Honey&Banana (H&B) is a program dedicated to provide family planning information and services, which involves pregnancy prevention, child spacing and family size limitation. It is implemented by DKT International Nigeria (DKT). To receive confidential family planning advice, individuals are encouraged to use the program’s website, social media pages, or its toll-free call center. H&B focuses primarily on modern, long-acting reversible contraceptive methods (LARC). The call center can be reached by calling 55059; all call center agents have been trained to provide confidential information about family planning and ways to access it. If a caller intends to use a family planning method, the agent will refer them to a local family planning clinic from DKT’s network of partner clinics. The call center offers family planning information in five different languages: English, Hausa, Igbo, Yoruba, and Pidgin English.

To promote the call center, H&B developed a large-scale radio jingle campaign that aimed to increase the number of callers requesting family planning information. Because 19% of currently married women and 48% of unmarried sexually active women have an unmet need for family planning ( National Population Commission (NPC) and ICF International, 2019), the latent demand for family planning information is believed to be high. The campaign was diffused on 28 radio stations throughout 12 states (Abia, Abuja FCT, Delta, Edo, Kano, Lagos, Nasarawa, Niger, Ogun, Oyo, Rivers, Sokoto). These states were chosen because of the presence of numerous partner clinics that would be able to handle the anticipated increase in demand for family planning services. The campaign was done by using seven different jingles that encouraged individuals to contact the call center for family planning information or to request a referral to a family planning provider. As such, the jingles aimed to address the latent demand for family planning information (rather than to provide family planning information or education). Given the size of the campaign, a large increase in the volume of calls was anticipated. It was also hoped that awareness of the call center would subsequently spread further through word of mouth.

The radio jingles were broadcast in English, Pidgin, or Hausa, depending on the location, starting in December 2021. The original plan was for the campaign to run for six months, starting in December 2021. However, based on monthly feedback on the number of requests for family planning information received by the call center, the implementers decided to end the campaign in March 2022.

This paper applies a single group interrupted time series design as a responsive feedback mechanism for assessing whether the Honey&Banana radio campaign helped increase use of the call center. Interrupted time series studies have been used to measure the effect of a wide range of public health policies and programs ( Booth et al., 2018; Cheng et al., 2016; Fuseini et al., 2022; Hategeka et al., 2020; Hudson et al., 2019; Humphreys et al., 2017; Ma et al., 2020; Owuor & Amolo 2019; Ramsay et al., 2003; Turner et al., 2020). However, they are typically used as an end-of-intervention impact evaluation ( Bernal et al., 2019), rather than a responsive feedback mechanism.

The most basic form of the ITS design simply examines the overall trend in a key outcome measure. This design is typically used when no control group is available. When the outcome measure is graphed over time, an interruption of the trend is expected to occur after the start of the intervention. This interruption may entail a change in the level of the outcome measure, a change in the rate at which the outcome had been improving, or both ( Bernal et al., 2017). The ITS design then uses the pre-intervention trend in the desired health outcome to predict what likely would have happened in absence of the intervention. In other words, the counterfactual is based on the assumption that the pre-intervention trend would have continued. Comparison of the actual and projected trends gives an estimate of the impact of the intervention. Because this can be done for successive time intervals ( e.g. every month or quarter), implementers get continuous feedback about the effectiveness of their intervention.

To use interrupted time series analyses of routine monitoring data as a responsive feedback mechanism, the intervention activity needs to have a clearly defined starting point. Many family planning programs implement social or mass media campaigns ( e.g. to encourage contraceptive use) that fit this requirement. Because several pre- and post-intervention data points are needed for the analysis, routine monitoring data ( e.g., the monthly number of family planning clients or the number of contraceptives distributed) that are collected at fixed intervals are an ideal data source.

