Impact of 7- and 13-Valent PCVs on Pediatric Invasive Pneumococcal Disease in Singapore

Overview

This 24-year surveillance study from Singapore demonstrates a significant reduction in invasive pneumococcal disease (IPD) incidence among children, particularly those ≤2 years old, following the introduction of PCV7 and PCV13 into the National Childhood Immunisation Schedule. Despite overall declines, serotype 19A has emerged as a persistent cause of IPD post-PCV13 implementation.

Background

Streptococcus pneumoniae causes serious invasive diseases such as pneumonia, meningitis, and septicemia in children globally. Southeast Asia has one of the highest incidences of pneumococcal disease in children under 5 years. Pneumococcal conjugate vaccines (PCVs) target specific serotypes, but serotype replacement can occur, necessitating higher-valency vaccines. Singapore introduced PCV7 into its national immunization program in 2009, followed by PCV13 in 2011, aiming to reduce IPD burden in children.

Data Highlights

Key Findings

• The overall IPD incidence in children <17 years was 3.9 per 100,000 from 2000 to 2023.
• IPD incidence in children ≤2 years decreased significantly from 13.3 to 4.7 per 100,000 after PCV introduction (incidence rate ratio 0.4; P < .001).
• IPD cases caused by PCV7 serotypes declined markedly from 68.0% to 22.0% between periods 1 and 2 (OR 0.1; P < .001).
• IPD cases caused by PCV13 serotypes also decreased from 80.5% to 70.2% (OR 0.6; P = .03).
• The proportion of IPD due to serotype 19A increased significantly from 6.5% to 38.7% (OR 9.1; P < .001), indicating serotype replacement.
• No confirmed IPD cases were attributed to PCV15- or PCV20-specific non-PCV13 serotypes during the study period.

Clinical Implications

The introduction of PCV7 and PCV13 into Singapore's national immunization schedule has substantially reduced IPD burden in young children, especially those ≤2 years old. However, the rise of serotype 19A as a predominant cause of IPD highlights the need for ongoing surveillance and consideration of higher-valency vaccines to address serotype replacement. Clinicians should remain vigilant for IPD caused by emerging serotypes despite vaccination.

Conclusion

PCV implementation in Singapore has effectively decreased pediatric IPD incidence, but serotype 19A remains a significant challenge. Continued surveillance and vaccine strategy updates are essential to sustain IPD control.

References

1. Thoon et al 2024 -- The Burden of Invasive Pneumococcal Disease and the Effects of 7- and 13-Valent Pneumococcal Conjugate Vaccines in Singaporean Pediatric Population Over 24 Years