South Korea suspended its plan to offer free seasonal flu vaccines due to storage issues involving inactivated bottles, health authorities here said Tuesday.

The government was to provide free flu shots to around 19 million people, or 37 percent of the country's population.

Children between six months and 18 years old, pregnant women and those aged 62 years old or above were included.

The Korea Disease Control and Prevention Agency (KDCA) said some of around 5 million doses of flu vaccines were partially exposed to temperatures outside the storage range.

Inactivated vaccines should be stored in refrigerators, and exposure to room temperature could result in decreased vaccine potency and increased risk of vaccine-preventable diseases.

The KDCA later said that if the exposed vaccines pass quality tests, they will be administered to those in the 13-18 age bracket, followed by the older demographic. Those tests, to be run by the Ministry of Food and Drug Safety, will take about two weeks, according to the KDCA.

The KDCA wouldn't commit to destroying all 5 million vaccine doses, saying it will wait for the results of quality tests before deciding.

As autumn is approaching, the government was to provide free flu shots, as it is not easy to distinguish the novel coronavirus and flu patients due to similar symptoms, such as coughing, a sore throat and fever. (Yonhap)