Thank you for your thoughtful and detailed review. We've tried to address each concern separately below (reviewer comments in italics, responses in normal text):

This study highlights the need for reproductive, maternal, newborn and child health (RMNCH) interventions in Afghanistan. There is a need for RMNCH interventions to be targeted towards youth, aged 15 to 25 years old, which make up more than half of the Afghani population. Internally displaced persons (IDPs) within this population have even greater barriers to access maternal and child health care. Due to IDPs being a unique population and harder to reach, mobile technology could be used to bridge the access gap in health care. The study aimed to measure the current and preferred RMNCH information channels with an emphasis on exploring the feasibility of using mobile phone technology to reach the IDP youth population.

The results of this study are important to the field especially as it covers a hard to reach population. Other strengths of the study are its large sample size over three provinces, with almost equal male and female participants within each province. Additionally, the methods show great cultural competency, which is crucial when conducting a research study within a community.  

Current recommendations to the authors are listed below:

Brief mention of where the survey data comes from is needed and the purpose of the overall project should be added. Looking at the references within this section, the data seems to come from the United States Agency for International Development (USAID)-funded Helping Mothers and Children Thrive in Afghanistan (HEMAYAT) project. Further explanation of this project would strengthen the paper and deepen understanding. 

“We conducted a sub-group analysis of survey data collected in a mixed-methods, cross-sectional, formative assessment to inform programming for the United States Agency for International Development-funded Helping Mothers and Children Thrive in Afghanistan project. ²¹ The assessment was designed to gather information from youth 15-25 years and adult men > 25 years of age to identify health information and service gaps related to RMNCH outcomes and inform content and channel selection to segments of these populations, including IDPs, for targeted programming. For these analyses, we include data from a convenience sample of female and male IDP youth, ages 15 to 25 years. Youth who self-identified as IDP were recruited from households located in areas with large IDP populations in Kandahar, Nangarhar, and Takhar Provinces, selected based on their geographic and ethnic diversity. Survey data were collected March-July 2017 using a structured questionnaire administered through face-to-face interviews conducted by trained research assistants. Data used for these analyses include participant background information, household possession of media devices (i.e. television, radio and mobile phones), exposure to health information from various channels, desires for various types of health information and preferred channels of communication, as well as likelihood to use a free mobile phone-based system to receive health information.” 

Formative research is primarily used for developing intervention strategies, materials and instruments. Commonly formative research approaches are developed using a theoretical framework. Methods should be expanded to include how this formative approach was developed. 

“We conducted a sub-group analysis of survey data collected in a mixed-methods, cross-sectional, formative assessment to inform programming for the United States Agency for International Development-funded Helping Mothers and Children Thrive in Afghanistan project. The assessment was designed to gather information from youth 15-25 years and adult men > 25 years of age to identify health information and service gaps related to RMNCH outcomes and inform content and channel selection to segments of these populations, including IDPs, for targeted programming.”

The random walk technique used for sampling should be explained in further detail, including why this method was chosen over other methods. How does this method reduce bias? 

“Households in these communities were sampled using a random walk technique.  ²² The approach used for this random-walk sample involved selecting a central community landmark, such as a mosque, then selecting one house at random to be the starting point. From there households were approached at regular intervals (e.g. every 3rd) Household selection continued in each area until reaching the requisite sample size.”

< > In the methods the authors state that they were specifically targeting youth and adult men, but when looking in the recruitment section it appears, they are targeting men and women equally.Looking at the demographics of the study it looks as if there are significant differences in men in the Takhar province than the other two. While women were similar in demographics across the three provinces, men in the Takhar province had lower levels of educational attainment and low levels of literacy. This difference should be noted within the paper. Noting these differences not only with demographics but in the other sections of the analysis is important as certain provinces may have different wants/needs. If these populations are significantly different from each other then they may also have different needs within an intervention. The authors conclude that an RMNCH intervention is “potentially feasible” and “likely accessible to more IDP youth” than other forms of communication. The results appear to show low feasibility for this type of intervention, due to low literacy rates, smart phones being owned and controlled predominantly by males, and overall preferred sources of RMNCH coming directly from health care providers. Although many IDP youth own mobile phones there would be many barriers to overcome to implement a successful mobile intervention. A majority of participants reported being “likely to use a free mobile phone-based intervention,” this high rate of “intention to use” does not always translate into a behavior change. Actual feasibility conclusions should be drawn from a pilot study using an RMNCH intervention.

We appreciate the reviewer’s comments; however, as noted in the discussion, if the intervention used voice messaging (either through live persons or voice recordings) then the literacy challenge would be addressed. Smartphones would not be needed for either a voice- or a text-based intervention, and we hope we have not given the impression that they would be required.

