LONDON — U.K. regulators went on the offensive Friday to beat back criticism that they rushed their authorization of a COVID-19 vaccine, saying they rigorously analyzed data on safety and effectiveness in the shortest time possible without compromising the thoroughness of their review.

The comments from the Medicines and Healthcare Products Regulatory Agency came as the Times newspaper reported that the agency’s chief executive, Dr. June Raine, planned to give a series of radio interviews so she could speak directly to people who may be concerned about getting vaccinated.

The MHRA reiterated earlier statements that the agency is conducting rolling reviews of COVID-19 vaccine candidates, allowing regulators to speed up the review process by looking at data as it becomes available. The agency gave emergency approval on Wednesday to a vaccine produced by U.S. drugmaker Pfizer and Germany-based BioNTech, making Britain the first Western country to authorize a vaccine against the coronavirus.

The ability to act more quickly “does not mean steps and the expected standards of safety, quality and effectiveness have been bypassed,” the MHRA said. “No vaccine would be authorized for supply in the U.K. unless the expected standards of safety, quality and efficacy are met.”

The media blitz comes amid concerns that criticism of the approval process could undermine public confidence in the Pfizer/BioNTech vaccine, leading some individuals to shun shots. Britain plans to begin vaccinating people within the next few days, starting with nursing home residents, caregivers and people over age 80.

Britain will initially receive 800,000 doses, enough to vaccinate 400,000 people, so the first shots will go to those who are most at risk of dying from COVID-19 and those who are most likely to spread the coronavirus.