MSD Korea's 15-valent pneumococcal vaccine shows strong immunogenicity in all serotypes

MSD Korea said Tuesday that “Vaxnuvance,” its 15-valent pneumococcal protein conjugate vaccine, best suits the first pneumococcal immunization of Korean infants and young children, citing its high preventive effectiveness and ability to induce an immune response.

The company said so at a news conference to highlight the characteristics of its product on Tuesday. MSD Korea first distributed the new vaccine to domestic hospitals and clinics in the first half of this year, and has resumed its promotion because pneumococcal vaccine sales are usually higher in the second half of the year. 

As higher-valent pneumococcal conjugate vaccines (PCVs) hit the U.S. pediatric market, the focus on assessing the quantity and quality of antibody responses has never been more crucial.

The World Health Organization (WHO) has issued standardized guidelines for assessing the immunogenicity of these vaccines. To prevent severe invasive pneumococcal disease (IPD) effectively, it is essential to evaluate not just the number of serotypes included but also the vaccine's ability to induce a robust immune response.

Against this backdrop, Vaxneuvance is the first new pneumococcal vaccine approved domestically in 13 years following the PCV13 launched in 2010. Vaxneuvance became a key component of Korea’s National Immunization Program for children when vaccinations began on April 1.

"Despite the addition of two new serotypes recognized globally as major culprits of invasive pneumonia and localized diseases, Vaxneuvance has demonstrated robust immunogenicity across all 15 serotypes," said Cho Jae-yong, executive director for vaccine business at MSD Korea, during the media event. "Especially notable is its superior performance against serotype 3, known for causing severe invasive diseases in children. This makes Vaxneuvance an outstanding choice as the initial pneumococcal vaccine in a child's life."

Pneumococcal disease continues to present a significant burden, particularly among young children. In 2023, around 50 percent of domestic patients treated for pneumococcal pneumonia were under five, with a five to 15 percent mortality rate for pneumococcal meningitis in this age group. Those who survive often face serious neurological sequelae, highlighting the pressing need for effective prevention.

The incidence of IPD is notably high in children under one year, with approximately half of all IPD cases in children under five occurring within the first year of life. Despite the drop in IPD cases following the introduction of PCV13, non-vaccine type (NVT) IPD has not decreased proportionately.

Globally, serotypes 3, 22F, and 33F are leading contributors to IPD, and both domestic and international data indicate that NVT IPD remains prevalent compared to the 13 serotypes covered by earlier vaccines. In Korea, the incidence of IPD among children under two nearly doubled from 2015 to 2019, underscoring the urgent need for enhanced preventive measures. 

"If a vaccine covered serotype 33F, it would be incredibly effective," said Professor Kang Hyun-mi of the Department of Pediatrics at the Catholic University of Korea Seoul St. Mary's Hospital. "The focus on serotypes 3, 22F, and 33F has been crucial in vaccine development, and maintaining immunogenicity against the original 13 serotypes is equally important."

The emphasis on certain pneumococcal serotypes stems from the fact that pneumococcus encompasses over 100 strains capable of causing disease. Covering all these serotypes in a vaccine isn’t feasible, so the goal is to include as many relevant ones as possible over time. However, research shows that as more serotypes are added to a vaccine, the immunogenicity against existing serotypes can diminish.

WHO defines immunogenicity as “the ability of a vaccine to induce a measurable immune response,” setting a benchmark for vaccine-induced serotype-specific immunoglobulin G (IgG) antibody levels at 0.35 µg/mL or higher.

"Despite incorporating two new serotypes, Vaxneuvance has achieved immunogenicity that meets or surpasses the WHO standard of 0.35 µg/mL for all 15 serotypes," Professor Kang said. “This achievement is notable because it counters the common issue known as "immunogenicity creep where adding more serotypes to a vaccine typically reduces its effectiveness against the original strains.” 

Professor Kang highly evaluated Vaxneuvance for its strong performance in clinical trials, noting that it “covers more serotypes than existing vaccines while demonstrating superior immunogenicity, particularly for serotypes 3, 22F, and 33F.” 

As a pediatrician, she emphasized that fundamental clinical study results are crucial in guiding vaccine choices, and with safety and efficacy confirmed in over 20,000 subjects, Vaxneuvance shows “non-inferior immunogenicity against the original 13 serotypes and strong responses to the additional ones."