Acceptability of an inactivated influenza vaccine delivered by microneedle patch: Results from a phase I clinical trial of safety, reactogenicity, and immunogenicity

Perceptions of non-needle-based vaccination devices in the state of Georgia

BACKGROUND

Vaccination is important for controlling infectious disease; however, there are logistical barriers associated with needle and syringe-based vaccination. Non-needle-based vaccination methods could address many of these barriers and are in pre-clinical and clinical development. New technology is sometimes followed by hesitancy, affecting acceptance and uptake, highlighting the importance of understanding the perceptions of vaccine delivery methods by potential vaccine recipients.

METHODS

To understand perceptions of non-needle-based vaccination methods in the state of Georgia, we surveyed 427 Georgia residents. Respondents were asked about their perceptions of vaccines and new medical technology, willingness to accept a non-needle-based vaccine, and whether they would recommend specific vaccination devices.

RESULTS

Race and ethnicity were found to impact vaccine hesitancy and trust in new medical developments hesitancy. Of 427 participants, 29.3 % were more likely to accept non-needle-based devices over needle/syringe, 35.1 % were just as likely to accept, 14.4 % were unsure, and 20.6 % indicated that non-needle-based methods would not make them more likely to receive a vaccine. Race, urbanization, insurance status, vaccine hesitancy, and trust in new medical developments affected willingness to accept a non-needle-based vaccine. Needle/syringe vaccine devices were the most accepted method based on a picture and short description (77.6 %), inhaled vaccine devices were the least recommended (46.8 %); nasal spray (64.3 %), jet injector (60.0 %), skin patch (57.3 %), and oral delivery (54.0 %) were between these values.

CONCLUSIONS

While needle/syringe is the preferred method of vaccination, there are clear preferences among non-needle-based vaccine delivery methods; however, demographic factors that are associated should be considered as these devices move through clinical testing. Our future work will involve in-depth interviews to further identify important themes affecting vaccine acceptance in Georgia. Due to potential hesitancy, we need to strengthen our understanding of themes associated with vaccine perceptions to enable design of accurate and persuasive materials for physicians and patients.

Enhancing vaccine stability in transdermal microneedle platforms

Micron-scale needles, so-called microneedles (MNs) offer a minimally invasive, nearly painless, and user-friendly method for effective intradermal immunization. Maintaining the stability of antigens and therapeutics is the primary challenge in producing vaccine or drug-loaded MNs. The manufacturing of MNs patches involves processes at ambient or higher temperatures and various physio-mechanical stresses that can impact the therapeutic efficacy of sensitive biologics or vaccines. Therefore, it is crucial to develop techniques that safeguard vaccines and other biological payloads within MNs. Despite growing research interest in deploying MNs as an efficient tool for delivering vaccines, there is no comprehensive review that integrates the strategies and efforts to preserve the thermostability of vaccine payloads to ensure compatibility with MNs fabrication. The discussion delves into various physical and chemical approaches for stabilizing antigens in vaccine formulations, which are subsequently integrated into the MNs matrix. The primary focus is to comprehensively examine the challenges associated with the translation of thermostable vaccine MNs for clinical applications while considering a safe, cost-effective approach with a regulatory roadmap. The recent cutting-edge advances facilitating flexible and scalable manufacturing of stabilized MNs patches have been emphasized. In conclusion, the ability to stabilize vaccines and therapeutics for MNs applications could bolster the effectiveness, safety and user-compliance for various drugs and vaccines, potentially offering a substantial impact on global public health.

Rapidly separable bubble microneedle-patch system present superior transdermal mRNA delivery efficiency

Traditional mRNA vaccine formulation loaded by lipid nanoparticle (mRNA-LNP) has several shortcomings in clinical application, including the need for cryopreservation, discomfort associated with intramuscular injections, and the risk of liver aggregation. Dissolvable microneedles (DMNs), as a novel transdermal drug delivery platform, can overcome the skin barrier to deliver drugs directly into the skin in a minimally invasive manner. However, mRNA-LNP is unstable and easily degraded during the solidification of DMN. In this study, we proposed to establish a rapidly dissolvable bubble microneedle patch (bMNP) system for the transdermal delivery of mRNA-LNP. We explored to use polyvinyl alcohol (PVA) and trehalose for the first time as matrix material for preparing microneedles. Our results demonstrate that the stability of the mRNA-LNP was obviously improved. The mRNA in this bMNP system can be stored at room temperature for at least one month. Furthermore, the existence of air bubbles between the needle tip and the dorsal scale of bMNP can achieve dorsal scale separation by applying shear force after inserting into subcutaneous tissue, and effectively target lymph nodes in vivo after releasing mRNA-LNP. Using mRNA that encodes the spike protein from SARS-CoV-2 as a test case, the rapidly separable bMNP system induced the production of significant levels of spike-specific IgG antibodies, neutralizing antibodies, and a Th1-polarized T cell response, providing an alternative route for mRNA delivery. Our research is expected to provide a promising transdermal drug delivery strategy that can improve mRNA vaccine accessibility.

