Microneedles (MNs) are designed to specifically target the outermost, skin barrier layer, the stratum corneum, creating transient pathways for minimally invasive transcutaneous delivery. It is reported that MNs can facilitate delivery without stimulating the pain receptors or damaging blood vessels that lie beneath, thus being perceived as painless and associated with reduced bleeding. This immunocompetence of the skin, coupled with its ease of access, makes this organ an attractive vaccination site. The purpose of this review was to collate primary scientific literature pertaining to MN-mediated in vivo vaccination programmes. A total of 62 original research articles are presented, compiling vaccination strategies in 6 different models (mouse, rat, guinea pig, rabbit, pig, macaque and human). Vaccines tested span a wide range of viral, bacterial and protozoan pathogens and includes 7 of the 13 vaccine-preventable diseases, as defined by the WHO. This review highlights the paucity of available clinical trial data. MN-delivered vaccines have demonstrated safety and immunogenicity in pre-clinical models and boast desirable attributes such as painless administration, thermostability, dose-sparing capacity and the potential for self-administration. These advantages should contribute to enhanced global vaccine access.

Understanding parental attitudes to their children’s vaccination is critical to developing and implementing interventions that address parents’ hesitancy and improve vaccine uptake. The Parent Attitudes about Childhood Vaccines (PACV) survey is a validated tool for identifying vaccine hesitancy in parents. We evaluated the rate of vaccine hesitancy and areas of concern regarding childhood vaccinations using an adapted version of the PACV survey, in a convenience sample of parents attending a STEM (Science, Technology, Engineering and Mathematics) outreach event in Ireland, in 2018. A score ≥ 50 identified vaccine hesitant parents. Of 105 parents who completed the survey, the prevalence of vaccine hesitancy was 6.7%, (7/105). Parents had concerns around vaccine side effects (36.2%, n = 38), vaccine safety (20%, n = 21) and the number of vaccines administered (13.3%, n = 14). Parents trusted the vaccine information they received (85.6%, n = 90) and 81.9% (n = 86) believed that the vaccine schedule was good for their child. The findings indicate the presence of vaccine hesitancy in parents in Ireland regarding paediatric vaccines with further research necessary to address parents’ vaccine concerns. Future research should explore further, by qualitative methods, parents’ vaccine concerns. There is also potential to identify vaccine hesitant parents with the PACV survey as a surveillance method in healthcare settings; for example, in community pharmacies, family doctor clinics and out-patient clinics.