Higher Number Isn't Always Better: The Hidden Truth About Pneumococcal Vaccines

"I heard she was hospitalized with pneumonia—she's lost so much weight."

"They say it would have been worse without the vaccine. You did get yours, right?"

I couldn't help overhearing this conversation among elderly passengers on the subway. As a biotech reporter, the word "vaccine" naturally caught my attention.

Since Barbie Hsu (48), the famous Taiwanese actress and wife of singer Koo Jun-yup of the group Clon, died last year from pneumonia complications following influenza, fear of pneumonia has gripped Korea's elderly population.

Pneumonia is the third leading cause of death in Korea, behind cancer and heart disease. Even those under 65 face 3 to 9.8 times higher risk of pneumococcal pneumonia if they have diabetes or chronic heart or lung disease. Cancer patients face up to 12.5 times greater risk.

As both incidence and fatality rates rise with age, the Korean Society of Infectious Diseases recommends vaccination for adults 65 and older. Pneumococcus, responsible for approximately 69% of bacterial pneumonia cases, is preventable through vaccination.

The Number Trap

When choosing a vaccine, the numbers and price differences can be confusing.

The 23-valent polysaccharide vaccine (PPSV23), available in Korea since 1991, is covered under the national immunization program. Adults 65 and older with no prior vaccination can receive it free. The "N-valent" designation indicates how many pneumococcal serotypes the vaccine protects against. With over 90 known serotypes, pharmaceutical companies select the most infectious strains for their vaccines.

Protein conjugate vaccines (PCVs), containing 13 to 21 antigens depending on the product, are not covered by the national program. Prevnar 20, which protects against 20 serotypes, costs 110,000 to 160,000 won. Capvaxive, launched in Korea this month with 21 serotypes—the most among approved PCVs—costs 150,000 to 200,000 won.

Why Fewer Serotypes Cost More

Here's the puzzle: if more serotypes mean broader protection, why is the free 23-valent vaccine cheaper than PCVs with fewer serotypes?

The answer lies in how each vaccine activates the immune system.

PPSV23, based on polysaccharide antigens from bacterial cell walls, stimulates only B cells in a T-cell-independent immune response. It produces antibodies but fails to create immunological memory. Despite broader serotype coverage, protection may wane over time.

PCVs combine polysaccharide antigens with carrier proteins, triggering T-cell-dependent immune responses. This generates robust antibodies and immunological memory, providing longer-lasting protection from a single dose.

Calls for Policy Change

Infectious disease experts argue the government should subsidize PCVs, which offer superior pneumonia prevention in both children and adults. They contend the current policy supporting only older vaccine technology cannot adequately protect the elderly. Concerns also exist that income-based disparities in vaccination rates could create equity issues.

Consumers should look beyond the numbers and evaluate vaccine quality based on immune response.

For those paying out of pocket, prices vary widely between hospitals. Consumers can compare non-covered vaccine prices across medical institutions through the Health Insurance Review and Assessment Service website or the mobile app "Health e-eum."