Prime Minister Chung Sye-kyun on Friday called for a thorough probe into the deaths of people after being vaccinated against seasonal influenza.
As of midnight Thursday, 30 people have died after inoculation, but health authorities found no direct links between the vaccine and fatalities.
"I offer my deep condolences to the bereaved families," Chung said at a meeting of the Central Disaster and Safety Countermeasure Headquarters.
"The authorities should thoroughly investigate the causal relationship between vaccinations and the deaths, and make public the development transparently."
He noted the public remains nervous despite experts' denial of the connection between the deaths and flu shots.
"I call on the Korea Disease Control and Prevention Agency (KDCA) to closely consult experts and do its best to take sufficient measures and explain swiftly so that people can receive vaccinations without anxiety," he added.
On Thursday, the government affirmed the immunization program will continue despite suspected deaths.
The country has been pushing for the free flu shot scheme for some 19 million people, including teenagers and senior citizens, to curb the possible "twindemic."
Fears over flu vaccines first emerged last Friday after a 17-year-old boy in the western port city of Incheon died two days after receiving a flu shot.
Similar fatalities have been reported, mostly among senior citizens with underlying diseases. (Yonhap)