The European Union's drug watchdog and lawmakers warned against hasty approvals of Covid-19 vaccines on Wednesday, after Britain granted emergency authorisation to the experimental Covid-19 shot being developed by Pfizer and BioNTech.

Britain is the first Western country to approve a Covid-19 vaccine, a move that many see as a political coup for Prime Minister Boris Johnson's government, which has faced criticism over its handling of the coronavirus crisis.

The decision was made under an emergency, ultra-fast approval process...