Influenza is spreading rapidly in South Korea at the start of autumn, prompting health authorities to consider moving up the national vaccination program originally scheduled to begin on the 21st. Cases are climbing sharply among children and adolescents, and hospitalizations have surpassed 10 times the level recorded in the same period last year, raising alarm over an unusually early outbreak.
Twice the Epidemic Threshold, 10 Times the Hospitalizations — Ages 7-12 Hit Hardest
In the 36th week of the year, or Aug. 30 to Sept. 5, the first week of the 2026-2027 season, 25.3 out of every 1,000 outpatients at sentinel surveillance clinics showed influenza-like symptoms, according to the Korea Disease Control and Prevention Agency on the 14th. That is roughly twice this season's epidemic threshold of 12.9.
The agency issued an influenza epidemic advisory as of midnight on the 11th. That is more than a month earlier than last season, when the advisory came on Oct. 17.
The spread is most pronounced among children and adolescents in group settings such as schools. Among those aged 7 to 12, the rate of influenza-like illness climbed to 75.1 per 1,000 outpatients.
Hospitalizations, an indicator of severe cases, also rose steeply. Over the same period, hospital-level medical institutions reported 300 influenza inpatients, more than 10 times the 23 recorded a year earlier.
Jung Jae-hun, a professor of preventive medicine at Korea University College of Medicine, said the pattern of respiratory virus outbreaks has been shifting since the COVID-19 pandemic. "The timing of outbreaks in 2024, 2025 and 2026 has been slightly off each year, and this year the outbreak began early as well, showing that the aftereffects of the pandemic are continuing," the professor told Newsis, adding that immunity and climate factors may have played a role.
Experts nonetheless said the early start does not necessarily mean the total number of cases will greatly exceed previous years. "The common view among experts is that the scale of the outbreak itself is unlikely to differ much from previous years," the professor said, while noting the outbreak period could last longer.
Vaccination Schedule Under Review After Planned Sept. 21 Start — "State Vaccine Supply Is Sufficient"
The faster-than-expected spread has led the agency to revisit its vaccination timetable. The national immunization program for the 2026-2027 season was initially set to begin on the 21st, rolling out by group. Free shots are offered to children aged 6 months to 14 years, pregnant women and people aged 65 and over. Starting this year, eligibility for children was expanded to age 14 from 13.
At a regular briefing on the 14th, an agency official said authorities are "closely reviewing options to adjust the schedule by group for children and older adults," adding that the timetable will be finalized after gathering input from local governments and the medical community over the next two to three days.
Separate measures have already been taken for nursing hospitals and long-term care facilities, where high-risk patients are concentrated. Those facilities may begin vaccinations as soon as they secure doses, without waiting for the designated schedule.
The agency dismissed concerns about a vaccine shortage. Although flu is also spreading overseas and global influenza vaccine output has declined, it said it has secured ample supplies for the national program.
"Vaccine production has fallen globally, but we have secured more than enough vaccine for the national immunization program, and there is no shortage," an agency official told Yonhap News.
Supplies of paid vaccines for people outside the state-funded program are expected to fall short of previous years, however. The agency said the overall production decline has reduced volumes distributed through the private market, and that it will continue to monitor for any delays in supply.
The agency also said it has secured the antiviral supplies currently needed. Authorities plan to adjust the vaccination schedule to match a flu outbreak that arrived more than a month earlier than expected, while closely monitoring the spread and severe cases among high-risk groups including children, adolescents and older adults.
