Background: Background: Latina adolescents report low levels of moderate-vigorous physical activity (MVPA) and high lifetime risk of lifestyle-related diseases. There is a lack of MVPA interventions targeted at this demographic despite documented health disparities. Given their high rates of using mobile technology, interventions delivered through mobile devices may be effective for this population. Objective: Objective: The current paper examines efficacy of the Chicas Fuertes intervention in increasing MVPA across six months in Latina adolescents. Methods: Methods: Participants were Latina adolescents (ages 13-18) in San Diego County who reported being underactive (<150 minutes/week of MVPA). All participants received a wearable fitness tracker (Fitbit Inspire HR); half were randomly assigned to also receive the multimedia intervention. Intervention components included a personally tailored website, personalized texting based on Fitbit data, and social media. The primary outcome was change in minutes of weekly MVPA from baseline to six months (6m), measured by ActiGraph accelerometers and the 7-Day Physical Activity Recall Interview. Changes in daily steps using Fitbit devices were also examined to test intervention efficacy. Results: Results: Participants (N=160) were 15.3 years old on average, and mostly second generation in the U.S. For ActiGraph-measured MVPA, participants in the Intervention group (N=83) increased from a median of 0 min/week at baseline (IQR 26) to 64 min/week at 6m (IQR 28) compared to Control participants, who showed increases from a median of 0 at baseline (IQR 24) to 41 min/week at 6m (IQR 21) (P=.04). Self-reported MVPA increased in the Intervention group from a median of 119 min/week at baseline (IQR 122.5) to 147 min/week at 6m (IQR 85) compared to Control participants, who showed increases from a median of 120 (IQR 186.25) at baseline to 124 min/week at 6m (IQR 69) (P=.03). Steps also increased in both groups, with the Intervention group showing significantly greater increases (P=.03). Conclusions: Conclusions: This intervention was successful in using a tailored technology-based strategy to increase MVPA in Latina adolescents and provides a promising approach for addressing a key health behavior. Given the scalable technology used, future studies should focus on broad scale dissemination to address health disparities. Clinical Trial: ClinicalTrials.gov NCT04190225; https://clinicaltrials.gov/study/NCT04190225?id=NCT04190225

Background: The global, nearly universal penetration of mobile phones has offered novel opportunities for delivering health services and communicating health-related information to individuals. A low-cost system that facilitates autonomous communication with individuals via mobile phones holds potential for expanding the reach of health messaging and service delivery in settings with human resource and infrastructure limitations. Objective: We sought to design a flexible, low-code system using open-source software that could be adapted to different contexts and technical environments and accommodate a wide range of automation needs. We report on key details of the mobile phone-based appointment reminder and incentive system (mParis), document its use, review implementation challenges and adaptations to address these challenges in the context of a quasi-randomized trial of mobile phone-based reminders and incentives as means of increasing the timeliness of routine childhood vaccinations in Tanzania, and outline other use cases that highlight the versatility of the system. Methods: The mParis instance described in this manuscript, which is hosted in Tanzania, sent automated, individualized vaccination reminders to the mobile phones of mothers of young children. Process workflows, based on the national childhood vaccination schedule of Tanzania, were programmed into mParis. Reminders for vaccinations due at ages 6, 10, and 14 weeks were sent 7 days and 1 day prior to and 14 days after each vaccination due date. A subset of messages included financial incentive offers to mothers for the timely vaccination of their children. We report on implementation outcomes, challenges, and adaptations to address these challenges. Results: Between August and December 2017, 412 pregnant women were enrolled into the trial. After mothers reported the birth of their children, individualized vaccination reminder messages were sent for vaccination due dates between January and July 2018. From March 2018, messages contained financial incentive offers. Of 1,397 messages sent, 1,122 SMS (80.3%) were recorded as delivered, 249 (18.8%) as expired and resent, 23 (1.6%) as failed, and 3 (0.2%) as sent but lacking delivery confirmation. 633 messages (45.3%) contained tiered incentive offers. Of 173 women who received at least one message, 67 (38.7%) were sent reminders only; 106 women (61.3%) were sent at least one incentivized message. Numerous challenges were encountered during the system’s implementation, despite its deliberate design to accommodate basic problems such as intermittent internet access and power failures. Continuous adaptation to increase the resilience of the system, complemented by limited backstops, resulted in a successful deployment. Conclusions: mParis’ open-source nature, auditability, and ability to autonomously execute algorithms in a low-resource setting with frequent infrastructure challenges suggest favorable prospects to automate health communication in a wide range of settings. mParis’ use in multiple other health-related research studies demonstrates its versatility and ability to accommodate challenges that may be encountered in diverse other contexts. Clinical Trial: ClinicalTrials.gov: NCT03252288