SMS versus telephone interviews for epidemiological data collection: feasibility study estimating influenza vaccination coverage in the Swedish population

This study compared the use of Short Message Service (SMS) on mobile phones and the use of telephone interviews in collecting self-reported data about influenza vaccination. Through random selection from the Swedish population registry, 2,400 individuals were assigned to be contacted through SMS (SMS-group), and 2,150 were assigned to undergo personal telephone interviews (TI-group). Both groups were asked three questions about influenza and influenza vaccination. Mobile phone numbers were found for 1,055 persons in the SMS-group of whom 154 (6% of the original sample; 15% of all who had a listed mobile phone number) responded. Landline or mobile phone numbers were found for 1,636 persons in the TI-group and 1,009 (47% of the original TI sample; 62% of those where a telephone number was found) responded. The vaccination data collected via SMS was not statistically significantly different from data collected through telephone interviews, and adjustment for different background factors did not change this. Compared to the original sample, there was an under representation of elderly and less educated individuals among the participants in the SMS-group, and under representation of less educated in the TI-group. Though the participation rate was low, SMS is a feasible method for collection of information on vaccination status data among the Swedish population compared to telephone interviews.