From 10-Valent to 21-Valent Pneumococcal Conjugate Vaccines: Divergent Global Pathways and Future Directions for India.

Pneumococcal conjugate vaccines (PCVs) have greatly reduced invasive pneumococcal disease worldwide, though outcomes vary with the serotype formulation and regional context. India's introduction of indigenous 10-valent PCV into its Universal Immunization Program (UIP) was a major milestone, differing from the earlier globally available PCV10 by including serotypes 19A and 6A-both of which have been linked to antimicrobial resistance (AMR) in countries such as Belgium and Brazil. This review synthesizes global vaccine experiences, explores serotype biology, cross-protection, and the emergence of non-vaccine types, and considers the spectrum of higher-valency options (PCV14, PCV20, and PCV21). India's pediatric PCV coverage has expanded rapidly, though unevenly, while adult uptake remains limited. While indigenous PCV10 introduction and scale-up, followed by indigenous PCV14 introduction seems a pragmatic policy for India's UIP today, sustained genomic and AMR surveillance, plus eventual transitions to broader PCVs, will be essential for long-term, adaptable immunization strategies.