High nasopharyngeal carriage of non-vaccine serotypes in Western Australian aboriginal people following 10 years of pneumococcal conjugate vaccination.

Deirdre A Collins,Natalie A Stemberger,Peter C Richmond,Amanda J Leach,Jacinta Bowman,Anke Hoskins,Jade Jones,Deborah Lehmann,Eliane Namie Miyaji

doi:10.1371/journal.pone.0082280

Abstract

BackgroundInvasive pneumococcal disease (IPD) continues to occur at high rates among Australian Aboriginal people. The seven-valent pneumococcal conjugate vaccine (7vPCV) was given in a 2-4-6-month schedule from 2001, with a 23-valent pneumococcal polysaccharide vaccine (23vPPV) booster at 18 months, and replaced with 13vPCV in July 2011. Since carriage surveillance can supplement IPD surveillance, we have monitored pneumococcal carriage in western Australia (WA) since 2008 to assess the impact of the 10-year 7vPCV program. MethodsWe collected 1,500 nasopharyngeal specimens from Aboriginal people living in varied regions of WA from August 2008 until June 2011. Specimens were cultured on selective media. Pneumococcal isolates were serotyped by the quellung reaction. Results Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis were carried by 71.9%, 63.2% and 63.3% respectively of children <5 years of age, and 34.6%, 22.4% and 27.2% of people ≥5 years. Of 43 pneumococcal serotypes identified, the most common were 19A, 16F and 6C in children <5 years, and 15B, 34 and 22F in older people. 7vPCV serotypes accounted for 14.5% of all serotypeable isolates, 13vPCV for 32.4% and 23vPPV for 49.9%, with little variation across all age groups. Serotypes 1 and 12F were rarely identified, despite causing recent IPD outbreaks in WA. Complete penicillin resistance (MIC ≥2µg/ml) was found in 1.6% of serotype 19A (5.2%), 19F (4.9%) and 16F (3.2%) isolates and reduced penicillin susceptibility (MIC ≥0.125µg/ml) in 24.9% of isolates, particularly 19F (92.7%), 19A (41.3%), 16F (29.0%). Multi-resistance to cotrimoxazole, tetracycline and erythromycin was found in 83.0% of 23F isolates. Among non-serotypeable isolates 76.0% had reduced susceptibility and 4.0% showed complete resistance to penicillin.ConclusionsTen years after introduction of 7vPCV for Aboriginal Australian children, 7vPCV serotypes account for a small proportion of carried pneumococci. A large proportion of circulating serotypes are not covered by any currently licensed vaccine.

Highlights

Invasive pneumococcal disease (IPD), which includes pneumonia, meningitis, and septicaemia, causes an estimated 476,000 deaths in children < 5 years annually, the majority of which occur in the third world [1]
Proportion of pneumococcal carriage serotypes covered by different vaccine formulations Overall, we found 14.5% of serotypeable pneumococci were 7vPCV serotypes, equivalent to a prevalence of 7.0%. 13vPCV would have covered 32.4% of serotypes carried during the study period across all ages
This is the first assessment of pneumococcal carriage in Aboriginal people in western Australia (WA) in the PCV era

Summary

Introduction

Invasive pneumococcal disease (IPD), which includes pneumonia, meningitis, and septicaemia, causes an estimated 476,000 deaths in children < 5 years annually, the majority of which occur in the third world [1]. A booster of 23-valent pneumococcal polysaccharide vaccine (23vPPV, Pneumovax 23®, covers 7vPCV serotypes and 1, 2, 3, 5, 7F, 8, 9N, 10A, 11A, 12F, 15B, 17F, 19A, 20, 22F and 23F) was offered at age 18 months to Aboriginal children. Since the introduction of 7vPCV, the incidence of IPD caused by vaccine serotypes has fallen but IPD due to non-7vPCV serotypes has increased, and almost doubled in WA Aboriginal adults aged 30-49 years [2]. Invasive pneumococcal disease (IPD) continues to occur at high rates among Australian Aboriginal people. Since carriage surveillance can supplement IPD surveillance, we have monitored pneumococcal carriage in western Australia (WA) since 2008 to assess the impact of the 10-year 7vPCV program. Conclusions: Ten years after introduction of 7vPCV for Aboriginal Australian children, 7vPCV serotypes account for a small proportion of carried pneumococci. A large proportion of circulating serotypes are not covered by any currently licensed vaccine

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