Abstract
To the Editor.—— We read with interest the recent article on typhoid vaccines by Schwartz et al.1We commend the authors for their intent to evaluate the efficacy of typhoid vaccination among travelers in developing countries; however, serious and important problems in methodology and analysis cast doubt on some of their conclusions. In this study, a case-exposure cohort study design2was used to estimate vaccine efficacy. The cases were ascertained via clinic-based surveillance, and the proportion of tourists vaccinated was estimated by a survey of clinic attendees. To use this study design to calculate vaccine efficacy, the following assumptions are needed: (1) vaccinated and unvaccinated ill tourists were equally likely to seek medical care at the study sites, and (2) the vaccination status of clinic patients was representative of the vaccination status of all tourists. No data were presented on the validity of these assumptions in this study,
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
