The following databases were searched: PubMed, CINAHL, Nursing & Allied Health Database, Scopus, and PsycINFO. The following search terms were used: vaccine, vaccines, vaccination, immunization, vaccinated, vaccinate, vaccine hesitancy, parent, parents, mother, mothers, father, fathers, parental, social media, digital health information, facebook, twitter, pinterest, snapchat, tumblr, Instagram, linkedin, google plus, youtube, reddit, flickr, vine, quora, periscope, whatsapp, and internet. Search terms were combined using AND or OR in the database search. A research librarian was consulted to assist with the search strategy. A justification search was completed with the Allied and Alternative Medicine (AMED) database; this search revealed no further articles in the subject area. Grey literature was located by searching Proquest Dissertations & Theses Global. Reference lists of articles were hand searched to identify any further literature that met the inclusion criteria.

A title review of all articles was conducted for subject eligibility, followed by an abstract review and finally a full article review. A second reviewer read 15% of the articles to ensure consistency in data analysis to address the research question and purpose [22,23]. Discrepancies between inclusion of articles were discussed between the authors until consensus was reached. After eligible articles were identified, each was read several times for detail and to identify relevant categories and themes. Articles were identified by a numbering system and collated in a spreadsheet identifying country of origin, methodologies, limitations, instruments, methods, and key findings from an iterative and inductive analysis of all articles. Thematic analysis allowed for identification of relevant themes grounded in the data and gaps in the literature. An iterative analysis process was utilized by the authors; themes were identified through discussion and immersion in the literature. Discrepancies were reconciled through discussion until all themes were mutually agreed upon.

One of the most prevalent themes identified throughout the literature was one of information seeking; 50% (17/34) of articles discussed this theme [18,19,25-39]. Parents are looking online for vaccination information [18,26,27,30,31,39].

Online information seeking may have implications for the way that parents perceive the health and safety consequences of childhood vaccinations [20]. Canadian researchers investigated the impact of parental online information seeking through surveying parents and found that parents who searched the internet for childhood vaccine information (in 2011 and 2014) are more likely to perceive vaccines as less safe than those who did not search on the internet [20]. Yet, in another study also performed in 2011 that surveyed American parents, researchers found that 95% of parents of school-aged children who chose not to have their children vaccinated listed their health care provider as their main source of information, with only 34.5% reporting the internet as a source of information [25].

Mossey et al [34] evaluated Canadian parents’ experiences in making vaccination decisions. Parents identified that searching for information was an important part of their decision-making process and that locating and interpreting online information was difficult at times [34]. Reportedly, some parents looked for information online to confirm information provided by their health care provider; parents expressed concerns about their health care provider’s lack of knowledge regarding childhood vaccines [35]. There is some evidence that parents who delayed or declined vaccinating their children specifically sought information through online social media platforms, such as blogs and videos, appreciating the personal experiences from other parents found on theses platforms [34]. Jones et al [18] examined the information sources of parents of school-aged children in the United States who refused at least one vaccine for their child(ren). Researchers assessed the impact of diverse information sources on vaccine attitudes, beliefs, and medical exemptions. In this study, 40% of all respondents reported that the internet was a good source of vaccine information; however, only 19.9% of all parents in this study reported using the internet as a source of vaccine information [18]. Those who reported using the internet to obtain information about vaccines were less likely to agree that their children needed or would benefit from vaccines and were more likely to have obtained a nonmedical vaccine exemption for their child [18].

Hwang and Shah [33] examined the associations between health information sources, parental perceptions of vaccine benefits, and maintenance of vaccine schedules. They evaluated magazines, newspapers, television, the internet (search engines, general websites, drug company websites, and other health websites), interpersonal communication (doctors, nurses or physician assistants, pharmacists, and friends), and social media (social networking sites, blogs or vlogs) as health information sources [33]. Parents that valued social media as a source of health information reported fewer perceived benefits (identified as vaccine benefits outweighing vaccine risks) of vaccinations [33]. Positive parental perceptions of vaccine benefits were strongly associated with the maintenance of vaccination schedules [33].

