Invasive pneumococcal disease in Australia, 2011 and 2012

Area of Science:

• Public Health
• Epidemiology
• Vaccinology

Background:

• Invasive pneumococcal disease (IPD) remains a significant public health concern in Australia, disproportionately affecting Indigenous populations.
• Surveillance data from the National Notifiable Diseases Surveillance System (NNDSS) tracks IPD incidence and trends.
• Pneumococcal vaccines, including the 13-valent pneumococcal conjugate vaccine (13vPCV) and the 23-valent pneumococcal polysaccharide vaccine (23vPPV), are key interventions.

Observation:

• In 2011 and 2012, Australia reported substantial numbers of IPD cases, with overall rates significantly higher in Indigenous Australians compared to non-Indigenous Australians.
• Following the 13vPCV introduction in July 2011, a notable decrease in IPD rates was observed in children under five years.
• Conversely, IPD rates caused by serotypes targeted by the 23vPPV showed an increasing trend in Indigenous adults aged 50 years and over, and non-Indigenous adults aged 65 years and over.

Findings:

• The 13vPCV vaccine demonstrated effectiveness in reducing IPD incidence among young children.
• Increasing IPD rates in specific adult populations, particularly Indigenous adults, highlight ongoing challenges and potential gaps in vaccine-induced protection or serotype replacement.
• Antimicrobial resistance, specifically reduced penicillin susceptibility and rare ceftriaxone/cefotaxime resistance, remained low in invasive pneumococcal isolates.

Implications:

• The findings underscore the importance of continued surveillance and targeted vaccination strategies to address the persistent burden of IPD, especially in vulnerable populations.
• Further research is needed to understand the drivers of increasing IPD rates in older adults and to evaluate the long-term impact of 13vPCV on serotype distribution and potential serotype replacement.
• Maintaining low levels of antibiotic resistance is crucial for effective treatment of IPD, necessitating ongoing monitoring and prudent antibiotic stewardship.