. Roth and colleagues (2009) found no differ ence between cases and control subjects in prevalence of vitamin D insufficiency in Canada. In contrast, Ways and colleagues (2004) found adequate serum vitamin D to be associated with a lower risk of ALRI in India. Roth and colleagues (2009) suggested that the causative agent might explain the difference in findings between their study and the study by Wayne and associates (2004), noting that bacterial pneumonia is common in developing countries like India, but the study by Roth and associates (2009) in Canada included mostly patients with viral ALRI. Vitamin D might have a different effect on bacterial versus viral ALRI