INTRODUCTION: There is an increasing interest and funding for the use of Information and Communication Technologies in the field of health. However, studies have shown conflicting results of Short Messaging Service (SMS) or Text reminder in the improvement of health care services such as immunization. This paper aims to determine the effect of SMS reminder on the immunization rate, which includes the dropout, delayed and prompt immunization rate. METHODS: Newly registered children for immunization at Barangay Pinyahan Health Center were enrolled in randomized controlled double blind field trial. 144 subjects were exposed to treatment 1 (regular follow-up with no SMS reminder; treatment 2 (with SMS reminder); and treatment 3 (with blank SMS reminder). Immunization rate which included dropout, delayed and prompt immunization rates were determined. The effects of the confounding factors such as family income, barangay location, and number of children, parental education and immunization status of siblings were also determined. RESULTS: The prompt immunization rate is inversely proportional to the dropout and delayed immunization rates. As the subjects progress to the third dose of the immunization, the dropout rate increases. The dropout rate is highest on the third dose of Hepatitis B and Measles vaccination which are given at a later age of a child. Only 6% of the total subjects were classified as Fully Immunized Child. This data is in contrast to the national data of Fully Immunized Child coverage at 80%. SMS reminder has no significant effect on the immunization rate for DPT, OPV, HPV and Measles in Barangay Pinyahan Health Center in comparison to the regular follow-up. However, in Treatment Group 3 (SMS Reminder), the dropout rates per type of vaccine are significantly different from each other. The dropout of DPT and OPV which is expected to be equal or higher than Hepatitis B and Measles vaccine is lower. Variation in immunization rates among different income groups and geographic barangay location is particularly evident. Low income families and living distant from the health center have a significant propensity to dropout from immunization. CONCLUSION SMS reminder and regular follow-up have no significant difference on the immunization rate. Information communications technologies such as SMS reminder are more likely to affect immunization rate when health systems offer a supportive environment of consistently available vaccine such as DPT and OPV, and confounding barriers such as low family income, which affects HPV immunization rate, and distance to the health center, which affects measles immunization rate, are at the minimum.