The EU's drug regulator said Friday it had launched a review of possible links between the Johnson & Johnson coronavirus vaccine and blood clots after reports of four cases, one of them fatal. The European Medicines Agency (EMA) said its safety committee "has started a review of a safety signal to assess reports of thromboembolic events" with people who had received the shot. "Four serious cases of unusual blood clots with low blood platelets have been reported post-vaccination with Covid-19 Vaccine Janssen," the EMA said, referring to US pharma giant J&J's European subsidiary. "One case occurred in a clinical trial and three cases occurred during the vaccine rollout in the USA. One of them was fatal." The watchdog has approved the Johnson & Johnson vaccine for use but its rollout across the 27-nation EU is not due to start until later this month. The probe comes days after the Amsterdam-based watchdog said it was listing the same type of blood clots as a very rare side effect of the rival AstraZeneca vaccine. Both jabs use similar adenovirus vector technology. dk/jhe/jv