[Desk’s View] What’s next for NIP?

Korea has exceeded the 80% mark. In other words, most Koreans aged 65 and older are already vaccinated against influenza. With free vaccination being provided every year through the National Immunization Program (NIP), the program has made an impressive track record, at least in terms of vaccination coverage.

Having vaccinated so many people, it is now time to look at how well they are actually protected. Vaccination itself is not the goal. As the term suggests, the purpose is to “prevent” disease.

That is why influenza vaccination in older adults deserves a closer look. Age-related changes in the immune system, known as immunosenescence, can weaken immune responses to vaccination. Older adults are also more likely to have multiple chronic conditions, putting them at relatively greater risk of hospitalization, severe illness, and death following influenza infection.

In one study involving 8 university hospitals in Korea, influenza vaccine effectiveness among adults aged 65 and older during the 2023–2024 season was estimated at 13.5%. Results from a single season cannot be generalized to the entire older population, but they underscore the need to examine how much protection the current vaccination system actually provides.

However, 80% vaccination coverage and 13.5% effectiveness result cannot be directly compared. They measure different things and are calculated differently. Still, the contrast is hard to ignore

Enhanced influenza vaccines, including high-dose and adjuvanted vaccines, were developed with the weaker immune responses of older adults in mind. High-dose vaccines contain 4 times as much antigen as standard-dose vaccines to induce a stronger immune response. In a randomized trial involving about 32,000 adults aged 65 and older, a high-dose vaccine showed 24.2% greater relative efficacy against influenza than a standard-dose vaccine.

Other countries have already adopted approaches that take age and risk among older adults into account. The U.S. preferentially recommends high-dose, recombinant or adjuvanted influenza vaccines for adults aged 65 and older. Japan, after reviewing clinical utility and cost-effectiveness, plans to include high-dose influenza vaccination in its national immunization program for people aged 75 and older beginning this October.

Although the eligible ages and populations differ, these approaches share a common principle: public support begins with groups that need priority protection based on their level of risk. With phased introduction also under discussion in Korea, overseas cases could help inform decisions on priority groups and the direction of future expansion.

Related discussions are already underway in Korea. In its 2023 adult immunization recommendations, the Korean Society of Infectious Diseases recommended high-dose or adjuvanted influenza vaccines for adults aged 65 and older. More recently, the Korean Senior Citizens Association, medical groups and the National Assembly have raised the need for vaccination strategies that account for age and risk among older adults, as well as government support for high-immunogenicity vaccines.

The government has also begun reviewing the issue. At a National Assembly policy forum on innovative influenza prevention strategies for older adults in a super-aged society, Tong-ryoung Jung, director general for healthcare safety and prevention at the Korea Disease Control and Prevention Agency, recently said that “although there are some limitations in securing domestic data, the clinical superiority of high-immunogenicity vaccines is clear,” agreeing on the need to shift toward vaccines better suited to the diminished immune responses of older adults.

Ultimately, the issue comes down to funding. Clinical evidence alone cannot determine whether a new vaccine should be added to the NIP. Cost-effectiveness and fiscal capacity must also be considered, along with who should receive priority within a limited budget. If a phased introduction is pursued, what criteria should guide it? Beyond selecting priority groups, concrete discussions are also needed on when and how broadly eligibility should subsequently be expanded.

As noted, more than 8 in 10 older adults already receive influenza vaccination. But people aged 65 and older do not all face the same risks in terms of age, underlying conditions, or progression to severe disease after infection. Vaccination coverage alone cannot capture the level of protection across older adults with different risk profiles.

An 80% vaccination rate is a significant achievement for the NIP. With this milestone secured, it is time to focus on the next measure of success.