SEOUL, South Korea — Health officials in South Korea are considering measures to prevent a shortage in coronavirus vaccines and haven't specifically ruled out curbing exports of AstraZeneca shots produced in the country.

Concern has been growing about delayed shipments of vaccines as the United States, European countries and India take steps to strengthen control over vaccine exports to deal with shortages at home.

When asked about the possibility of South Korea restricting vaccine exports, Korea Disease Control and Prevention Agency official Jeong Yoo-jin said Tuesday she wasn’t yet able to comment on specific steps but added that officials were reviewing “as much possible measures” they could.

Jeong’s tone seemed different from a briefing last week when she said clearly that officials weren’t considering restricting exports of the AstraZeneca shots manufactured by South Korea’s SK Bioscience. She then said such a move could trigger an international backlash that would potentially disrupt the country’s efforts to secure vaccines from different sources.

South Korea has wrestled with a slower rollout of vaccines than many other developed economies after officials insisted on a wait-and-see approach because its outbreak wasn’t as dire as in America and Europe. The country’s mass immunization program has so far been mainly reliant on locally produced AstraZeneca shots, although it did secure a smaller volume of Pfizer shots that are now being used for elders.

About a million South Koreans have received their first doses of vaccines as of Tuesday. Officials hope to vaccinate 70% of the country’s 51 million people before the start of the new influenza season around November.