Kate Bingham, a UK government official, after being vaccinated in London in October 2020. She did not take the Oxford/AstraZeneca vaccine. Kirsty O'Connor/PA Images via Getty Images Oxford University and AstraZeneca announced on Monday that their vaccine works — but the story soon got messy. AstraZeneca's Mene Pangalos said a group of study participants received a lower dose by accident, prompting a wave of criticism from experts. There are legitimate reasons to criticise the vaccine, questioning details of the development process and its precise effectiveness. But it is important not to overhype the problems — the vaccine has been proved safe and could become a powerful weapon against COVID-19. Visit Business Insider's homepage for more stories. AstraZeneca and Oxford University's high-profile announcement on Monday of a working vaccine has soured in the days that followed.After promising headline results, it became clear that the development process had been less than perfect, with some participants mistakenly given a smaller dose, which appeared to actually make it more effective.On Thursday, after a wave of criticism, its CEO admitted there were problems in the process and pledged to run another study.