The Long-Term Immunity of a Microneedle Array Patch of a SARS-CoV-2 S1 Protein Subunit Vaccine Irradiated by Gamma Rays in Mice

BACKGROUND/OBJECTIVES

COVID-19 vaccines effectively prevent severe disease, but unequal distribution, especially in low- and middle-income countries, has led to vaccine-resistant strains. This highlights the urgent need for alternative vaccine platforms that are safe, thermostable, and easy to distribute. This study evaluates the immunogenicity, stability, and scalability of a dissolved microneedle array patch (MAP) delivering the rS1RS09 subunit vaccine, comprising the SARS-CoV-2 S1 monomer and RS09, a TLR-4 agonist peptide.

METHODS

The rS1RS09 vaccine was administered via MAP or intramuscular injection in murine models. The immune responses of the MAP with and without gamma irradiation as terminal sterilization were assessed at doses of 5, 15, and 45 µg, alongside neutralizing antibody responses to Wuhan, Delta, and Omicron variants. The long-term storage stability was also evaluated through protein degradation analyses at varying temperatures.

RESULTS

The rS1RS09 vaccine elicited stronger immune responses and ACE2-binding inhibition than S1 monomer alone or trimer. The MAP delivery induced sgnificantly higher and longer-lasting S1-specific IgG responses for up to 70 weeks compared to intramuscular injections. Robust Th2-prevalent immune responses were generated in all the groups vaccinated via the MAP and significant neutralizing antibodies were elicited at 15 and 45 µg, showing dose-sparing potential. The rS1RS09 in MAP has remained stable with minimal protein degradation for 19 months at room temperature or under refrigeration, regardless of gamma-irradiation. After an additional month of storage at 42 °C, cit showed less than 3% degradation, ompared to over 23% in liquid vaccines Conclusions: Gamma-irradiated MAP-rS1RS09 is a promising platform for stable, scalable vaccine production and distribution, eliminating cold chain logistics. These findings support its potential for mass vaccination efforts, particularly in resource-limited settings.

Multi-Layered Microneedles Loaded with Microspheres

Delivery of therapies into skin is attractive for medical indications including vaccination and treatment of dermatoses but is highly constrained by the stratum corneum barrier. Microneedle (MN) patches have emerged as a promising technology to enable non-invasive, intuitive, and low-cost skin delivery. When combined with biodegradable polymer formulations, MN patches can further enable controlled-release drug delivery without injection. Herein, we sought to expand on the capability of MN patches to deliver therapies into skin by providing improved spatiotemporal control. Polylactic-co-glycolic acid (PLGA) microspheres were used to encapsulate model dye and then loaded into MN patches through a layer-by-layer fabrication method that created multiple layers of different composition within each MN. MN patches were loaded with up to 5 μg/MN of PLGA microspheres. Mechanical testing demonstrated that mechanical strength of MNs decreased with increasing number of microsphere layers. Microsphere-loaded MN patches inserted into porcine skin ex vivo and murine skin in vivo fully dissolved within 15 min, administering drug-loaded microspheres for controlled release lasting over 45 days. These data support the feasibility of multi-layered, microsphere-loaded MN patches designed for spatially targeted and sustained delivery of therapies into skin.

Current Status of Microneedle Array Technology for Therapeutic Delivery: From Bench to Clinic

In recent years, microneedle (MN) patches have emerged as an alternative technology for transdermal delivery of various drugs, therapeutics proteins, and vaccines. Therefore, there is an urgent need to understand the status of MN-based therapeutics. The article aims to illustrate the current status of microneedle array technology for therapeutic delivery through a comprehensive review. However, the PubMed search was performed to understand the MN's therapeutics delivery status. At the same time, the search shows the number no of publications on MN is increasing (63). The search was performed with the keywords "Coated microneedle," "Hollow microneedle," "Dissolvable microneedle," and "Hydrogel microneedle," which also shows increasing trend. Similarly, the article highlighted the application of different microneedle arrays for treating different diseases. The article also illustrated the current status of different phases of MN-based therapeutics clinical trials. It discusses the delivery of different therapeutic molecules, such as drug molecule delivery, using microneedle array technology. The approach mainly discusses the delivery of different therapeutic molecules. The leading pharmaceutical companies that produce the microneedle array for therapeutic purposes have also been discussed. Finally, we discussed the limitations and future prospects of this technology.

