Covid-19: Fever, chills, and aches more common when AstraZeneca and Pfizer vaccines are mixed, early data show

Mixing doses of the Oxford AstraZeneca and the Pfizer BioNTech covid-19 vaccine leads to more frequent mild to moderate reactions compared with standard dosing schedules, researchers have reported. Researchers running the University of Oxford led Com-COV study—which is investigating the reactogenicity and immunogenicity from mixing doses of the two vaccines—reported their preliminary results in a peer reviewed research letter in the Lancet. Matthew Snape, associate professor in paediatrics and vaccinology at the University of Oxford and chief investigator on the trial, said, “While this is a secondary part of what we are trying to explore through these studies, 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 immunisation, and this is important to consider when planning immunisation of healthcare workers.”