An epidemiological study on a varicella outbreak among initial entry trainees of the Sri Lankan Army and the cost-effectiveness of vaccinating susceptible individuals

Abstract

INTRODUCTION: Varicella which is a disease burden to the Sri Lankan Army. VZV immunization of susceptible recruits is limited due to its high cost and therefore, recommendation of vaccination should be evaluated from a cost effectiveness perspective. OBJECTIVE: To study : 1. Spread of a varicella outbreak among initial entry trainees. 2. Usefulness of taking the past history of varicella for screening of susceptible individuals. 3. Cost effectiveness of VZV vaccination of initial entry trainees of the Sri Lankan Army. DESIGN: A hospital based descriptive study conducted prospectively over a period of three months during an outbreak. SETTING: 682 initial entry trainees aged 18-24 years who entered the Volunteer Force Training School of the Sri Lankan Army, Diyatalawa on 21!d July 2002 from various parts of the country were enrolled in this study. They were either hospitalized for varicella at the Army Base Hospital or billeted in the Camp. METHODS: Details of the index, secondary and tertiary cases, and preventive and management measures carried out for varicella patients were recorded. The rate of contracting varicella amongst immune and non-immune recruits based on past history were analyzed. A sample of blood was collected from some patients for the serological confirmation of varicella and rubelSa. Cost effectiveness of VZV vaccination at the Sri Lankan Army Hospital was analyzed. RESULTS: 263 (38.6 %) of all new recruits had a past history of chicken pox and only 9 (3.4%) of them re-infected. A total of 271 recruits were hospitalized for chicken pox during the outbreak and 262 (96.7%) of them did not have a past history. In addition to the varicella, there was also clinical and serological evidence of an outbreak of rubella Vaccination of recruits was found to be cheaper (Rs. 4293.00 or US$ 43.00) compared to the cost of 14 days of hospital stay (Rs. 7265.00 or US$ 72.00). CONCLUSIONS: Hospitalization and treatment of patients with varicella in the Army Hospital found to be more costly compared to the vaccination of susceptible recruits against VZV. Past history of varicella will be useful to identify susceptible new recruits for VZV immunization. Proper isolation of the patients and segregation of susceptible individuals at the index and secondary case levels will minimise the spread.