Academic journal article Applied Health Economics and Health Policy

Burden and Cost of Hospital Admissions for Vaccine-Preventable Paediatric Pneumococcal Disease and Non-Typable Haemophilus Influenzae Otitis Media in New Zealand

Academic journal article Applied Health Economics and Health Policy

Burden and Cost of Hospital Admissions for Vaccine-Preventable Paediatric Pneumococcal Disease and Non-Typable Haemophilus Influenzae Otitis Media in New Zealand

Article excerpt

Introduction

Worldwide, Streptococcus pneumoniae (Sp.) is a leading cause of bacterial meningitis, bacteraemia, community-acquired bacterial pneumonia and acute otitis media (AOM), and is responsible for a considerable morbidity and mortality burden, particularly among young children and the elderly.[1-3] In several countries, the introduction of a pneumococcal conjugate vaccine into the infant immunization programme has resulted in a marked reduction in pneumococcal disease burden.[4-6] A 7-valent conjugate pneumococcal vaccine (PCV7) was introduced into the New Zealand (NZ) childhood immunization schedule for children born after 1 January 2008; however, local information is not yet available concerning the clinical or economic impact of this change. In clinical trials, PCV7 has been demonstrated to reduce invasive pneumococcal disease (IPD), pneumonia and otitis media in children aged <2 years.[7] Two novel pneumococcal conjugate vaccines have been developed and are under consideration for NZ; a 10-valent vaccine (PHiD-CV) and a 13-valent vaccine.[8,9] An 11-valent prototype to PHiD-CV was found to protect against otitis media caused by non-typable Haemophilus influenzae (NTHi).[10]

IPD is defined as isolation of Sp. from a normally sterile site, including blood and cerebrospinal fluid, and can present clinically as meningitis, bacteraemia, pneumonia and, more rarely, peritonitis, osteomyelitis and infective arthritis.[11,12] In NZ during 1998-2005, routine passive surveillance of laboratory isolates indicated an age-standardized annual incidence of IPD of 12.4 per 100 000 of the population. IPD occurred most frequently in children aged <2 years, in whom the average annual incidence was 101 per 100 000, while in all children aged <5 years it was 54.2 per 100 000.[12] Active surveillance in Auckland, NZ's largest city, during 1984-92 revealed significantly higher IPD incidences in Pacific Island and indigenous Maori children.[13] A recent meta-analysis of clinical trials showed that PCV7 reduces IPD from all serotypes by 74% and from vaccine serotypes by 89% in children aged <2 years.[7]

Sp. is the most prominent bacterium responsible for paediatric pneumonia cases and pneumonia deaths.[1,14,15] In NZ during 2002-6, pneumonia was responsible for 5% of all acute post-neonatal hospitalizations in children aged <15 years, with substantially higher admission rates observed for Pacific Island and indigenous Maori children.[16] A recent WHO meta-analysis of four clinical trials of conjugate pneumococcal vaccines in the pre-vaccination era estimated that 36% (95% CI 16, 51) of chest x-ray-confirmed pneumonia and 21% (95% CI 12, 29) of clinically diagnosed severe (hospitalized) pneumonia was caused by Sp. in children aged <5 years.[17] Each trial was adjusted for three factors: the proportion of pneumococcal disease caused by vaccine serotypes (based on serotypes causing IPD in the trial population); vaccine efficacy against vaccine-serotype pneumococcal disease; and the concurrent use of vaccine against H. influenzae type b (Hib).

In the US, after the introduction of universal immunization with PCV7 in 2000, all-cause pneumonia hospital admissions among children aged <2 years declined by 35% during 2006 in comparison with pre-vaccination years (1997-99).[18] This figure incorporates the direct effect of the vaccine and indirect effects (herd protection and serotype replacement). The role of NTHi in paediatric pneumonia in developed countries, if any, is equivocal.[19]

In developed countries, otitis media is the most common indication for antibacterial prescribing in young children.[20] Several studies have indicated that Sp. and NTHi are by far the most commonly implicated pathogens in AOM,[21-24] and cause clinically indistinguishable otological symptoms in children.[21,25] Hib infection has declined steeply in NZ since the early introduction of Hib immunization and is not considered further. …

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