ZURICH/GENEVA (Reuters) - Safety of a prospective COVID-19 vaccine comes "first and foremost", the World Health Organization's chief scientist said on Wednesday, as a trial of a leading candidate from AstraZeneca was paused due to concerns over side effects.

Rollout of an effective vaccine is seen as a crucial step in helping battered economies recover from the coronavirus pandemic.

"Just because we talk about speed...it doesn't mean we start compromising or cutting corners on what would normally be assessed," Dr. Soumya Swaminathan said in a social media event.

"The process still has to follow through rules of the game. For drugs and vaccines which are given to people, you have to test their safety, first and foremost," she said.

WASHINGTON — In early August, more than 460,000 motorcycle enthusiasts converged on Sturgis, S.D., for a 10-day celebration where few wore facial coverings or practiced social distancing. A month later, researchers have found that thousands have been sickened across the nation, leading them to brand the Sturgis rally a “superspreader” event.