Compliance to live oral Ty21a typhoid vaccine, and its effect on viability

Background: Concerns have been expressed that in travelers the efficacy of the live oral Ty21a typhoid vaccine Vivotif (R) could be lower than reporte d, maybe due to a lack of compliance. The purpose of this study was to exam ine the level of compliance with the recommendations regarding dosing, timi ng of dosing with respect to food intake, and storage. Method: Travelers were randomized into two groups: one received oral inform ation only, and the second, a combination of oral and written information. Four criteria of compliance were applied to travelers: 3 capsules needed to be swallowed (criterion 1) on day 1,3 and 5 (criterion 2), at least 1 hour before or 2 hours after a meal (criterion 3) and the vaccine had to be kep t refrigerated (2-8 degreesC) (criterion 4). Compliance was evaluated using three different methods: a questionnaire, pill counting, and electronic mo nitoring using the Medication Event Monitoring System (MEMS (R)). Storage c onditions were checked by temperature tags, and viability of the vaccine wa s assessed by culturing the content of remaining capsules. Results: The data of 115 travelers were analyzed. All the travelers took th e 3 capsules. Compliance to all four criteria was complete in 68% of travel ers according to the questionnaire, and 53% according to the MEMS (p = .05) . Sixty-seven per cent of all the doses intervals were of 48 hours +/- 6 ho urs, 12% being shorter than 36 hours and 7% longer than 60 hours. Eighty-se ven travelers (76%) took their capsules on each alternate day. The method o f information had no significant impact on compliance. Forty-two percent of tags showed exposure to temperature over 10 degreesC for more than 24 hour s. Yet, no difference could be found in the viability of the vaccine compar ed with controls. Conclusions: Most travelers take their 3 capsules on alternate days, but ma ny did not follow the other recommendations. Electronic monitoring of compl iance provides more accurate results than questionnaires. Emphasis must be put on motivating the travelers to take the vaccine as recommended.