Germany, France and Italy said on Monday they would suspend AstraZeneca COVID-19 vaccination after several countries reported possible serious side-effects such a blood-clotting and death.
However, World Health Organization (WHO) and AstraZeneca claims there are no direct links to any side-effects from the vaccine.
The decision to suspend vaccination has affected European Union (EU) hopes of ending the pandemic by summer.
Denmark and Norway stopped giving the shot last week after reporting isolated cases of bleeding, blood clots and a low platelet count. Iceland and Bulgaria followed suit and Ireland and the Netherlands announced suspensions on Sunday.
Spain is set to suspend AstraZeneca vaccine for up to 15 days.
The WHO said its advisory panel was reviewing reports related to the shot and would release its findings as soon as possible. But it said it was unlikely to change its recommendations, issued last month, for widespread use, including in countries where the South African variant of the virus may reduce its efficacy.
Germany said it was facing a third wave of infections, Italy is intensifying lockdowns and hospitals in the Paris region are close to being overloaded.