Analysis: From game-changer to back-up: J&J's COVID vaccine struggles in Europe

FILE PHOTO: Vials labelled "COVID-19 Coronavirus Vaccine" and sryinge are seen in front of displayed Johnson&Johnson logo in this illustration taken, February 9, 2021. REUTERS/Dado Ruvic/Illustration/File Photo

BRUSSELS (Reuters) - At the height of Europe's vaccine supply crisis in March, Johnson & Johnson's (J&J) single-dose COVID-19 vaccine was touted as a game-changer. But two months into its rollout, the shot has the lowest uptake of all four approved vaccines.

Supply problems, safety concerns, improved deliveries of rival vaccines and countries' inoculation strategies have all played a part in holding back usage.