GSK Korea said Thursday that an entire family can now use its Fluarix Tetra quadrivalent flu influenza vaccine, as the government had approved its use for infants between 6 months and 3 years old.

Flu influenza is an acute virus infection that spreads quickly and can lead to moderate to severe disease and even death. The condition includes symptoms such as chills, cough, headache, muscle pain, joint pain, anxiety, sore throat, and runny nose.

The Ministry of Food and Drug Safety’s expanded approval on April 27 allows for the vaccine’s used for infants, children, adolescents and adults.

The vaccine had recorded largest sales among quadrivalent products for two consecutive years since 2016 in Korea, the IQVIA data shows.

“According to the World Health Organization, there are 3 to 5 million severe cases of influenza worldwide and estimated deaths of 280,000 to 650,000 a year,” said Lee Jae-hyuk, GSK Korea’s medical advisor, at a news conference at the Plaza Hotel in downtown Seoul.

Although the mortality rate for flu is low in infants, the hospitalization rate and social costs are high. Parents must take a day off work while infants act as carriers that can transmit the disease to guardians including grandparents, Lee said.

Dr. Philippe Buchy, director of scientific affairs and public health in GSK Vaccines, explained about the advantage of vaccinating infants in his presentation of clinical trial data for Fluarix Tetra.

“By vaccinating children, you have two advantages; you prevent the disease in children, and you prevent the children from affecting the adults, including the grandmother and grandfather, without having to vaccinate the older people,” Buchy said.

“Now many countries such as the U.K. are considering vaccinating all school-age children to decrease the overall burden of flu in the community,” he said.

According to clinical trials, Fluarix Tetra showed a 63.2 percent preventive efficacy in preventing moderate to severe flu in infants, and 49.8 percent efficacy overall.

“You may say that this is not that impressive, but we need to consider that during the study almost all the H3N2 strains recommended in the vaccine did not match the strains circulating. Initially, we expected a lower response. So this was impressive data,” Buchy said.

He went to say, “If you look at the data, when you have a perfect match between the vaccine and the strains circulating in the country, vaccine efficacy was 77 percent, meaning 77 percent of vaccinated people are protected. When you don’t have a good match, the vaccine protected 25 percent fewer people.”

The vaccine also improved other essential healthcare outcomes such as the use of antibiotics and number of hospital visits, Buchy noted.

Trial findings showed the use of antibiotics in infants dropped 50 percent, the number of hospital and clinic visits by 47 percent, parents calling out of work by 54 percent, and emergency room visits by 79 percent.

“These are factors we don’t look at often but are important,” Buchy said.