Our study uses monitoring data on the monthly number of calls received during the pre-campaign period (January to November 2021) to calculate 1) the linear trend in the number of calls, and 2) the logarithmic trend. For simplicity, we estimated the pre-intervention trend with the “trend line” option in Microsoft Excel 365. Although more advanced modeling programs are available, Excel has been used in other studies (see Turner et al. (2020)) and has the advantage that the approach can easily be replicated by programs that have limited internal research capacity.

The linear trend assumes there is a steady increase in the number of calls received. The logarithmic trend assumes that the number of calls initially increases fairly rapidly, but then levels off. It has been noted that it is important to consider whether a linear model is appropriate, as certain outcomes may hit a natural ceiling ( Jandoc et al., 2015). Since other sources of family planning information exist, the number of people who are interested in using the call center may eventually hit a ceiling. Hence, in the long term the logarithmic trend may be more realistic. We opted to model both the linear and logarithmic trends and used the relevant equations to project the expected number of calls in absence of the radio campaign. The formulas for the linear and logarithmic equations were used to calculate the projected number of calls for the months from December 2021 through May 2022.

Time series data can be affected by autocorrelation, for example when data points that are close together tend to be more similar than those further apart. Autocorrelation in the pre-intervention data could affect the estimation of the trends that are used to generate the post-intervention counterfactual. Although we have no theoretical reason to suspect the presence of autocorrelation in the pre-intervention data, we heeded the recommendation to test for autocorrelation ( Raadt, 2018). We used R Project software (version 4.2.2) to conduct the Durbin-Watson autocorrelation test. The values of the Durbin-Watson test range from 0 to 4, a value of 2.0 indicating that no autocorrelation is detected. The results of the test confirmed that there is little or no autocorrelation in our pre-intervention data (DW=1.9421; p=0.3112).

For our study, we anticipated that there would not be any substantial lag between the start of the radio jingles and the desired increase in the number of incoming calls requesting family planning information ( Bernal et al., 2017). A lag is unlikely to occur because the radio campaign provides potential callers with an immediate solution for their unmet need for family planning information and because they are most likely to contact the call center while the call center short code is fresh in their memory. Hence, we anticipate observing an increase in the number of calls received, as soon as the campaign started in December 2021. For each of the estimation models (linear and logarithmic ITS), we estimated the effect of the radio campaign by calculating the difference between the actual and projected number of calls received for the period from December 2021 through May 2022.

As the exposure to the radio campaign was not randomized, it is important to acknowledge that other factors, such as different program activities, may have influenced the use of the call center. These variables could possibly lead us to misinterpret how well the radio campaign was working. Since projected trend assumes the pre-intervention trend will continue, it is important to ensure that the pre-intervention trend – including any outliers – is well understood. Prior to the intervention, H&B carried out two brief campaigns which could have increased use of the call center. Between April 1 to May 30, 2021, H&B launched a campaign to encourage use of Sayana Press injectable contraceptives, reaching out to existing users to remind them of their next injection date, and sending an SMS blast to previous users who had not received an injection for over three months. In August 2021, H&B conducted several promotional activities in celebration of the third anniversary of the call center, including intensified activities in affiliated family planning clinics, digital and social media platforms, and a small e-voucher campaign. From February 14 through March 31, 2022, DKT also conducted an HIV self-testing campaign during which self-test kits were distributed to post-secondary students in 29 states. Although this campaign did not focus on family planning, students were advised to contact the Honey&Banana Connect call center with any questions or concerns, which may have increased the volume of calls during the radio jingle campaign.

Through the H&B website, DKT's contraceptive products, H&B's social media pages, and the radio campaign, the call center toll-free number is being widely promoted. However, the H&B website was offline from January to November 2021 due to a major attack and was subsequently redesigned. While the restored website was launched at the same time as the radio campaign, it mainly focuses on providing information about contraceptive products. The homepage displays the call center logo and phone number but primarily provides details about the different contraceptive products available, with links to request information about nearby certified family planning clinics and an online store. The toll-free number is also printed on the packaging of most DKT contraceptive brands, such as Fiesta condoms. Regular daily social media posts on Facebook and Instagram also list the toll-free number throughout the study period. As none of these channels were specifically focused on the period from December 2021 to March 2022, it is unlikely that they significantly influenced the results.