Berreth [25] assessed sources of information among parents of school-aged children in the United States. They found that 95.4% of parents sought vaccine advice from their health care provider, 51.1% from family and friends, 34.5% from the internet, 25.3% from the news, and 15.5% from television and radio. Parents who cited the internet as a source of information listed the sites they most frequently used as webmd.com (34.4%), mayoclinic.com (27.5%), and government or other medically endorsed sites (68.9%) [25]. Researchers compared information sources of parents who vaccinated their child with those who exempted their children from vaccines. While 83.3% of immunizers versus 77.8% of vaccine abstainers identified health care providers as sources of vaccine information, only 25% of parents who immunized their children utilized the internet as a source of information compared to 44.4% of parents who did not immunize [25]. Deas et al [29] interviewed parents of school-aged children in 3 counties in the US state of Oregon with low immunization rates (combined pediatric immunization rate of 65%). Researchers found that all parents, regardless of vaccine acceptance or hesitancy, dismissed social media as they found it an unreliable source of vaccine information [29].

However, when exposed to evidence-informed online information, parental attitudes regarding childhood vaccinations shifted; researchers found that, after exposure to a vaccine information website developed by experts in the field, vaccine-hesitant parents had a more positive attitude toward vaccines compared to vaccine-hesitant parents with no exposure to the evidence-informed website [28]. Glanz et al [32] evaluated vaccine information-seeking behaviors in parents who accessed information from an online website. The website was developed and mediated by several experts (pediatrician, vaccine safety researcher, and risk communication specialist). Parents in this study preferred to engage with online experts about vaccinations rather than interacting with other parents within this online site [32].

Researchers who focused on the composition of search terms used by parents seeking online vaccine information found that parents who utilized positive search terms (eg, “vaccine benefits”) when looking for childhood vaccine information encountered few myths about vaccine safety and effectiveness [40]. In contrast, parents who used negative search terms (eg, “vaccine risks”) found 4.8 times more misinformation or myths than a person using positive terminology [40]. The nature of the search terms used to find online vaccination information can alter the results and the information made available to parents [40].

Parents searched online for vaccine information using common search engines such as Google and Yahoo, and many used popular social media sites such as Facebook, Instagram, Pinterest, Twitter, and YouTube [27,38,41-43]. One study found that the internet was listed within the top 3 most common sources for vaccine information among those who vaccinated their children, and 46% of parents who used the internet reported using search engines such as Google and Yahoo to search online for vaccine information [27].

The popularity of social media has given rise to prosumers — individuals who not only access online information but produce online content. Researchers found that websites that allow users to post online content without verification of information promoted antivaccination messages through antigovernment views, celebrities, personal stories, and naturalist arguments [43]. A Canadian assessment of online vaccine information websites (identified through searching Google, Facebook, Twitter, and YouTube) targeted to parents found that the majority of websites offered poor-quality information regarding childhood vaccination [42]. Researchers rated the websites with a communication index tool developed by the Centers for Disease Control and reported that 5% of materials (3 websites) met the standards for clear communication [42]. However, websites that monitored user-generated content and required academic references demonstrated a balance between openness and credibility [43].

Researchers assessed the content of online vaccine information, and there is evidence that content was conflicting and inconsistent [20,41,43-47].

Regarding online websites, American researchers investigating online information content generated from Google searching found that 59% of the first 100 Google sources were provaccine and 41% were antivaccine [43]. Similarly, Kata [46] sought antivaccination websites to assess their content and accuracy. Researchers utilized neutral vaccine information-seeking search terms (“vaccine,” “vaccination,” and “immunization OR immunisations”) to search American and Canadian versions of Google and found that, within the first 10 results, 24% of American and 13% of Canadian results were antivaccine [46]. A content analysis revealed that all of the assessed antivaccine websites claimed that vaccines are poisonous and cause idiopathic illnesses [46]. As well, 88% of the websites contained information that challenged the evidence about the efficacy of vaccines and whether vaccines conferred immunity, 88% endorsed alternative treatments (homeopathy, chiropractic care, naturopathy, or acupuncture) as superior to vaccination, 75% of the websites made accusations that regulatory bodies have information about vaccines that they are hiding from the public, and 75% of the websites suggested that vaccine promotion is solely motivated by profit seeking [46].

