A multi-country cluster randomized controlled effectiveness evaluation to accelerate the introduction of Vi polysaccharide typhoid vaccine in developing countries in Asia: rationale and design
Phase-III vaccine efficacy trials typically employ individually randomized designs intended to ensure that measurements of vaccine protective efficacy reflect only direct vaccine effects. As a result, decisions about introducing newly licensed vaccines into public health programmes often fail to consider the substantially greater protection that may occur when a vaccine is deployed in public health programmes, due to the combination of direct plus indirect vaccine protective effects. Vaccine total protection can be better evaluated with cluster randomized trials. Such a design was considered to generate policy relevant data to accelerate the rationale introduction of the licensed typhoid fever Vi polysaccharide (PS) vaccine in Asia by the Diseases of the Most Impoverished (DOMI) typhoid fever programme. The DOMI's programme multi-country study is one of the largest cluster randomized vaccine trials ever mounted in Asia, which includes approximately 200 000 individuals. Its main objective is to determine the effectiveness of a licensed Vi PS vaccine. The rationale and design of this study are discussed. Preliminary results are presented that determined the final planning of the trial before immunization. Important methodological and practical issues regarding vaccine cluster randomized designs are illustrated.
Document Type: Research Article
Affiliations: 1: International Vaccine Institute, Seoul, South Korea 2: National Institute of Hygiene and Epidemiology, Hanoi, Vietnam 3: Guangxi Center for Disease Prevention and Control, Nanning, Guangxi, China 4: National Institute of Health Research and Development, Ministry of Health Republic of Indonesia, Indonesia 5: NAMRU-2, Jakarta, Indonesia 6: National Institute of Cholera and Enteric Diseases, Kolkata, India 7: Aga Khan University, Karachi, Pakistan 8: Research Policy and Cooperation, World Health Organization, Geneva, Switzerland 9: University of Western Ontario, Ont., Canada
Publication date: 01 December 2005