- UPDATED: May 13, 2021 21:51 IST
As the coronavirus cases surge and people rush to vaccination centres to get their dosage, a new report has called for ensuring caution stating that people who got mixed doses of the Covid-19 vaccine appear to be more likely to experience mild or moderate side effects. These effects could range from fever, chills to headache.
As countries face a shortage of coronavirus vaccine due to sudden pressure on companies to ramp up production, people are mixing vaccines based on their availability–getting a different vaccine as a second dose than the first one.
In a report published in Lancet medical journal, researchers pointed that the side effects are more or less of the same type that occurs during the first dose, but it’s the frequency of the occurrence of the symptoms that is changing when two vaccines are mixed.
“These are the type of reactions you do expect with the vaccine,” CNN quoted Dr Matthew Snape, an associate professor of paediatrics and vaccinology at the University of Oxford and chief investigator on the trial, as saying during a media briefing. He further added “They are more or less the same types of reactions that you’re seeing with the standard schedules. It’s just that they’re occurring more frequently, and we’re seeing both more frequent both in mild and moderate symptoms — but they resolved quickly.”
The research was conducted by Oxford Vaccine Group’s Com-Cov vaccine trial, which is studying the use of different combinations of approved Covid-19 vaccines for the first and second immunisation dose. A total of 830 volunteers who were randomly assigned to four different vaccine schedules involving the Oxford/AstraZeneca and Pfizer/BioNTech vaccines, with first and second doses given 28 days apart were observed.
Mixed vaccines resulting in faster side effects
During the study, the volunteers were administered a combination of vaccines either AstraZeneca as a first dose and Pfizer as a second dose; Pfizer as both doses or AstraZeneca as both doses. The Lancet report states that it was observed that people who got mixed dosage had more side effects with 34 per cent reporting feeling feverish, compared to only 10 per cent who were given Astera Zeneca as both dosages.
Meanwhile, 41 per cent of volunteers who received the Pfizer vaccine first and the AstraZeneca vaccine second reported experiencing fever as a side effect compared to only 21 per cent of volunteers given the Pfizer vaccine for both doses experiencing such side effects.
While most of the side effects were seen 48 hours after the immunisation, there was no case of hospitalisation. Researchers are now calling for further study to evaluate the immune response of mixed dosage. “We do think reactions often relate to the stimulating of the innate immune response,” Snape said. “Whether or not this will relate to actually an improved immune response we don’t know yet. We’ll be finding out those results in a few weeks time,” CNN quoted him as saying.
No such guidelines on mixing vaccines
The World Health Organisation, the US Centre for Disease Control or ICMR in India have not recommended mixing vaccines in a bid for faster immunisation based on availability.