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PubMed · 8569019

Evaluating new vaccines for developing countries. Efficacy or effectiveness?

J Clemens·R Brenner·M Rao·N Tafari·C Lowe
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Abstract

Despite the profusion of promising new vaccines against illnesses prevalent in developing countries, uncertainties about the balance between costs and benefits of new vaccines have retarded their use in public health practice. Conventional prelicensure trials of vaccine protection exacerbate these uncertainties by focusing on measurement of vaccine efficacy--the performance of a vaccine under idealized conditions. Vaccine effectiveness trials provide a more pragmatic perspective by addressing the performance of a vaccine under the ordinary conditions of a public health program, by capturing direct as well as indirect effects of vaccination, and by comprehensively addressing outcomes of public health concern. The use of effectiveness trials should enable more rational triaging of new vaccines for developing countries and may accelerate the introduction of new vaccines into public health practice by resolving speculative debates about practical costs and benefits.

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Case-Control StudiesClinical Trials as TopicClinical Trials, Phase IV as TopicCohort StudiesCommunicable Disease ControlDeveloping CountriesDrugs, InvestigationalHumansPolicy MakingResearch DesignVaccinationVaccinesJournal Article

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J Clemens, R Brenner, M Rao, N Tafari, C Lowe. 1996-02-07. Evaluating new vaccines for developing countries. Efficacy or effectiveness?. https://pubmed.ncbi.nlm.nih.gov/8569019/

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PubMed1997

High-dose pancreatic-enzyme supplements and fibrosing colonopathy in children with cystic fibrosis.

BACKGROUND: Fibrosing colonopathy has been reported in young children with cystic fibrosis, the majority of whom take high-strength pancreatic-enzyme supplements to control intestinal malabsorption. We conducted a case-control study in the United States to investigate the relation between dose and type of pancreatic-enzyme supplement and fibrosing colonopathy. METHODS: Children with histopathologically confirmed cases of fibrosing colonopathy who required colectomy for colonic strictures from January 1, 1990, through December 31, 1994, were identified. Each of these patients was matched according to age at the time of surgery and medical center with up to four controls with cystic fibrosis who did not have fibrosing colonopathy. RESULTS: We studied 29 patients (mean age, 5.0 years) with fibrosing colonopathy (case patients) and 105 controls (mean age, 5.2 years). The mean dose of pancreatic-enzyme supplement was 50,046 units of lipase per kilogram of body weight per day for the case patients and 18,985 units per kilogram per day for the controls. A history of gastrointestinal complications attributed to cystic fibrosis and the use of histamine H2-receptor blockers, corticosteroids, or recombinant human DNase (dornase alfa) were associated with a higher incidence of fibrosing colonopathy. After adjustment for a history of such complications and the use of these medicines, the relative risk of fibrosing colonopathy that was associated with a dose of 24,001 to 50,000 units of lipase per kilogram per day, as compared with a dose of 0 to 24,000 units per kilogram per day, was 10.9 (95 percent confidence interval, 1.6 to 71.8), and that associated with a dose of more than 50,000 units per kilogram per day was 199.5 (95 percent confidence interval, 9.9 to 4026.0). The strength, coating, and manufacturer of the products used were not associated with the risk of fibrosing colonopathy. CONCLUSIONS: In young children with cystic fibrosis, we found a strong relation between high daily doses of pancreatic-enzyme supplements and the development of fibrosing colonopathy. Our findings support recommendations that the daily dose of pancreatic enzymes for most patients should remain below 10,000 units of lipase per kilogram.

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