Table 1.

Content of text messages sent to caregivers’ mobile phones.

Message type	Message timing	Arm 1: control	Arm 2: SMSa only	Arm 3: SMS+150 Kenyan Shilling
Enrollment message	Enrollment	Thank you for enrolling Baby <BABY’S FIRST NAME> in M-SIMIb study. The greatest wealth is health. This study is sponsored by KEMRIc.	Thank you for enrolling your child in the KEMRI M-SIMI study. You will get SMS reminders for Baby <BABY’S FIRST NAME>’s measles vaccination. The greatest wealth is health.	Thank you for enrolling your child in the KEMRI M-SIMI study. You will get SMS reminders for Baby <BABY’S FIRST NAME>’s measles vaccination. The greatest wealth is health.
3 day reminder message	Date of birth + 9 months – 3 days	No message	Tell Mama <BABY’S FIRST NAME> that Measles vaccine is due this week. Most Gem babies get vaccinated, be one of them!	Tell Mama <BABY’S FIRST NAME> that Measles vaccine is due this week. We are sending 150ksh to assist with travel. Most Gem babies get vaccinated, be one of them!
1 day reminder message	Date of birth + 9 months – 1 day	No message	Tell Mama <Baby Fname> that Measles vaccine is due this week. Go to the clinic if you haven’t already. Vaccines save Kenyan babies lives.	Tell Mama <Baby Fname> that Measles vaccine is due this week. Go to the clinic if you haven’t already. Vaccines save Kenyan babies lives.

^aSMS: short message service.

^bM-SIMI: Mobile and Scalable Innovations for Measles Immunizations.

^cKEMRI: Kenya Medical Research Institute.