An Application of an Initial Full Value of Vaccine Assessment Methodology to Measles-Rubella MAPs for Use in Low- and Middle-Income Countries

Measles and rubella micro-array patches (MR-MAPs) are a promising innovation to address limitations of the current needle and syringe (N&S) presentation due to their single-dose presentation, ease of use, and improved thermostability. To direct and accelerate further research and interventions, an initial full value vaccine assessment (iFVVA) was initiated prior to MR-MAPs entering phase I trials to quantify their value and identify key data gaps and challenges. The iFVVA utilized a mixed-methods approach with rapid assessment of literature, stakeholder interviews and surveys, and quantitative data analyses to (i) assess global need for improved MR vaccines and how MR-MAPs could address MR problem statements; (ii) estimate costs and benefits of MR-MAPs; (iii) identify the best pathway from development to delivery; and (iv) identify outstanding areas of need where stakeholder intervention can be helpful. These analyses found that if MR-MAPs are broadly deployed, they can potentially reach an additional 80 million children compared to the N&S presentation between 2030-2040. MR-MAPs can avert up to 37 million measles cases, 400,000 measles deaths, and 26 million disability-adjusted life years (DALYs). MR-MAPs with the most optimal product characteristics of low price, controlled temperature chain (CTC) properties, and small cold chain volumes were shown to be cost saving for routine immunization (RI) in low- and middle-income countries (LMICs) compared to N&S. Uncertainties about price and future vaccine coverage impact the potential cost-effectiveness of introducing MR-MAPs in LMICs, indicating that it could be cost-effective in 16-81% of LMICs. Furthermore, this iFVVA highlighted the importance of upfront donor investment in manufacturing set-up and clinical studies and the critical influence of an appropriate price to ensure country and manufacturer financial sustainability. To ensure that MR-MAPs achieve the greatest public health benefit, MAP developers, vaccine manufacturers, donors, financiers, and policy- and decision-makers will need close collaboration and open communications.

Microneedle system for tissue engineering and regenerative medicines: a smart and efficient therapeutic approach

The global demand for an enhanced quality of life and extended lifespan has driven significant advancements in tissue engineering and regenerative medicine. These fields utilize a range of interdisciplinary theories and techniques to repair structurally impaired or damaged tissues and organs, as well as restore their normal functions. Nevertheless, the clinical efficacy of medications, materials, and potent cells used at the laboratory level is always constrained by technological limitations. A novel platform known as adaptable microneedles has been developed to address the abovementioned issues. These microneedles offer a solution for the localized distribution of various cargos while minimizing invasiveness. Microneedles provide favorable patient compliance in clinical settings due to their effective administration and ability to provide a painless and convenient process. In this review article, we summarized the most recent development of microneedles, and we started by classifying various microneedle systems, advantages, and fundamental properties. Subsequently, it provides a comprehensive overview of different types of microneedles, the material used to fabricate microneedles, the fundamental properties of ideal microneedles, and their applications in tissue engineering and regenerative medicine, primarily focusing on preserving and restoring impaired tissues and organs. The limitations and perspectives have been discussed by concluding their future therapeutic applications in tissue engineering and regenerative medicines.

Self-Implantable Core-Shell Microneedle Patch for Long-Acting Treatment of Keratitis via Programmed Drug Release

Bacteria-induced keratitis is a major cause of corneal blindness in both developed and developing countries. Instillation of antibiotic eyedrops is the most common management of bacterial keratitis but usually suffers from low bioavailability (i.e., <5%) and frequent administration, due to the existence of corneal epithelial barrier that prevents large and hydrophilic drug molecules from entering the cornea, and the tear film on corneal surface that rapidly washes drug away from the cornea. Here, a self-implantable core-shell microneedle (MN) patch with programmed drug release property to facilitate bacterial keratitis treatment is reported. The pH-responsive antimicrobial nanoparticles (NPs), Ag@ZIF-8, which are capable of producing antibacterial metal ions in the infected cornea and generating oxidative stress in bacteria, are loaded in the dissolvable core, while the anti-angiogenic drug, rapamycin (Rapa), is encapsulated in the biodegradable shell, thereby enabling rapid release of Ag@ZIF-8 NPs and sustained release of Rapa after corneal insertion. Owing to the programmed release feature, one single administration of the core-shell MN patch in a rat model of bacterial keratitis, can achieve satisfactory antimicrobial activity and superior anti-angiogenic and anti-inflammation effects as compared to daily topical eyedrops, indicating a great potential for the infectious keratitis therapy in clinics.

