Isoniazid preventive therapy (IPT) reduces the risk of tuberculosis in 60%. Young children are at higher risk of developing severe forms of TB, though this can be prevented with a full course of IPT. Preliminary data indicate that 60% of eligible children start IPT, and 30% complete it. Furthermore, children can be exposed to more than one case of TB in the household. Adults exposed to TB in the household setting are not necessarily aware of their risk. Uncertainties in the decisions of staff to prescribe IPT and limited health literacy among caretakers and families contribute to this. The investigators will determine the efficacy of an intervention package to increase IPT adherence and completion among children < 5 years old exposed to TB in the household. The investigators will assess the efficacy of the intervention by 1) measuring IPT completion at 6 months after treatment initiation and by 2) determining adherence to IPT by measuring isoniazid in urine at weeks 2, 8 and 24 in a random cluster sample of 10 health facilities and 20 control facilities with 10 children included in each facility (100 in intervention and 200 in control). The investigators will measure fidelity and reach, and acceptability among caretakers and health staff. The intervention package will consist of: 1) educational booklet for caretakers explaining why IPT needs to be given 2) a children's storybook, with weekly installments, over the 6-month course of IPT as a non-monetary incentive and 3) short messages services (SMS) reminders delivered to the caretaker for the weekly pick-up

In September 2020, the protocol was updated to adapt to the COVID19 situation in Lima. One of the secondary outcome (isoniazid concentration in urine) was cancelled and the full intervention (educational booklet, weekly children storybook and weekly SMS) is now delivered through WhatsApp.

A cluster randomized study was designed, randomizing 10 health facilities to the intervention arm and 20 to control arm. In each, 10 children will be recruited. The mother, or the main caretaker in the intervention arm will receive the intervention package: 1) an educational booklet indicating the importance of IPT, adherence to IPT as well as information on how to give it daily for six months. Thereafter, the mother or main caretaker receives 2) a chapter of a children storybook delivered weekly and 3) SMS to remind her of the pick up, as well as weekly SMS containing a motivating message. Until March 2020, component 1 and 2 of the intervention package were delivered in person, since September 2020 and in adaptation to the SARS Cov2 pandemic, these are delivered via WhatsApp. Children in the control arm will receive the standard of care which consists of a advice and counseling given by the doctor and nurse at the health facility.

The investigators will assess the efficacy of the intervention by 1) measuring IPT completion at 6 months after treatment initiation. The secondary outcome originally planned (determining adherence to IPT by measuring isoniazid in urine at weeks 2, 8 and 24) has been cancelled in adaptation to the SARS Cov2 pandemic.

Fidelity, reach and acceptability will be measured among caretakers and staff with an in depth interview at the end of the study.

Inclusion Criteria:

• Caretakers of a child who is 1) < 5 years old 2) contact of a TB patient 3) has an IPT prescription from the TB physician and 4) has a smartphone that can use WhatsApp to receive the intervention.

Exclusion Criteria:

• Caretaker does not want to participate or cannot provide consent

All study data can be shared with other researcher for research purposes as allowed in the IRB application.

Upon completion of the study, for five years.

Individual patient data will be submitted by the PI (Larissa Otero) upon request by other researchers.