Short-lived common side effects including fever, chills, pain, and headache after mixing AZ with Pfizer vaccine reported in @TheLancet. Immunogenicity results to be reported in June and if mixing is a viable option (likely but assumption needs evidence).

Medical Mythbusting Commentary for May 13, 2021

Source:
Mixing Covid-19 vaccines tied to more side effects, early UK data suggests

Reference:
Heterologous prime-boost COVID-19 vaccination: initial reactogenicity data

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