Design of a Novel Delivery Efficiency Feedback System for Biphasic Dissolving Microarray Patches Based on Poly(Lactic Acid) and Moisture-Indicating Silica

Dissolving microarray patches (DMAPs) represent an innovative approach to minimally invasive transdermal drug delivery, demonstrating efficacy in delivering both small and large therapeutic molecules. However, concerns raised in end-user surveys have hindered their commercialization efforts. One prevalent issue highlighted in these surveys is the lack of clear indicators for successful patch insertion and removal time. To address this challenge, a color-change-based feedback system is devised, which confirms the insertion and dissolution of DMAPs, aiming to mitigate the aforementioned problems. The approach combines hydrophilic needles containing model drugs (fluorescein sodium and fluorescein isothiocyanate (FITC)-dextran) with a hydrophobic poly(lactic acid) baseplate infused with moisture-sensitive silica gel particles. The successful insertion and subsequent complete dissolution of the needle shaft are indicated by the progressive color change of crystal violet encapsulated in the silica. Notably, distinct color alterations on the baseplate, observed 30 min and 1 h after insertion for FITC-dextran and fluorescein sodium DMAPs respectively, signal the full dissolution of the needles, confirming the complete cargo delivery and enabling timely patch removal. This innovative feedback system offers a practical solution for addressing end-user concerns and may significantly contribute to the successful commercialization of DMAPs by providing a visualized drug delivery method.

Developing and validating a scale to measure the perceptions of safety, usability and acceptability of microarray patches for vaccination: a study protocol

Background

Vaccination is a fundamental tenet of public and population health. Several barriers to vaccine uptake exist, exacerbated post-COVID-19, including misconceptions about vaccine efficacy and safety, vaccine hesitancy, vaccine inequity, costs, religious beliefs, and insufficient education and guidance for healthcare professionals. Vaccine uptake may be aided using microarray patches (MAPs) due to reduced pain, no hypodermic needle, enhanced thermostability, and potential for self and lay administration.

Objectives

This protocol outlines the development of a scale that aims to accurately measure the perceived safety, usability, and acceptability of MAPs for vaccination among laypeople, MAP recipients, clinicians, and parents or guardians of children.

Methods and analysis

This study will follow three phases of scale development and validation, including (1) item development, (2) scale development, and (3) scale evaluation. Inductive (interviews) and deductive methods (literature searches) will be used to develop scale items, which experts from target populations will assess through an online survey. Cognitive interviews will be conducted to observe their processes of answering the draft survey. Thematic analysis will be conducted to analyse qualitative data. Lastly, four surveys will be administered online to our target populations over two time points to determine their repeatability. Exploratory and confirmatory factor analyses, Cronbach's alpha, and construct validity will be performed.

Ethics

This study was approved by Metro South Health (HREC/2021/QMS/81653) and Western Sydney Local Health District (2023/ETH00705) Human Research Ethics Committees.

Discussion

The scale will support a standardised approach to assessing the social and behavioural aspects of MAP vaccines, enabling comparison of outcomes across studies. Once validated, this scale will assist vaccination programmes in developing effective strategies for integrating MAPs and overcoming barriers to vaccination. This includes improving vaccine equity and accessibility, especially in lower- and middle-income countries and rural or remote locations.

Advancing immunotherapy using biomaterials to control tissue, cellular, and molecular level immune signaling in skin

Immunotherapies have been transformative in many areas, including cancer treatments, allergies, and autoimmune diseases. However, significant challenges persist in extending the reach of these technologies to new indications and patients. Some of the major hurdles include narrow applicability to patient groups, transient efficacy, high cost burdens, poor immunogenicity, and side effects or off-target toxicity that results from lack of disease-specificity and inefficient delivery. Thus, there is a significant need for strategies that control immune responses generated by immunotherapies while targeting infection, cancer, allergy, and autoimmunity. Being the outermost barrier of the body and the first line of host defense, the skin presents a unique immunological interface to achieve these goals. The skin contains a high concentration of specialized immune cells, such as antigen-presenting cells and tissue-resident memory T cells. These cells feature diverse and potent combinations of immune receptors, providing access to cellular and molecular level control to modulate immune responses. Thus, skin provides accessible tissue, cellular, and molecular level controls that can be harnessed to improve immunotherapies. Biomaterial platforms - microneedles, nano- and micro-particles, scaffolds, and other technologies - are uniquely capable of modulating the specialized immunological niche in skin by targeting these distinct biological levels of control. This review highlights recent pre-clinical and clinical advances in biomaterial-based approaches to target and modulate immune signaling in the skin at the tissue, cellular, and molecular levels for immunotherapeutic applications. We begin by discussing skin cytoarchitecture and resident immune cells to establish the biological rationale for skin-targeting immunotherapies. This is followed by a critical presentation of biomaterial-based pre-clinical and clinical studies aimed at controlling the immune response in the skin for immunotherapy and therapeutic vaccine applications in cancer, allergy, and autoimmunity.

