In 1974, WHO (World Health Organization) instituted the Expanded Program on Immunization (EPI). EPIs' objective is to vaccinate all children under 1 year of age against 6 diseases (Tuberculosis, Diphtheria, Tetanus, Poliomyelitis, Whooping Cough and Measles). EPI thus became a major component of the health systems, particularly in Developing Countries. One of the most popular methods used to evaluate EPI consists in performing a cluster sampled survey, using a simplified method developed and recommended by WHO. Such survey mainly allow the calculation of vaccine coverage rates, which are used to measure how the evaluated program works, or to compare different programs.
COSAS has been developed on WHO's request. This PC software is designed to ease the analysis of data collected, and to standardize this analysis, in a way to allow comparison among different immunization programs. It works on any IBM-PC compatible under Windows® 9x. It doesn't require specific computer knowledge. The user is guided by menus. Data entry can be parameterized and can adapt to different situations. Context sensitive help may be obtained at any time.
During data entry, COSAS checks the validity of data collected. It can then produce immunization coverage rates before 1 year of age, according to the immunization card, or according to history (what the Mother says). These rates are global indicators which allow to monitor how the program works globally, and to make an estimate of its impact. Moreover, Information technology allow the calculation of more specific indicators, such as
- proportion of never-vaccinated children (program coverage),
- proportion of invalid doses (respect of the schedule),
- 'drop-out' rate (mothers' motivation),
- average interval between 2 boosters (Organization of the session),
- mean age at immunization (capacity of the program to reach children the earliest possible),
- distribution of the vaccines administration dates (regularity of the program),
- proportion of missed opportunities (knowledge of the schedule and of contra-indications).
- When necessary, results may be displayed as graphics.
Some of the indicators calculated by the software were already widely uses, others bring informations that were rarely available. It has to be kept in mind that, as it is surveys, results have to be surrounded by a confidence interval. This one can be wide, as it is the case for indicators that are calculated on a part of the sample.
When cautiously interpreted, the extra informations obtained during the survey may lead to a better knowledge of the EPI, and should allow to upgrade it.
Originally developped on DOS, the new COSAS version is now running on Windows(R). It has been developped in collaboration with MSH (Management Sciences for Health) and IOCHP (Bangladesh Immunization and other child program) thanks to a USAID grant.
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