | AGENCIES 14 May 2021

Muscle pain, headaches and other mild to moderate side-effects are more likely to affect adults after mixing AstraZeneca and Pfizer-BioNTech Covid vaccines, a study has found.

And the Oxford Vaccine Group said any adverse reactions are short-lived, with no other safety concerns.

"It's a really intriguing finding and not something we were necessarily expecting," said professor Matthew Snape, the trial's chief investigator.

The group is expected to publish its first full results next month but preliminary data has been published in the medical journal the Lancet.

The study was launched in February to see whether a different jab for the second dose might give longer-lasting immunity, better protection against new variants or simply allow clinics to swap jabs if supplies are interrupted.

The Canadian provinces of Ontario and Quebec have both said they plan to mix vaccines in the near future, amid uncertainty over shipments of the Oxford-AstraZeneca vaccine and concerns about rare blood clots, the BBC reported. The study recruited 830 volunteers aged over 50.

One in 10 volunteers given two AstraZeneca jabs four weeks apart reported feverishness - but if they received one AstraZeneca jab and one Pfizer, in any order, the proportion rose to about 34 percent.

"The same real differences applied for other symptoms such as chills, fatigue, headache, malaise and muscle ache," said Snape.

The study was expanded last month, adding another 1,050 volunteers to test combinations using Moderna, Novavax, AstraZeneca and Pfizer.

US states, meanwhile, began using Pfizer vaccines to inoculate younger adolescents after advisers to the US Centers for Disease Control and Prevention backed the plan in a unanimous vote.

The US Food and Drug Administration had authorized the vaccine for children aged 12 to 15, offering relief to parents eager to get their children back to schools and summer camps. The action by the CDC group is an important, but not required, final seal of federal regulatory approval.

The Advisory Committee on Immunization Practices, which provides recommendations to the CDC, voted 14-0 to back the vaccine after reviewing trial evidence. That showed no one in the 12-15 age group who received the vaccine got Covid, and there were no cases of Bell's Palsy or severe allergic reactions.

Moreover, the vaccine produced robust antibody responses in the age group and showed 100 percent efficacy in the trial, with no cases of symptomatic Covid among the fully vaccinated adolescents.

About a third of all Americans have been fully vaccinated. The rollout of a vaccine for adolescents should help limit the spread of the virus at a time when more contagious variants are circulating.

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