President Tsai Ing-wen received a shot of the domestically made vaccine at a hospital in the capital, Taipei, giving her personal assurance of its safety.

“It didn’t hurt,” Ms. Tsai wrote in a Facebook post. “Now, I am in good spirits, and I will continue my daily work.”

The vaccine, which was developed by the Taiwan-based company Medigen, received authorization for emergency use in late July. But critics say they worry that the vaccine, which has completed Phase 2 trials, is being used before its effectiveness and safety have been proved.

Two politicians from the island’s main opposition party, Kuomintang, recently filed a complaint to a local court seeking to suspend the emergency authorization, citing the concerns over the vaccine’s safety. The court dismissed their request last week.

Taiwan, where fewer than 10 locally transmitted cases are reported each day, has favored a less heavy-handed approach to the virus than neighboring mainland China. Since an outbreak that began in May, the government has introduced a series of measures to promote vaccination and received donations of doses from countries including the United States and Japan.

In the past few months, the island’s vaccination rate has increased significantly. As of Monday, around 40 percent of residents had received at least one dose. But only about 3 percent are fully vaccinated. Taiwan has recorded 15,926 total cases of the virus and 828 deaths, according to a New York Times database.

Nearly 600,000 of Taiwan’s 23.5 million residents have registered to get Medigen shots, according to the government data.