On Apr. 14, 2021, researchers running the Com-Cov study, launched in February to investigate alternating doses of the Oxford-AstraZeneca vaccine and the Pfizer vaccine, have announced that the programme was extended to include the Moderna and Novavax vaccines in a new study. Led by the University of Oxford, the additional study sought to recruit adults aged over 50 who had received their first, or ﾑprimeﾒ vaccination in the past 8-12 weeks.