Polymeric Microneedles for Health Care Monitoring: An Emerging Trend

Bioanalyte collection by blood draw is a painful process, prone to needle phobia and injuries. Microneedles can be engineered to penetrate the epidermal skin barrier and collect analytes from the interstitial fluid, arising as a safe, painless, and effective alternative to hypodermic needles. Although there are plenty of reviews on the various types of microneedles and their use as drug delivery systems, there is a lack of systematization on the application of polymeric microneedles for diagnosis. In this review, we focus on the current state of the art of this field, while providing information on safety, preclinical and clinical trials, and market distribution, to outline what we believe will be the future of health monitoring.

Targeting Diverse Wounds and Scars: Recent Innovative Bio-design of Microneedle Patch for Comprehensive Management

Wounds and the subsequent formation of scars constitute a unified and complex phased process. Effective treatment is crucial; however, the diverse therapeutic approaches for different wounds and scars, as well as varying treatment needs at different stages, present significant challenges in selecting appropriate interventions. Microneedle patch (MNP), as a novel minimally invasive transdermal drug delivery system, has the potential for integrated and programmed treatment of various diseases and has shown promising applications in different types of wounds and scars. In this comprehensive review, the latest applications and biotechnological innovations of MNPs in these fields are thoroughly explored, summarizing their powerful abilities to accelerate healing, inhibit scar formation, and manage related symptoms. Moreover, potential applications in various scenarios are discussed. Additionally, the side effects, manufacturing processes, and material selection to explore the clinical translational potential are investigated. This groundwork can provide a theoretical basis and serve as a catalyst for future innovations in the pursuit of favorable therapeutic options for skin tissue regeneration.

Exploiting Unique Features of Microneedles to Modulate Immunity

Microneedle arrays (MNAs) are small patches containing hundreds of short projections that deliver signals directly to dermal layers without causing pain. These technologies are of special interest for immunotherapy and vaccine delivery because they directly target immune cells concentrated in the skin. The targeting abilities of MNAs result in efficient immune responses-often more protective or therapeutic-compared to conventional needle delivery. MNAs also offer logistical benefits, such as self-administration and transportation without refrigeration. Thus, numerous preclinical and clinical studies are exploring these technologies. Here the unique advantages of MNA, as well as critical challenges-such as manufacturing and sterility issues-the field faces to enable widespread deployment are discussed. How MNA design parameters can be exploited for controlled release of vaccines and immunotherapies, and the application to preclinical models of infection, cancer, autoimmunity, and allergies are explained. Specific strategies are also discussed to reduce off-target effects compared to conventional vaccine delivery routes, and novel chemical and manufacturing controls that enable cargo stability in MNAs across flexible intervals and temperatures. Clinical research using MNAs is then examined. Drawbacks of MNAs and the implications, and emerging opportunities to exploit MNAs for immune engineering and clinical use are concluded.

Chitosan-Alginate Polymeric Nanocomposites as a Potential Oral Vaccine Carrier Against Influenza Virus Infection

Lessons from the recent COVID-19 pandemic underscore the importance of rapidly developing an efficacious vaccine and its immediate administration for prophylaxis. Oral vaccines are of particular interest, as the presence of healthcare professionals is not needed for this stress-free vaccination approach. In this study, we designed a chitosan (CH)-alginate (AL) complex carrier system encapsulating an inactivated influenza virus vaccine (A/PR/8/34, H1N1), and the efficacy of these orally administered nanocomposite vaccines was evaluated in mice. Interestingly, CH-AL complexes were able to load large doses of vaccine (≥90%) with a stable dispersion. The encapsulated vaccine was protected from gastric acid and successfully released from the nanocomposite upon exposure to conditions resembling those of the small intestines. Scanning electron microscopy of the CH-virus-AL complexes revealed that the connections between the lumps became loose and widened pores were visible on the nanocomposite's surface at pH 7.4, thereby increasing the chance of virus release into the surroundings. Orally inoculating CH-virus-AL into mice elicited higher virus-specific IgG compared to the unimmunized controls. CH-virus-AL immunization also enhanced CD4 and CD8 T cell responses while diminishing lung virus titer, inflammatory cytokine production, and body weight loss compared to the infection control group. These results suggest that chitosan-alginate polymeric nanocomposites could be promising delivery complexes for oral influenza vaccines.

