Review
How best to estimate the global burden of pertussis?

https://doi.org/10.1016/S1473-3099(03)00669-8Get rights and content

Summary

In most countries, pertussis surveillance is inadequate for accurately estimating numbers of cases or deaths. Good estimates are needed to help set priorities for vaccination programmes. We aimed to develop a simple, reliable, and explicit method for estimating pertussis cases and deaths for children under 15 years to calculate the global disease burden in 1999. We estimated the proportion of susceptible children becoming infected in countries with poor vaccination coverage (< 70%) in 1999 at 30% by 1 year, 80% by 5 years, and 100% by 15 years of age and for countries with good coverage (≥70%) at 10% by 1 year, 60% by 5 years, and 100% by 15 years. Vaccine efficacy was estimated at 80% for preventing infection and 95% for preventing deaths. We used UN population estimates and vaccination coverage reported to WHO (adjusted for specific survey data if available). Case fatality ratios for countries with high and low child mortality were derived from published and unpublished work. For some countries with good vital events registration we used reported deaths adjusted for underascertainment. In 1999 there were an estimated 48-5 million pertussis cases in children worldwide. Deaths from pertussis were estimated at 390 000 and at 295 000 after adjustment for local data sources. Based on this approach, disability-adjusted life years from pertussis (12·7 million) in 2000 exceeded those of other preventable diseases such as lung cancer (11·4 million) and meningitis (5·8 million). This simple approach yields estimates that can be used for setting vaccination programme priorities. Better data are needed on the public health importance of pertussis in high mortality countries, the benefits of incomplete vaccination, and the harm from delayed vaccination.

Section snippets

Background

The WHO produces the World Health Report to help set national and international priorities in health.1 Such a report creates a challenge with respect to pertussis. In most countries in the world, surveillance systems, even good ones, underestimate the number of pertussis cases and deaths from pertussis.2 Consequently, pertussis is not perceived to be a significant health problem in many countries. Pertussis is one of the diseases for which the WHO and national authorities need good information

Methods

Our starting point for the methods was the approach taken by Galazka3 for previous global estimates. The evidence base for some of the parameters used by Galazka had not been fully described, and we made use of further evidence that has accumulated since Galazka developed his method. For the Global Burden of Disease report, WHO requires numbers of pertussis cases and deaths by age and country. Relevant age groups for pertussis in children were under 1 year, 1–4 years, and 5-14 years. Reliable

Results

In 1999 there were an estimated 48·5 million pertussis cases in the world (table 3). Deaths from pertussis were estimated at 390 000 by the model, reduced to 295 000 after adjustment for the envelope and the cause-of-death analysis described above. Cases in the African Region accounted for 26·3% of the total (in 15·7% of the world's children under 15 years), and in the South East Asian Region for 25·7% of all cases (in 27·6% of the world's children under 15 years). Although the estimated CFR is

Discussion

This simple approach yields estimates that are suitable for setting global and regional vaccination programme priorities. The results do not differ greatly from those obtained by Galazka but the basis for the parameters is more explicit, and we have identified the priorities for improving the evidence base. The approach can be modified in future as more information becomes routinely available.

Comparing case numbers with UK notifications and adjusting for underascertainment, the model still

Search strategy and selection criteria

Articles were obtained through an extensive review of published and unpublished material. We did a Medline search of articles on pertussis complications, epidemiology, mortality, prevention, and control and transmission published since 1966. The articles were then searched to limit them to those yielding mortality estimates before obtaining and quality assessing the articles. WHO regional office databases and hand searches of EPI literature and other collections of literature were done without

References (63)

  • ME Ramsay et al.

    Age-specific efficacy of pertussis vaccine during epidemic and non-epidemic periods

    Epidemiol Infect

    (1993)
  • CC Dauer

    Reported whooping cough morbidity and mortality in the United States

    Public Health Reports

    (1943)
  • JA Clarkson et al.

    The efficiency of measles and pertussis notification in England and Wales

    Int J Epidemiol

    (1985)
  • JD Cherry

    Comparative efficacy of acellular pertussis vaccines: an analysis of recent trials

    Pediatr Infect Dis J

    (1997)
  • World population prospects: the 2000 revision, selected indicators by single calendar year, major area, region and country, 1970-2010. POP/DB/WPP/ Rev. 2000/SP.2

    (2000)
  • WHO vaccine preventable diseases monitoring system. 2000 global summary. WHO/V&B/00·32

    (2000)
  • NJ Binkin et al.

    Epidemiology of pertussis in a developed country with low vaccination coverage: the Italian experience

    Pediatr Infect Disease J

    (1992)
  • E Lu et al.

    Pertussis in Arkansas

    JArk Med Soc

    (1996)
  • RC Begg

    Pertussis–New Zealand 1982/83

    NZ Med J

    (1984)
  • KM Farizo et al.

    Epidemiological features of pertussis in the United States, 1980-1989

    Clin InfectDis

    (1992)
  • D Guris et al.

    Changing epidemiology of pertussis in the United States: increasing reported incidence among adolescents and adults, 1990-1996

    Clin Infect Dis

    (1999)
  • W Scheil et al.

    Pertussis in South Australia 1893 to 1996

    Commun Dis Intell

    (1998)
  • HC Matter

    Sentinella Arbeitsgemeinschaft. Pertussis surveillance in Switzerland, 1992 to 1997–a large epidemic in 1994. What next?

    Euro Surveillance

    (1999)
  • Surveillance of adverse events following immunisation (AEFI)–pertussis outbreak in North Batinah surveillance report

    (1997)
  • Pertussis–Washington, 1984

    MMWR Morb Mortal Wkly Rep

    (1985)
  • V Romanus et al.

    Pertussis in Sweden after the cessation of general immunization in 1979

    Pediatr Infect Dis J

    (1987)
  • B Trollfors et al.

    A placebo-controlled trial of a pertussis-toxoid vaccine

    N Engl J Med

    (1995)
  • Pertussis–United States, January 1992-June 1995

    MMWR Morb Mortal Wkly Rep

    (1995)
  • F Milord

    Resurgence of pertussis in Monteregie, Quebec–1990-1994

    Can Commun Dis Rep

    (1995)
  • A Nielsen et al.

    Epidemiology of pertussis in Denmark: the impact of herd immunity

    Int J Epidemiol

    (1994)
  • Resurgence of pertussis–United States, 1993

    MMWR Morb Mortal Wkly Rep

    (1993)
  • Cited by (0)

    View full text