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Mixing COVID-19 Vaccines Increased Side Effects

May 14, 2021 • 8:56 am CDT
(Precision Vaccinations News)

Mixing COVID-19 vaccines may produce more frequent mild to moderate reactions than standard vaccine dosing schedules, University of Oxford researchers reported in a peer-reviewed research letter published in The Lancet on May 12, 2021.

This study compared all four prime and boost permutations of the AstraZeneca and the Pfizer-BioNTech vaccines (Pfizer followed by AstraZeneca, AstraZeneca followed by Pfizer, AstraZeneca twice unmixed, and Pfizer twice unmixed) both at 28 days and 84-day, prime-boost intervals in 830 individuals.

'Both heterologous vaccine schedules induced greater systemic reactogenicity following the boost dose than their homologous counterparts, with feverishness reported by 37 (34%) of 110 recipients of ChAd for prime and BNT for boost compared with 11 (10%) of 112 recipients of ChAd for both prime and boost (difference 24%, 95% CI 13-35%).'

'Feverishness was reported by 47 (41%) of 114 recipients of BNT for prime and ChAd for boost, compared with 24 (21%) of 112 recipients of BNT for both prime and boost (difference 21%, 95% CI 8-33%).'

'Similar increases were observed for chills, fatigue, headache, joint pain, malaise, and muscle ache. There were no hospitalizations due to solicited symptoms, and most of this increase in reactogenicity was observed in the 48 hours after immunization.'

Matthew Snape, associate professor in pediatrics and vaccinology at the University of Oxford, said in a related BMJ article published on May 13th, “... it is important that we inform people about these data, especially as these mixed doses schedules are being considered in several countries."

“The results from this study suggest that mixed dose schedules could result in an increase in work absences the day after immunization, and this is important to consider when planning immunization of healthcare workers.”

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