We agree that face-to-face client-provider interactions are ideal based on the preferred source of health information for most participants; however, access to such interactions is limited, for multiple reasons, which is why alternative, complementary strategies are required.

In terms of self-reported likelihood to use a hypothetical intervention, we absolutely agree. We’ve revised the text in the last paragraph to more explicitly support the need for documenting the actual feasibility of the approach on p. 9:

“Although findings from this study are exploratory, we believe that mobile phone-based programming, if appropriately marketed, presents a promising channel to reach IDP youth. Further research is needed to more thoroughly document feasibility, as well as to understand the most cost-effective mobile phone platforms to use. It will also be important to refine content for various RMNCH topics and channel selection to target specific segments of these sub-populations. We recommend that mobile phone-based RMNCH programming be developed and tested specifically for youth, with purposive inclusion of IDP populations in multiple settings to ensure cultural congruence and acceptability. The resulting interventions should be rigorously tested for cost-effectiveness to help guide national policy for youth programming amidst budgetary limitations and increasing insecurity.”

We thank the reviewer for his constructive feedback on this manuscript and submit the revised version along with responses to critiques.

Reviewer input is in italicized font and we provide our response and the relevant changes after each critique.

This cross-sectional survey reports on a topic and youth group that has had very little attention in the literature. Certainly, I’ve seen no similar report and as the authors rightly conclude, displaced youth in places like Afghanistan have been little studied. This population also poses quite a few challenges in surveys of this kind, as the authors again point out. The paper is generally well-written and the tables/figure are straightforward and clear. Inevitably there are methodological limitations, many of which the authors to flag. Some remained significant.

1) The sampling methods are not clear enough. Given the relatively small numbers, I am assuming this is not aspiring to be a representative sample of the target population. However, it isn’t clear how these participants were selected. No details are given of response rates, including characteristics of non-responders. These details are important.

This is not a representative sample, as noted in the limitations of the original manuscript. We have provided additional details on sampling strategy on pp. 2-3 (italicized text below):

“We conducted a sub-group analysis of survey data collected in a mixed-methods, cross-sectional, formative assessment to inform programming for the United States Agency for International Development-funded Helping Mothers and Children Thrive in Afghanistan project. ²¹ The assessment was designed to gather information from youth 15-25 years and adult men > 25 years of age to identify health information and service gaps related to RMNCH outcomes and inform content and channel selection to segments of these populations, including IDPs, for targeted programming. For these analyses, we include data from a convenience sample of female and male IDP youth, ages 15 to 25 years. Youth who self-identified as IDP were recruited from households located in areas with large IDP populations in Kandahar, Nangarhar, and Takhar Provinces, selected based on their geographic and ethnic diversity. Survey data were collected March-July 2017 using a structured questionnaire administered through face-to-face interviews conducted by trained research assistants. Data used for these analyses include participant background information, household possession of media devices (i.e. television, radio and mobile phones), exposure to health information from various channels, desires for various types of health information and preferred channels of communication, as well as likelihood to use a free mobile phone-based system to receive health information.

Geographic areas were selected based on guidance from UNHCR, the Ministry of Refugees and Repatriation, and the Danish and the Norwegian Refugee Committees, who have pre-existing relationships with IDP communities and their leaders. Households in these communities were sampled using a random walk technique. ²² Household selection continued in each area until reaching the requisite sample size. Verbal informed consent was obtained from eligible youth interested in participating then a structured questionnaire was administered by sex-matched data collectors in a private setting within the house.”

and response rates on p. 4:

“A total of 462 IDP youth were recruited to participate in the survey. Ten of the 462 declined participation (2.2%); one person consented, but refused to answer the remaining survey questions and data from one further participant was dropped because of incomplete interview, leaving 450 total study participants in Kandahar, Nangarhar, and Takhar Provinces including 225 male and 225 female youth. Characteristics of non-responders are not available as once a person declined to participate, no further information was recorded.”

2) One problem in interpreting the findings is the definition of internally displaced. The authors do mention this in the discussion as a limitation, but it seems that these groups are actually young people living in areas where there are high levels of internal displacement? I was clear if they were displaced themselves – if not perhaps the title of the paper should be changed?

Although we did not collect additional information on displacement characteristics, eligibility was constrained to youth who self-identified as IDPs. Data collectors asked the youth if they were internally displaced before proceeding to the informed consent process. This information has been added to the manuscript on p. 3:

“For these analyses, we include data from a convenience sample of female and male IDP youth, ages 15 to 25 years. Youth who self-identified as IDP were recruited from households located in areas with large IDP populations in Kandahar, Nangarhar, and Takhar Provinces, selected based on their geographic and ethnic diversity.”

