New study documents possible adverse events in relation to Vaxzevria COVID-19 vaccine The new Danish-Norwegian study is the first study to document possible adverse events in relation to the COVID-19 vaccine Vaxzevria from AstraZeneca, in which all vaccine recipients have been followed systematically, as opposed to previous studies, which have relied primarily on reported adverse reactions. The new study was a cooperation between Danish and Norwegian research institutions. - In this study, we were able to identify all hospital contacts among vaccinated persons by utilising the unique Danish and Norwegian health registers. This ensures that we get a comprehensive of the rate of adverse reactions. Previous studies have been dependent on spontaneous reporting of adverse events in individual patients, which carries a risk of under-reporting, says Anton Pottegård, who is a professor at the University of Southern Denmark and co-author of the study.