There are other potential factors that may have affected the results, such as family planning programs implemented by the Nigerian public sector and other non-governmental organizations. The Society for Family Health and PSI Nigeria are two examples of non-governmental social marketing organizations that work across the country and deliver access to subsidized family planning products and promote their use. The Nigerian Urban Reproductive Health Initiative, implemented by Johns Hopkins Center for Communication Programs, also aims to increase contraceptive use in specific states including Lagos, Kaduna and Oyo. These programs may have affected the increase in demand for family planning information and services, but we are not aware of any programs that were implemented during the diffusion of the radio campaign (December 2021–March 2022). These organizations' communication activities aim to address the demand for family planning information, so they are unlikely to confound our analysis.

The data source for this responsive feedback study consists of public records on the number of incoming calls received by the Honey & Banana Connect call center, as published by DKT International Nigeria ( Olutola et al., 2023). The database excludes calls that were not related to family planning ( e.g., wrong number, crank calls, or calls not related to family planning). DKT generated the database based on customer records about all incoming calls received by the call center, which are entered using Customer Relations Management (CRM) software. The number of family planning related calls was extracted from the CRM customer records and aggregated by calendar month for inclusion in the database. Our outcome indicator is the monthly number of incoming calls that were related to family planning. Our study analyzes call center records of the 12,490 incoming calls received by the call center during the period from January 1, 2021 through May 31, 2022. Although using a longer post-intervention period is preferable when there are no known confounding factors (such as other campaigns), this was not feasible due to the start of an H&B e-voucher campaign in June 2022.

The Tulane University Human Research Projection Office determined that this study is not human subjects research as define by the Common Federal Rule and does not require IRB review and approval (Ref #2023-590).

One of the main limitations of our study, which it shares with all ITS studies, is that it relies on an artificially constructed counterfactual that may not accurately represent what truly would have happened in absence of the intervention. Therefore, the accuracy of the estimated magnitude of the intervention impact depends heavily on the assumption that the pre-intervention trends would have continued. Outliers in the pre-intervention trends, like the ones that were observed in our example, can affect the accuracy of the projected trend. The two outliers in our example resulted from small interventions conducted by H&B itself and that are typical H&B activities. Hence, it is reasonable to assume that the pre-intervention trend would continue. Nevertheless, use of a single group ITS design with routine monitoring data can be a valuable approach to receive responsive feedback about a new intervention is working, even if the exact magnitude of the intervention effect is uncertain.

Another limitation of the ITS design is it cannot easily be used when there are other competing campaigns. Due to the launch of a large-scale e-voucher campaign, we only have two data points after the radio campaign ended, which limited our ability to assess any longer-term effects of the campaign.

A number of authors recommend visually inspecting pre-intervention trends for instability and potential outliers prior to ITS analysis ( Biglan et al., 2000; Jandoc et al., 2015). High variability in the pre-intervention time series makes it harder to detect an intervention effect. Outliers may indicate that the ITS assumption that the pre-intervention trend would have continued in absence of the intervention is not valid. Some authors therefore re-analyze the data with the outliers removed ( Hudson et al., 2019).

Figure 1 shows the observed trend in the number of calls requesting family planning information received by the call center, with the intervention period shaded in green. During the pre-campaign period (from January through November 2021) the monthly number of calls hovered roughly between 400 and 550, except for two notable outliers. The first outlier is the peak in April–May (827 and 721 calls, respectively), which coincides with the period when the program conducted a campaign to promote the use of Sayana Press injectable contraceptives ( Honey&BananaConnect, 2022). The second outlier is the peak of 842 calls in August, which coincides with the third anniversary of the call center. As part of the anniversary celebrations, the program intensified social media promotions of the call center, and implemented a small e-voucher campaign for free contraceptives ( DKT International Nigeria, 2021). The anniversary also was also noted in the press, which may have further increased awareness of the call center ( Brand Spur Media and Marketing Services, 2021; News Wings, 2021). Apart from these two temporary peaks, the monthly number of requests for family planning information showed fairly little variation during the pre-campaign period, and increased only minimally.

