Britain’s Prime Minister Boris Johnson with quality control technician Kerri Symington, visits the French biotechnology laboratory Valneva in Livingston, Scotland on Jan. 28. (AP photo)

LONDON — Scotland’s COVID-19 vaccination program has led to a sharp drop in hospitalizations, researchers said Monday, boosting hopes that the shots will work as well in the real world as they have in carefully controlled studies.

The Oxford-AstraZeneca vaccine reduced hospital admissions by up to 94% four weeks after people received their first dose, while the Pfizer-BioNTech vaccine cut admissions by up to 85%, according to scientists at the University of Edinburgh, the University of Strathclyde and Public Health Scotland.

The preliminary findings were based on a comparison of people who had received one dose of vaccine and those who hadn’t been inoculated yet. The data was gathered between Dec. 8 and Feb. 15, a period when 21% of Scotland’s population received their first vaccine shot.

“These results are very encouraging and have given us great reasons to be optimistic for the future,” said Professor Aziz Sheikh, director of the University of Edinburgh’s Usher Institute. “We now have national evidence — across an entire country — that vaccination provides protection against COVID-19 hospitalizations.”

About 650,000 people in Scotland received the Pfizer vaccine during the study period and 490,000 had the AstraZeneca shot, according to the Usher Institute. Because hospitalization data was collected 28 days after inoculation, the findings on hospital admissions were based on a subset of 220,000 people who received the Pfizer vaccine and 45,000 who got the AstraZeneca shot.

U.K. regulators authorized widespread use of the AstraZeneca vaccine on Dec. 30, almost a month after they approved the Pfizer vaccine.

Outside experts said while the findings are encouraging, they should be interpreted with caution because of the nature of this kind of observational study. In particular, relatively few people were hospitalized after receiving the vaccines during the study period.

Stephen Evans, a professor of pharmacoepidemiology at the London School of Hygiene & Tropical Medicine, urged those making political decisions about the pandemic to be cautious.

“It will be important that euphoria, especially from political sources that do not understand the uncertainty in the numerical values, does not cause premature decisions to be made,” he said “Cautious optimism is justified.”

Earlier this month, Israel reported encouraging results from people receiving the Pfizer vaccine. Six weeks after vaccinations began for people over age 60, there was a 41% drop in confirmed COVID-19 infections and a 31% decline in hospitalizations, according the country’s Ministry of Health.