Influenza and COVID-19 Cases Surge Simultaneously, Making a 'Twindemic' a Reality as Schools Reopen... When Should You Get Vaccinated? [Health Talk]

[Financial News] The number of people suspected of having influenza has doubled in four weeks, while influenza hospitalizations have nearly quadrupled. With COVID-19 also rebounding, a warning light has come on for a 'twindemic.'
Influenza and COVID-19 cases are surging simultaneously as the new school term begins and the seasons change. According to infectious disease sentinel surveillance results released by the Korea Disease Control and Prevention Agency (KDCA) for epidemiological week 35 of 2026 (Aug. 23–29), the rate of influenza-like illness at clinics and other primary-care medical institutions reached 13.3 per 1,000 outpatients, nearly doubling from 7.0 in week 32 in just four weeks. The number of influenza hospitalizations at hospitals also surged nearly fourfold, from 43 in week 32 to 162 in week 35.
By age group, the rate of influenza-like illness was highest among children aged 7–12, at 36.5 per 1,000 people, followed by children aged 1–6, at 22.6. The outbreak is accelerating primarily among children and adolescents who spend time in group settings.
There are also concerns that COVID-19 may be making a comeback. COVID-19 hospitalizations rose 78.7% in one week, from 61 in week 34 to 109 in week 35. An analysis of respiratory infection specimens from patients suspected of having respiratory infectious diseases at clinics found detection rates of 12.3% for influenza viruses and 11.7% for COVID-19 viruses, indicating that both viruses continue to trend upward.

When influenza and COVID-19 are spreading simultaneously, the most effective preventive measure is to get vaccinated before the outbreak takes hold. Influenza viruses undergo genetic changes every year, causing the dominant circulating strains to vary. To reflect these changes, the World Health Organization (WHO) recommends new vaccine strains twice a year. This is why people need to receive the newly released vaccine for each season, even if they were vaccinated last year.
According to the '2024–2025 Seasonal Influenza Annual Report' released by the KDCA, an assessment of vaccine effectiveness estimated that protection against infection ranged from 10.2% to 41.4%, protection against hospitalization from 4.0% to 39.2%, protection against severe disease from 63.7% to 74.6%, and protection against death from 52.2% to 81.1%, depending on age group. During the two months after vaccination, the estimated effectiveness in preventing hospital and outpatient visits was 33.4%, while effectiveness in preventing hospitalization was 41.8%.
Choi Yoon-ho, deputy director of the Health Screening Center of the Korea Association of Health Promotion, Seoul Gangseo Branch, explained, "Vaccination is extremely important for preventing influenza, which is spreading rapidly. It typically takes about two weeks after vaccination for the body to develop sufficient antibodies. Since cases are increasing after already exceeding the epidemic threshold, vaccination needs to take place ahead of the speed at which the outbreak is spreading."
Children and adolescents, who are vulnerable to respiratory infectious diseases, as well as other high-risk groups should seriously consider vaccination. Early vaccination of children and adolescents not only helps prevent group infections in schools and childcare facilities, but also plays an important role in blocking secondary transmission to older adults and immunocompromised people at home.
High-risk groups with weaker immunity, including people aged 65 and older, those with chronic diseases, and pregnant women, face a high risk of developing serious complications such as pneumonia if infected with influenza. Simultaneous or sequential infection with influenza and COVID-19 can cause more severe symptoms than either infection alone and significantly increase the risk of serious complications.

This year's national immunization program will begin on September 21 for children and pregnant women, and on October 12 for older adults aged 65 and above, with those aged 75 and older vaccinated in stages. Starting this year, eligibility has been expanded to include children up to age 14, allowing adolescents previously excluded from the program to receive free vaccinations. People aged 65 and older will also receive COVID-19 vaccinations on the same schedule, and co-administration of the two vaccines is recommended.
Choi emphasized, "Preventing influenza infection and transmission requires active measures, including vaccination as well as stronger personal hygiene practices such as handwashing and wearing masks. In particular, high-risk groups—including children and adolescents, older adults, and pregnant women—should complete their vaccinations promptly according to the schedule before the outbreak fully takes hold." 

[email protected] Medical Specialist Reporter Jeong Myeong-jin Reporter