Cyprus said Wednesday it would not make available 2,400 Johnson & Johnson vaccines it received pending an investigation into several cases of thrombosis in the US.

The health ministry said the recommendation to pause vaccinations was given by the manufacturer pending the investigation. The US drugs administration and Europe’s EMA are also expected to issue guidelines following the examination of the cases.

The European Medicines Agency (EMA) is examining the possible link between the vaccine and thrombosis, stressing that “it is not clear at this time that there is a link between the vaccine and the clots”. According to the EMA, it continues to investigate the issue and to consider what actions to take and what recommendation to make.

The EMA, Europe’s drug regulator said last Friday it was reviewing rare blood clots in four people in the United States who received Johnson & Johnson’s Covid-19 vaccine, a single-dose jab.

The EMA’s safety committee has also been looking at how AstraZeneca’s vaccine is associated with very rare cases of unusual blood clots and said it was now reviewing reports of capillary leak syndrome in people given AstraZeneca’s vaccine.

Johnson & Johnson (J&J) said it was aware of the rare reports of blood clots in individuals given its vaccine, and was working with regulators to assess the data and provide relevant information.

US federal health agencies on Tuesday recommended pausing use of Johnson & Johnson’s vaccine for at least a few days after six women under age 50 developed rare blood clots after receiving the shot, dealing a fresh setback to efforts to tackle the pandemic.