Feasibility of implementing a cellphone-based reminder/recall strategy to improve childhood routine immunization in a low-resource setting: a descriptive report

The aim of the study was to determine the feasibility of implementing a cellphone-based reminder/recall intervention designed to improve routine childhood immunization compliance (measured as the percentage of children correctly following immunization schedule) and coverage (measured as the percentage of fully-immunized infants) among infants in four local government areas (LGAs) in Ibadan, Oyo State, Nigeria.

In this study, the term ‘feasibility’ was used to capture the following elements: (1) Acceptability of childhood immunization reminder/recall system (mothers’ willingness to receive cellphone reminders and recalls); (2) Adaptability or practicability of implementing a childhood immunization reminder/recall intervention in PHC facilities without immunization registries or immunization information system; (3) Effectiveness of immunization reminder/recall system (the extent to which cellphone immunization reminder/recall intervention increases immunization compliance at PHC level in a low resource setting).

Ibadan is located in the south western part of Nigeria. It is the capital city of Oyo State and is located about 145 km north-east of Lagos, Nigeria’s commercial capital city. The projected 2015 population of Ibadan using 2006 population estimates and assuming a 3% annual population growth rate was 3.3 million [21]. There are 11 LGAs in Ibadan. The 2013 Nigeria Demographic and Health Survey showed that only 25.8% of children aged 12–23 months in Oyo State were fully immunized with recommended routine vaccines [22].

In 2015, Nigeria was ranked as the 9th highest country in cellphone usage out of 217 countries globally with about 83 subscriptions per 100 citizens [23]. In the same year, Oyo State had about 7.5 million mobile phone subscriptions [24]. In Nigeria, an individual can have multiple telecommunication subscriber identity module (SIM) cards with different cellphones. These reports have shed light on the potential feasibility of cellphone-based reminder/recall interventions in Nigeria.

We conducted a cluster randomized controlled trial targeting children aged 0–3 months at recruitment paired with their mothers in a larger study which aimed at assessing the effects of a community health nurse-led intervention on childhood immunization completion in the study communities [25]. The larger study was conducted between August 2012 and February 2014 while the trial occurred between August 2012 and September 2013.

Four randomly selected LGAs out of the 11 LGAs in Ibadan were allocated into a cellphone reminder/recall intervention and a control receiving usual care. One ward was randomly selected from each LGA and one PHC center with a large population of children who come for immunization was purposively selected from each ward. Each study group therefore had two PHC centers. Health care providers working in the PHC centers were not aware of the group allocations. The enrolment of eligible children into the two study groups was done during their first immunization visit, which is usually their first contact with the health center. Overall, 305 children were enrolled into the intervention group and 309 children into the control group.

Ethical approval for the study was obtained from the Oyo State Research Ethical Review Committee. All mothers provided signed informed consent prior to participating in the study.

After the enrolment of each eligible child into the study at the first immunization visit, mothers in the intervention group (or their primary contact) received one cellphone call reminder from the nurse/researcher two days before the child’s next immunization appointment and a second call a day before the appointment date. Recall phone calls were made for missed appointments. If a child was not brought on the scheduled immunization day, the nurse/researcher automatically re-scheduled the child for the next immunization day. The pattern of recall cellphone calls was similar to that for the reminder phone calls. Follow-up of the children in the intervention and control groups lasted till the last scheduled immunization visit for each child. Phone calls were made between 9.00 am and 8.00 pm.

Data were collected using three questionnaires and one checklist. The first questionnaire was used to gather information on the socio-demographic characteristics of children and their parents, parents’ phone usage and mothers’ willingness to receive immunization reminder/recall phone calls. The second questionnaire recorded the children’s immunization data. The third questionnaire, which was adapted from an American Immunization Registry Association guidebook [26], documented reminder/recall activities for each child in the intervention group. The checklist was used for weekly tracking and follow-up of children due for immunization, and also for rescheduling missed immunization appointments.

Almost all, 590 (99.2%) of the mothers of the children had access to a cellphone with a valid number (either their own or belonging to someone else). These mothers provided one to five valid cellphone numbers where they could be reached. Ninety-eight percent (n = 584) of mothers agreed to receive immunization reminder/recall phone calls (Table 2).

Of the total 1162 cellphone calls made, 974 (83.8%) were reminder calls. Of the 974 reminder calls, only 41 (4.2%) were not received by the recipients. Similarly, only six (3.2%) of recall calls were not received. Eighty-five percent (n = 983) of all calls went through on the first day of each session of intervention. On the second day, a total of 1049 (90.3%) of all the 1162 sessions of calls went through (Table 3).

As shown in Table 4, mothers were the most frequent recipients of phone calls for the reminder/recall intervention. A maximum of five attempts were made if there was no answer or a busy signal. The mean duration for the calls was 29 s per session on the first day and 23 s per session on the second day of the intervention. The mean cost in US Dollars was about 5 cents per session on the first day and about 4 cents per session on the second day of the intervention.

The main trial outcome has previously been reported elsewhere [25]. Using DPT 3 coverage (which is a key indicator for assessing the effectiveness of childhood immunization services) [27], compliance rate was 79.2% for the intervention group and 46.4% for the control group (p < 0.001) (Fig. 2).

Study findings should be interpreted in light of several limitations. First, the study was based on a sample of children and their mothers recruited during the time of first immunization rather than a random community sample. The study therefore possible targeted those already predisposed to complete their vaccination. However, previous studies in Ibadan, Nigeria [40‐42] have found that many children who commence routine immunization do not complete the recommended vaccines. Second, the study was conducted in an urban setting and results may not be generalizable to rural and peri-urban settings. Third, only the costs of cellphone calls were captured in the study. Other costs, such as staff time and expenses for equipment and supplies were not captured. Thus, a comprehensive assessment of the cost of the intervention was not possible. Despite these limitations, this study demonstrates the acceptability, adaptability and effectiveness of a cellphone-based routine childhood immunization reminder/recall intervention in a low-resource setting in Nigeria.