U.K. officials issued a warning to citizens after its regulators approved Pfizer's vaccine for emergency use.
The U.K.'s deputy chief medical officer said, "Low uptake will almost most certainly make restrictions last longer."
Both Prime Minister Boris Johnson and health officials say citizens still need to make sacrifices until the vaccine is widely deployed.
Johnson has ended national restrictions but said they will be replaced with "tough tiers" to curb the spread.
