Outbreaks of vaccine-preventable diseases, such as the measles, mumps, rubella, and diphtheria, have risen over the past decade [1-3]. While mortality rates of vaccine-preventable diseases are relatively low, certain groups, including children under 5 years of age and people with a compromised immune system, are at greater risk of severe complications [2]. The decline in the uptake of routine childhood vaccinations has been identified as a cause for outbreaks of vaccine-preventable diseases. Immunization coverage has declined for nine routine childhood vaccinations measured at different child ages in England; vaccination rates fell by 0.2%-1% in 2018-2019 compared to the previous year [4].

There are numerous interrelated reasons for the decline in childhood vaccinations, including concerns about side effects, fear of autism, objection against many injections, moral or religious grounds, costs, access, and other reasons [3]. A commonly mentioned reason is misinformation and false evidence, for example, claims by the discredited ex-physician Andrew Wakefield who linked the measles, mumps, and rubella (MMR) vaccine to autism in 1998 [5]. Religious and philosophical reasons have been used by certain groups to decline vaccination of their children [6]. Particular communities have been consistently difficult to engage, for example, male-dominated societies often resist vaccination against human papillomavirus (HPV) [7,8]. The seriousness and relative rarity of these illnesses has reduced some people’s awareness of the importance of vaccination. Visiting a health clinic for vaccinations might be an inconvenience or may also be forgotten about [3], particularly as reminders to attend a clinic for vaccinations are not part of routine health care in all countries.

There have been several initiatives to improve the uptake of childhood vaccinations in different settings [9,10]. These include a range of informational, behavioral, and environmental initiatives. Health care provider initiatives have focused on patient counseling, maximizing the opportunities of each visit, combination vaccines, and automated electronic patient record reminders. Community-based approaches to increase vaccination rates include increasing outreach and educational programs, using recall and reminder strategies, providing financial incentives, and offering vaccinations at nontraditional sites [3].

Over the past decade, public and private organizations have developed tools to improve vaccination coverage, including vaccination information websites and apps [11]. These apps help health care providers and patients to access reminders for recommended immunization schedules and related vaccine resources and websites; they also allow for changes in the schedules through app updates.

Vaccination apps can be used as a tool to provide reminders, information, peer support, and feedback [12]. A cluster randomized controlled trial showed that an app used by village doctors, which included text messages to caregivers, improved full vaccination coverage in China. Village doctors using the app reported improved efficiency in managing childhood vaccinations [13]. A quasi-experimental pre-post study using an app to electronically register child births and sending text message reminders to parents about upcoming vaccinations showed improved vaccination coverage in rural hard-to-reach and urban street dweller communities in Bangladesh [14].

A systematic review that assessed interventions to improve immunization coverage in England concluded that current practice is insufficient [15]. Vaccination apps might be used to help improve immunization coverage but, to our knowledge, no recent systematic reviews have assessed the evidence on childhood vaccination apps. A systematic review on the design of a vaccination reminder app identified two publications on mobile apps, but the search was limited and conducted in 2015 [12]. Furthermore, this review did not assess all important quality indicators, including whether the app was secure, usable, engaging, efficacious, and cost-effective [16].

Our objective is to systematically review the evidence on childhood vaccination apps by assessing the following:

This is the protocol for a systematic review of the literature that will be reported, where possible, according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses for Protocols (PRISMA-P), as provided in Multimedia Appendix 1 [17]. Our review will follow, where possible, the Cochrane Collaboration [18] and the Centre for Review and Dissemination [19] methodologies for conducting systematic reviews.

Relevant articles will be identified by searching the following electronic databases: (1) PubMed, (2), Embase through Ovid, (3) Web of Science, (4) Cochrane Central Register of Controlled Trials (CENTRAL) [22], (5) ClinicalTrials.gov, and (6) Education Resources Information Center (ERIC).

A draft search strategy can be found in Multimedia Appendix 1. This will be tailored to the different databases, with the assistance of a medical research librarian. No study design filter will be used, as both quantitative and qualitative studies are to be included. We will use the titles, abstracts, and keywords of a set of articles that we know meet our inclusion criteria to define a search strategy that will return all these articles without an unmanageably large number of irrelevant articles.