Microneedle-Mediated Immunization Promotes Lung CD8+ T-Cell Immunity

Microneedle array has proven more efficient in stimulating humoral immunity than intramuscular vaccination. However, its effectiveness in inducing pulmonary CD8+ T cells remains elusive, which is essential to the frontline defense against pulmonary viral infections such as influenza and COVID-19 viruses. The current investigation reveals that superior CD8+ T-cell responses are elicited by immunization with a microneedle array over intradermal or intramuscular immunization using the model antigen ovalbumin, irrespective of whether or not the antigen is provided in the lung. Mechanistically, microneedle array-mediated immunization targeted the epidermal layer and stimulated predominantly Langerhans cells, resulting in increased expression of α4β1 adhesion molecules on the CD8+ T-cell surface, which may play a role in T-cell homing to the lung, whereas CD8+ T cells induced by intramuscular immunization did not express the adhesion molecule sufficiently. CD8+ T cells with a lung-homing propensity were also seen after intradermal vaccination, yet to a much lesser extent. Accordingly, microneedle array immunization provided stronger protection against influenza viral infection than intradermal or intramuscular immunization. The observations offer insights into a strong cross-talk between epidermal immunization and lung immunity and are valuable for designing and delivering vaccines against respiratory viral infections.

Immunogenicity, safety, usability and acceptability of microarray patches for vaccination: a systematic review and meta-analysis

BACKGROUND

Microarray patches (MAPs) deliver vaccines to the epidermis and the upper dermis, where abundant immune cells reside. There are several potential benefits to using MAPs, including reduced sharps risk, thermostability, no need for reconstitution, tolerability and self-administration. We aimed to explore and evaluate the immunogenicity, safety, usability and acceptability of MAPs for vaccination.

METHODS

We searched CINAHL, Cochrane Library, Ovid Embase, Ovid MEDLINE and Web of Science from inception to January 2023. Eligibility criteria included all research studies in any language, which examined microarrays or microneedles intended or used for vaccination and explored immunogenicity, safety, usability or acceptability in their findings. Two reviewers conducted title and abstract screening, full-text reviewing and data extraction.

RESULTS

Twenty-two studies were included (quantitative=15, qualitative=2 and mixed methods=5). The risk of bias was mostly low, with two studies at high risk of bias. Four clinical trials were included, three using influenza antigens and one with Japanese encephalitis delivered by MAP. A meta-analysis indicated similar or higher immunogenicity in influenza MAPs compared with needle and syringe (N&S) (standardised mean difference=10.80, 95% CI: 3.51 to 18.08, p<0.00001). There were no significant differences in immune cell function between MAPs and N&S. No serious adverse events were reported in MAPs. Erythema was more common after MAP application than N&S but was brief and well tolerated. Lower pain scores were usually reported after MAP application than N&S. Most studies found MAPs easy to use and highly acceptable among healthcare professionals, laypeople and parents.

CONCLUSION

MAPs for vaccination were safe and well tolerated and evoked similar or enhanced immunogenicity than N&S, but further research is needed. Vaccine uptake may be increased using MAPs due to less pain, enhanced thermostability, layperson and self-administration. MAPs could benefit at-risk groups and low and middle-income countries.

PROSPERO REGISTRATION NUMBER

CRD42022323026.

Microneedle-Mediated Transcutaneous Immunization: Potential in Nucleic Acid Vaccination

Efforts aimed at exploring economical and efficient vaccination have taken center stage to combat frequent epidemics worldwide. Various vaccines have been developed for infectious diseases, among which nucleic acid vaccines have attracted much attention from researchers due to their design flexibility and wide application. However, the lack of an efficient delivery system considerably limits the clinical translation of nucleic acid vaccines. As mass vaccinations via syringes are limited by low patient compliance and high costs, microneedles (MNs), which can achieve painless, cost-effective, and efficient drug delivery, can provide an ideal vaccination strategy. The MNs can break through the stratum corneum barrier in the skin and deliver vaccines to the immune cell-rich epidermis and dermis. In addition, the feasibility of MN-mediated vaccination is demonstrated in both preclinical and clinical studies and has tremendous potential for the delivery of nucleic acid vaccines. In this work, the current status of research on MN vaccines is reviewed. Moreover, the improvements of MN-mediated nucleic acid vaccination are summarized and the challenges of its clinical translation in the future are discussed.

