(Photo: PAP/VNA)

The watchdog said a relationship between GBS and the AstraZeneca shot is at least a reasonable possibility after 833 cases of GBS were reported out of 592 million doses of the vaccine given worldwide by July 31. The EMA categorized the side-effect as "very rare", the lowest frequency of side-effect category it has, and emphasized that the benefits of the shot outweigh the risks.

The EMA also tagged some other less severe side-effects to vaccines from Johnson & Johnson and Moderna.