The content developers of websites advocating antivaccine messages used sophisticated strategies to communicate their perspective [48,49]. Researchers examined the content of antivaccine websites and found that these websites used persuasive tactics, attacked the credibility of vaccine advocates, expressed mistrust about scientific evidence, and used psuedoscientifc evidence to support claims in favor of antivaccination [49]. Similarly, Getman et al [48] performed a network analysis of over 50,000 websites that contained vaccine-relevant content to determine the structure and influence of the online vaccine-hesitant community. They discovered effective use of hierarchical scientific language by the vaccine-hesitant community to enforce their online authority [48].

Regarding social media vaccine resources, researchers evaluated literature on vaccine information on the following social media platforms: YouTube, Twitter, Pinterest, Facebook, and various blogs. Facebook was identified as a vaccine information resource for parents in several studies [20,38,42,50]. The majority of research literature that focused on social media use among parents was published between 2015 and 2019, reflecting parents’ recent use of social media for seeking vaccine information. Parents also accessed social media sites to understand other parents’ experiences with vaccination processes; peer-to-peer information was a valued source of information accessible on social media sites [50]. Across social media platforms, there was a mix of positive and negative vaccine messaging. Our findings indicate widespread mistrust of government institutions and skepticism towards the vaccine industry across all social media platforms except for pediatrician-authored blogs [37,41,44,45,47,50-53]. Vaccine-hesitant online communities tend to leverage scientific and academic language to enforce their antivaccination narrative [48]. Consistent messaging about the dangers of vaccines was present on Twitter, Facebook, YouTube, parenting blogs, and Pinterest. The dominant message across social media was one of elevated health risks among vaccinated children — perceived as information concealed by government and industry.

The concept of trusted health care providers was prevalent in many of the reviewed studies [18,20,27,30,31,34,35,45, 46,49,50]. Parents often listed their physician or health care provider as a trusted source of vaccination information [18,27,30,31]. Eller et al [30] examined the association between the level of trust a mother had with their pediatrician and vaccine information sources. Mothers who trusted their pediatrician were 2.47 times more likely to list their pediatrician as their main source of vaccine information compared to mothers who had not established a trusting relationship with their pediatrician [30]. Parents who chose to vaccinate their children reported their physician as the biggest influence in their decision to vaccinate [27].

However, parents who identified as vaccine-hesitant or those who did not vaccinate their children were less trusting of information conveyed by their health care provider [27]. Parents who chose to delay or declined vaccinating their children tended to seek information from a diverse group of health disciplines such as cardiologists, health researchers, health care students, and homeopathic practitioners [34]. Kata [46] identified mistrust in the medical system as a strong message on antivaccine websites and on an antivaccination Facebook group [46,50].

This review evaluated parental information seeking in those who have internet access; it did not capture parents who have limited or no access to online health information. The online environment is fluid due to its interactive user-driven features with websites and social media evolving and changing from day to day. Findings involving online information should be viewed cautiously as digital information changes rapidly. This review included English-only research reports, and research literature in languages other than English may have findings that are different than reported here.

This review identified that parents are looking online on major search engines and social media platforms for vaccine information. It was identified that locating accurate information online regarding the benefits and risks of vaccines is challenging for parents given the low number of sources that contain accurate information [42]. There was conflicting evidence about how parents utilize information found online to inform their vaccine choices. However, vaccine-hesitant parents who have access to accurate online vaccine information have significant improvement in attitudes regarding vaccination benefits and reduction in parental concerns about vaccination risks [28]. Given the plethora of misinformation perpetuated online, clinicians may want to provide “information prescriptions” to parents regarding the search terms they use and encourage parents to access websites moderated by health care experts. The interactive component to the websites would provide an opportunity for parents to ask questions of vaccination experts. Health care providers should discuss with parents the nature of online vaccine discussions. Reviewing with parents the utilization of hierarchical and scientific language utilized by some to promote antivaccine messaging. Further discussion focused on search terms and even providing parents suggestions for vaccine-positive or neutral terminology that will allow them access to a more balanced discussion of vaccine benefits and risks online.

Parents identify trust as a fundamental part of the vaccine decision-making process. This importance placed upon perceived trust in the source of information reinforces the importance of relational care practices, and a trusting relationship with a health care provider is a priority. Developing and fostering trust between primary care providers and parents may be a strategy to increase vaccine uptake by parents.