As of Thursday, some 30 people have died in South Korea after being vaccinated against influenza.
Public concerns have been amplified as deaths are occurring across the nation,with the first case coming from Incheon city followed by cases as far away as Daegu, and Jeju-island.
Most deaths are among elderly people in their 70s and 80s, who are considered a high-risk group.
The safety of the vaccine is also in question as a number of people reported symptoms after getting the shot with some suffering from fever and difficulty breathing as well as feeling nauseous.
This comes after half a million flu shots were recalled last month for being stored improperly.
However, the head of the Korea Disease Control and Prevention Agency, at a Thursday hearing in the National Assembly, said that this year's influenza vaccine is not toxic and therefore not responsible for the recent deaths.
"It has not yet been explained clearly that the recent deaths are related to the vaccine. And it's the investigation team's opinion that the likelihood is very low."
She said it would take up to two weeks to find out the exact cause of the deaths through autopsy, and emphasized the vaccination should not stop, especially for the elderly.
"Up to 3-thousand people die in one year due to the influenza itself. As the influenza can worsen underlying diseases leading to the cause of death, it's safer to get the shot."
The government will continue to distribute the flu vaccine and conduct further epidemiological investigations,unless there are more deaths among people getting the same vaccines as used in previous cases.
The National Forensic Service meanwhile confirmed Thursday through an autopsy that the first case, the death of a 17-year-old has no connection to the vaccination itself.
Choi Jeong-yoon, Arirang News.