AstraZeneca says it has suspended trials of the coronavirus vaccine it is developing with the University of Oxford after one of the trials' volunteers fell ill with an unexplained illness.
The UN says the disruption to routine child and maternal health services as a result of the pandemic could put millions of lives at risk and undo years of progress in reducing child mortality.
More than 27.5 million people around the world have been diagnosed with the coronavirus and 897,383 have died. More than 18.5 million people have recovered.
Safety of a prospective vaccine for COVID-19 comes "first and foremost", said the World Health Organization's chief scientist, as a trial of a candidate from AstraZeneca was temporarily paused due to concerns over side effects.
"Just because we talk about speed...it doesn't mean we start compromising or cutting corners on what would normally be assessed," Soumya Swaminathan said on 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.