Tuning innate immune function using microneedles containing multiple classes of toll-like receptor agonists

Microneedle arrays (MNAs) are patches displaying hundreds of micron-scale needles that can penetrate skin. As a result, these arrays efficiently and painlessly access this immune cell-rich niche, motivating significant clinical interest in MNA-based vaccines. Our lab has developed immune polyelectrolyte multilayers (iPEMs), nanostructures built entirely from immune signals employing electrostatic self-assembly. iPEMs consist of positively charged peptide antigen and negatively charged toll-like receptor agonists (TLRas) to assemble these components at ultra-high density since no carrier is needed. Here we used this technology to deliver MNAs with antigen and defined ratios of multiple classes of TLRa. Notably, this approach resulted in facile assembly and corresponding signal transduction through each respective TLR pathway. This control ultimately activated primary antigen presenting cells and drove proliferation of antigen-specific T cells. In related in vivo vaccine studies, application of MNAs resulted in distinct T cells response depending on the number of TLRa classes delivered with MNAs. These MNAs technologies create an opportunity to deliver nanostructured vaccine components at high density, and to probe integration of multiple TLRas in skin to tune immunity.

Responsive Microneedles as a New Platform for Precision Immunotherapy

Microneedles are a well-known transdermal or transdermal drug delivery system. Different from intramuscular injection, intravenous injection, etc., the microneedle delivery system provides unique characteristics for immunotherapy administration. Microneedles can deliver immunotherapeutic agents to the epidermis and dermis, where immune cells are abundant, unlike conventional vaccine systems. Furthermore, microneedle devices can be designed to respond to certain endogenous or exogenous stimuli including pH, reactive oxygen species (ROS), enzyme, light, temperature, or mechanical force, thereby allowing controlled release of active compounds in the epidermis and dermis. In this way, multifunctional or stimuli-responsive microneedles for immunotherapy could enhance the efficacy of immune responses to prevent or mitigate disease progression and lessen systemic adverse effects on healthy tissues and organs. Since microneedles are a promising drug delivery system for accurate delivery and controlled drug release, this review focuses on the progress of using reactive microneedles for immunotherapy, especially for tumors. Limitations of current microneedle system are summarized, and the controllable administration and targeting of reactive microneedle systems are examined.

Microneedles: An Emerging Vaccine Delivery Tool and a Prospective Solution to the Challenges of SARS-CoV-2 Mass Vaccination

Vaccination is an effective measure to prevent infectious diseases. Protective immunity is induced when the immune system is exposed to a vaccine formulation with appropriate immunogenicity. However, traditional injection vaccination is always accompanied by fear and severe pain. As an emerging vaccine delivery tool, microneedles overcome the problems associated with routine needle vaccination, which can effectively deliver vaccines rich in antigen-presenting cells (APCs) to the epidermis and dermis painlessly, inducing a strong immune response. In addition, microneedles have the advantages of avoiding cold chain storage and have the flexibility of self-operation, which can solve the logistics and delivery obstacles of vaccines, covering the vaccination of the special population more easily and conveniently. Examples include people in rural areas with restricted vaccine storage facilities and medical professionals, elderly and disabled people with limited mobility, infants and young children afraid of pain. Currently, in the late stage of fighting against COVID-19, the main task is to increase the coverage of vaccines, especially for special populations. To address this challenge, microneedle-based vaccines have great potential to increase global vaccination rates and save many lives. This review describes the current progress of microneedles as a vaccine delivery system and its prospects in achieving mass vaccination against SARS-CoV-2.

Skin-Based Vaccination: A Systematic Mapping Review of the Types of Vaccines and Methods Used and Immunity and Protection Elicited in Pigs

The advantages of skin-based vaccination include induction of strong immunity, dose-sparing, and ease of administration. Several technologies for skin-based immunisation in humans are being developed to maximise these key advantages. This route is more conventionally used in veterinary medicine. Skin-based vaccination of pigs is of high relevance due to their anatomical, physiological, and immunological similarities to humans, as well as being a source of zoonotic diseases and their livestock value. We conducted a systematic mapping review, focusing on vaccine-induced immunity and safety after the skin immunisation of pigs. Veterinary vaccines, specifically anti-viral vaccines, predominated in the literature. The safe and potent skin administration to pigs of adjuvanted vaccines, particularly emulsions, are frequently documented. Multiple methods of skin immunisation exist; however, there is a lack of consistent terminology and accurate descriptions of the route and device. Antibody responses, compared to other immune correlates, are most frequently reported. There is a lack of research on the underlying mechanisms of action and breadth of responses. Nevertheless, encouraging results, both in safety and immunogenicity, were observed after skin vaccination that were often comparable to or superior the intramuscular route. Further research in this area will underlie the development of enhanced skin vaccine strategies for pigs, other animals and humans.

