JAKARTA, Jan. 14 (Xinhua) -- Indonesia launched its massive COVID-19 vaccination program on Thursday with health workers as the main priority group, a day after President Joko Widodo received the first shot developed by China's biopharmaceutical company Sinovac Biotech.

On Thursday morning, a mass vaccination was held at state-run Cipto Mangunkusumo Hospital in central Jakarta.

At least 25 health workers at the hospital have received doses of the Sinovac vaccines, the hospital's director Lies Dina Liastuti told a press conference, adding that about 6,000 health workers nursing COVID-19 and non-COVID-19 patients at the hospital are to be vaccinated periodically.

"Thanks to the government for providing protection to health workers by providing the COVID-19 vaccines," Liastuti said.

Deputy Minister of Health Dante Saksono, who received a dose of the vaccine at the hospital on Thursday, said about 1.4 million health workers across the country will be injected gradually before the public servants get inoculated.

According to Saksono, immunity would appear between two and six weeks after the injection of the second dose of the vaccine. But those who have been vaccinated still need to implement health protocols, he said.

The deputy minister expressed hope that the massive vaccination program would help Indonesia get herd immunity after 70 percent of the 270-million population is inoculated.

The country's food and drug authority BPOM issued an emergency use authorization for Sinovac's COVID-19 vaccine on Monday after interim results of its late-stage trials in the country.

The vaccine has also been declared by the Indonesian Ulema Council (MUI) halal, or acceptable for use under Islamic law.

Indonesia has ordered a total of 125.5 million doses of the Sinovac vaccine. Currently 3 million ready-to-use doses, which were delivered to the country in two batches in December last year, have been distributed to the 34 Indonesian provinces.

On Tuesday, another 15 million doses of raw materials of the Sinovac vaccine arrived at Indonesia's Soekarno-Hatta Airport. They will be brought to the office of the state vaccine manufacturing company Bio Farma in West Java for further process into ready-to-use doses.

President Widodo said last week that his country has ordered a total of 329.5 million doses of vaccines from various pharmaceutical manufacturers. Apart from those from Sinovac, it has also secured vaccine supplies from British-Swedish biopharmaceutical company AstraZeneca and U.S. company Novavax, among others.

Indonesia plans to vaccinate about 180 million people, or two thirds of the population in a period of 15 months. The COVID-19 vaccines will be offered free of charge for all Indonesians.