The government is providing flu shots to the young and to senior citizens free of charge to reduce the burden on hospitals this winter amid the COVID-19 pandemic.
So far, the shots have been given to 8.3-6 million people.
But concerns are growing because nine people who got the vaccine died shortly after.
There is no evidence yet that the deaths were caused by the vaccine, and some of the people had underlying health conditions.
Several of the deaths occured on Wednesday, including a Daegu man in his 70s who reportedly had Parkinson's disease, and a man in Jeju known to have had high blood pressure.
A man in his 80s in Daejeon and a woman in her 70s in Gochang, Jeollabuk-do Province died on Tuesday one day after getting the vaccine and a high school student who got the vaccine died last week in Incheon.
The flu shots come from several different manufacturers, but for the shot given to the man in Jeju, the manufacturer has not yet been disclosed.
The deaths are being investigated, but there's no evidence yet of a link to the vaccine.
"No direct causality has been established between the flu shots and the deaths or abnormal responses."
Health authorities did say that two of the nine deaths could be related to anaphylactic shock, a serious allergic reaction that can occur after getting a vaccine.
But these findings, it seems, are not going to stop the flu vaccine's distribution.
"We have concluded that the state-run vaccination program should continue."
In the meantime, the government says it's going to look carefully at autopsy results and keep the public informed.
Han Seong-woo, Arirang News.