3) It would be very good if the authors could elaborate on reasons for internal displacement of youth in Afghanistan. I’m assuming that conflict and unrest is one factor but there are a range of others that are very significant: marriage in girls; employment in boys; and there may be a range of other reasons as well e.g. access to education. This is important for the reader to understand.

As noted by UNESCO, “Guiding Principles on Internal Displacement set by of Office for the United Nations High Commissioner for Refugees (UNHCR) holds internally displaced persons to be "persons or groups of persons who have been forced to flee, or leave, their homes or places of habitual residence as a result of armed conflict, internal strife, and habitual violations of human rights, as well as natural or man-made disasters involving one or more of these elements, and who have not crossed an internationally recognised state border." ( http://www.unesco.org/new/en/social-and-human-sciences/themes/international-migration/glossary/ displaced-person-displacement/). However, it could certainly be argued that the line between forced and unforced migration can be blurry. 

We noted in the discussion section, a limitation of the study is that we did not collect information from participants on reasons for displacement. We do, however, report in the second paragraph of the background section, main drivers for internal displacement (forced migration) in Afghanistan, which include conflict, natural disasters and poverty, as documented through other research; youth move with their families as the family unit tends to stay intact in situations resulting in displacement. We did not explore reasons for voluntary migration in detail.  

Please see the text on p. 1:

“Years of armed conflict, natural disasters like drought and flooding, and widespread poverty have led to large-scale migration of intact family units both within and from Afghanistan. ^9-11”

4) The conclusion that the authors draw is that there would be scope for communicating with males, and to a lesser extent, females through mobile phones to provide health information. Given youth preferences, this would ideally be a system with a real person at the other end of the phone line. Could the authors provide some examples of where this has been rolled out, ideally with information on coverage and costings, with some discussion as to whether this might be affordable and scalable in the context of Afghanistan?

To date, there is no published evidence on the use of mobile phones for health promotion interventions in Afghanistan. Based on a search of the current literature, only one study has been published on the topic from Afghanistan - a descriptive study exploring women’s perceptions around using mobile phones to promote maternal and child health. There is very little in the published literature on the effectiveness of health promotion programs that employ voice messaging or live interactive phone calls in LMIC, and even less on costs. Many programs are currently being implemented, but the evidence lags behind. A number of protocols examining similar interventions have been published, but studies have not yet been completed. Of note, the HEMAYAT project, which led this formative research, is currently piloting a voice messaging intervention to promote RMNCH among pregnant and postpartum women. However, as with many of these interventions, the work is still underway. These limitations in the current literature are noted on p. 8:

“There is limited reported evidence on the use of messaging strategies for mobile phones other than SMS, and to date, there is no published evidence on the use of mobile phones in health promotion interventions in Afghanistan. ¹⁴ Authors of a 2017 systematic literature review on mHealth strategies in low- and middle-income countries found that most intervention strategies used SMS-based messaging, though a few incorporated social media apps, such as Facebook, and one program in Papua New Guinea employed the use of voice messages and an interactive information hotline to promote youth-friendly sexual and reproductive health information for young people ages 15 to 24. ¹⁴ Although studies and project reports have documented successful implementation of mobile health strategies, SMS messaging predominately, a 2019 review notes a number of important barriers, including telecommunications infrastructures, costs, literacy and language barriers, among others, that will require careful consideration, planning and assessment as future interventions are developed and evaluated. ³⁰”

5) The researchers seemed quite dismissive of mass media strategies for providing information to youth. Yet there are some very good examples of using mass media and low- and middle-income countries to provide information on sexual and reproductive health. It would be good if the authors could go back and re-examine this literature as mass media do provide an alternative platform for delivery of information at scale – the costs of doing so are likely to be quite a lot lower than individualised manning of telephone lines.

Our aim was not to be dismissive of mass media, but rather it was to place our findings in the context of what is known about reaching youth with health information in this particular setting. There are indeed examples of mass media to influence health-related knowledge and attitudes, and to a lesser extent, health-related behaviors in other countries. We have revised our summary on p. 8 to read

“Mass media campaigns are another health information strategy with some evidence for increasing health-related knowledge and attitudes, and to a lesser extent, health-related behaviors. service use, though the evidence is weak, and effectiveness for changing health behaviors is not well documented.”

However, our findings indicate that access to traditional mass media channels (e.g. radio and television) is limited among our study participants and varies considerably across provinces. In Takhar, for example, fewer than one in four of men and women had access to either radio or television, thus limiting their potential effectiveness, hence the need to identify other communication channels.