BRUSSELS: Fewer Europeans trust the AstraZeneca COVID-19 vaccine after several countries reported side-effects, such as blood clots, an opinion poll by YouGov showed on Monday, even though scientific studies have found it is safe and effective.

An increased number of French, German, Italian and Spanish adults said they considered the vaccine unsafe, YouGov found, although faith in other vaccines by Pfizer Inc and Moderna Inc was unaffected.

"Not only have we seen considerable rises in those who consider it unsafe in the last two weeks in Europe, the AstraZeneca vaccine continues to be seen as substantially less safe than its Pfizer and Moderna counterparts," lead data journalist at YouGov, Matt Smith said in a statement.

Sixty-one percent of French adults surveyed said the vaccine was unsafe, a rise of 18 percentage points compared to February, YouGov said.

Just over half of German adults surveyed said they thought the vaccine was unsafe, a rise of 15 percentage points compared to February, while 43% of Italians had serious doubts, an increase of almost a third.

Spain showed a similar increase to Italy in the level of concern, YouGov said. Only in Britain was trust in the vaccine stable.

While the European Medicines Agency (EMA) has investigated reports of unusual blood disorders in recipients of the AstraZeneca vaccine, it said last week the benefits outweighed the risks and continues to recommend its use.

This month a series of European countries, including France, Germany and Italy halted its use after Denmark and Norway reporting isolated cases of bleeding, blood clots and a low platelet count.

That was the latest setback in the European Union's troubled rollout of vaccines that has been dogged by delays.

As EU nations face a third wave of infections and their vaccination campaigns move more slowly than those of Britain and the United States, health experts have chided EU leaders for poor communication and said the vaccine AstraZeneca developed in partnership with Britain's Oxford University is safe.

YouGov pollster surveyed 1,672 British adults, 2,024 Germans, 1,022 French, 1,016 Italians, 1050 Spaniards, 1,004 Danes, and 1,017 Swedes between March 12 and March 18 2021.