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Preliminary data suggests mixing Covid-19 vaccine increases reactogenicity

Researchers running the University of Oxford-led Com-COV study – launched earlier this year to investigate alternating doses of the Oxford-AstraZeneca vaccine and the Pfizer vaccine – report preliminary data revealing more frequent mild to moderate reactions in mixed schedules compared to standard schedules.

  • Research, from Com-COV study comparing mixed dosing schedules of Pfizer / Oxford-AstraZeneca vaccines, shows increase in the frequency of mild-moderate symptoms in those receiving either mixed dosing schedule
  • Adverse reactions were short-lived, with no other safety concerns
  • Impact of mixed schedules on immunogenicity unknown as yet, with data to follow from this study

Writing in a peer-reviewed Research Letter published in the Lancet, they report that, when given at a four-week interval, both of the ‘mixed’ schedules (Pfizer-BioNTech followed by Oxford-AstraZeneca, and Oxford-AstraZeneca followed by Pfizer-BioNTech) induced more frequent reactions following the 2nd, ‘boost’ dose than the standard, ‘non-mixed’ schedules. The add that any adverse reactions were short lived and there were no other safety concerns.

Read the full story on the University of Oxford website