Following the start of the radio campaign in December, the number of calls requesting family planning information nearly doubled, from 554 in November to 1,064 in December. It stayed at roughly this level through February (995 calls), and further increased to 1,471 in March. This latter increase may have resulted from the HIV self-testing campaign that was conducted at post-secondary institutions. Recipients of the self-test kits were advised to contact the Honey&Banana Connect call center with questions or concerns, which may have increased the volume of calls. By April, when the radio campaign had ended, the number of requests for family planning information decreased, but remained substantially above the pre-campaign levels (852 calls in April; 961 in May).

Although the trend shown in Figure 1 clearly indicates that the radio campaign had an effect on use of the call center, it would be helpful to have an estimate of how big that effect was in terms of the net number of callers gained. To measure the impact of the radio campaign, we need to estimate how many requests for family planning information the call center would have received in absence of the campaign. Single group ITS assumes that without the campaign, the pre-intervention trend would have continued. We estimated both the linear trend (which assumes a steady increase) and the logarithmic trend (which assumes a rapid increase, followed by a leveling off).

Based on the pre-intervention observed data, the linear trend was estimated as y = 2.8273 x + 544.13 and the logarithmic trend as y = 46.002 ln⁡( x) + 487.9, where y is the number of family planning related calls and x the time period (in months). Due to the random fluctuation and the two outliers, neither trend explained the variability in the number of calls. ¹ After the start of the radio campaign, the level of the trend was notably higher, while the gradient was slightly negative (linear trend: y = –11.657 x + 1093.8; logarithmic trend: y = –12.14 ln⁡( x) + 1066.3).

Figure 2 shows the actual trend in the number of calls received during the entire study period, as well as the projected trend in absence of the radio campaign for the period from December 2021 through May 2022. The green line assumes that the trend is linear; the light blue line assumes that the trend is logarithmic. Consistent with our earlier observation that the monthly number of calls during the pre-campaign period was nearly constant (with the exception of the two peaks), both projections suggest that there would only have been a minimal increase in the number of requests for family planning information. Based on the linear projection, it is estimated that in absence of the radio campaign the monthly number of calls would have gradually increased from 554 in November (actual) to 592 in May. Based on the logarithmic projection, the increase would have been from 554 to 618.

Visual comparison of the projected and actual number of requests suggests that the radio campaign generated 400–800 additional information requests per month, for the duration of the campaign (December through March). Moreover, the data for April and May suggest that once the campaign had ended, the number of information requests remained considerably above the pre-campaign levels.

The difference between the actual number of calls received and the projected numbers is our estimate of the effect of the radio campaign on the number of callers requesting family planning information. Table 1 shows the actual number of calls received, the predicted number of calls using our two types of counterfactuals (ITS with linear and logarithmic projections), and the estimated number of calls gained for each model.

For the period from December 2021 through May 2022, the linear projection model estimates that there were 2,807 additional calls requesting family planning information, while the logarithmic projection puts the gain at 2,654 calls. While the true effect size of the radio campaign remains unknown, our analyses suggest it is likely be in the range of 2,600–2,800 additional requests for family planning information. To put that estimate in context, it implies that the radio campaign added the equivalent of the total number of requests for family planning information the call center would normally receive over a four to five month period. However, most of the gains occurred during the months while the radio campaign was active. As soon as the campaign ended, the gain in calls dropped to only 250–350 calls per month. In other words, the feedback data indicate that the radio campaign only led to a temporary increase in demand for family planning information.