public static ImmunizationFactory getInstance()
        {
            if (ImmunizationFactory.immunizationFactoryInstance == null)
            {
                immunizationFactoryInstance = new ImmunizationFactory();
            }

            return(immunizationFactoryInstance);
        }
 private ImmunizationFactory()
 {
     ImmunizationFactory.immunizationFactoryInstance = null;
 }