Recent Updates in Vaccine Delivery through Microneedles

Recent coronavirus pandemic and its global socio-economic impact has re-emphasized the need for safe, fast, and efficient delivery of vaccines for humankind. With advent of technological advances, and to improve patient acquiescence, several techniques for fast, effective, and safe delivery of vaccines have been researched and published in the literature in last three decades. These delivery enhancement techniques include but are not limited to electroporation, microneedles (MN), ultrasound, iontophoresis, etc. This review aims at discussing the current research undergoing in vaccine delivery, specifically focusing on microneedles assisted, the historical background of microneedles and their introduction to drug delivery area, and a special focus on formulation challenges and stability in these systems. The review also sheds light on regulatory challenges one must keep in mind for bringing a successful microneedles-based vaccine delivery into market as well as a snapshot of current commercially available microneedles-based products in cosmetic and pharmaceutical industry.

Microarray patches: scratching the surface of vaccine delivery

INTRODUCTION

Microneedles are emerging as a promising technology for vaccine delivery, with numerous advantages over traditional needle and syringe methods. Preclinical studies have demonstrated the effectiveness of MAPs in inducing robust immune responses over traditional needle and syringe methods, with extensive studies using vaccines targeted against different pathogens in various animal models. Critically, the clinical trials have demonstrated safety, immunogenicity, and patient acceptance for MAP-based vaccines against influenza, measles, rubella, and SARS-CoV-2.

AREAS COVERED

This review provides a comprehensive overview of the different types of microarray patches (MAPs) and analyses of their applications in preclinical and clinical vaccine delivery settings. This review also covers additional considerations for microneedle-based vaccination, including adjuvants that are compatible with MAPs, patient safety and factors for global vaccination campaigns.

EXPERT OPINION

MAP vaccine delivery can potentially be a game-changer for vaccine distribution and coverage in both high-income and low- and middle-income countries. For MAPs to reach this full potential, many critical hurdles must be overcome, such as large-scale production, regulatory compliance, and adoption by global health authorities. However, given the considerable strides made in recent years by MAP developers, it may be possible to see the first MAP-based vaccines in use within the next 5 years.

Opportunities and challenges for commercializing microarray patches for vaccination from a MAP developer's perspective

Continued advances in microarray patch (MAP) technology are starting to make needle-free delivery of a broad range of vaccines an achievable goal. The drivers and potential benefits of a MAP platform for pandemic response and routine vaccination are clear and include dose-sparing, cold-chain elimination, increased safety, and potential self-administration. MAP technology is regarded as a priority innovation to overcome vaccination barriers, ensure equitable access, and improve the effectiveness of vaccines. Vaxxas, a global leader in this technology, has built a strong evidence-base for the commercial application of their high-density (HD) MAP platform, and is rapidly advancing scale-up of the manufacturing process for HD-MAPs. A greater awareness and understanding of the implications of the technology amongst supply-chain participants, regulatory authorities, and global healthcare organizations and foundations is needed to accelerate adoption and, particularly, to prepare for MAP use in pandemics. Key challenges remain in the commercialization of MAP technology and its adoption, including market acceptance, scale-up of production, regulatory approval, and the availability of capital to build advanced manufacturing infrastructure ahead of late-stage clinical trials.

Transcutaneous immunization via dissolving microneedles protects mice from lethal influenza H7N9 virus challenge

Avian influenza H7N9 virus has first emerged in 2013 and since then has spread in China in five seasonal waves. In humans, influenza H7N9 virus infection is associated with a high fatality rate; thus, an effective vaccine for this virus is needed. In the present study, we evaluated the usefulness of dissolving microneedles (MNs) loaded with influenza H7N9 vaccine in terms of the dissolution time, insertion capacity, insertion depth, and structural integrity of H7N9 virus in vitro. Our in vitro results showed MNs dissolved within 6 mins. The depth of skin penetration was 270 µm. After coating with a matrix material solution, the H7N9 proteins were agglomerated. We detected the H7N9 delivery time and humoral immune response in vivo. In a mouse model, the antigen retention time was longer for MNs than for intramuscular (IM) injection. The humoral response showed that similar to IM administration, MN administration increased the levels of functional and systematic antibodies and protection against the live influenza A/Anhui/01/2013 virus (Ah01/H7N9). The protection level was determined by the analysis of pathological sections of infected lungs. MN and IM administration yielded results superior to those in the control group. Taken together, these findings demonstrate that the use of dissolving MNs to deliver influenza H7N9 vaccines is a promising immunization approach.

Development of the H3N2 influenza microneedle vaccine for cross-protection against antigenic variants

Due to the continuously mutating nature of the H3N2 virus, two aspects were considered when preparing the H3N2 microneedle vaccines: (1) rapid preparation and (2) cross-protection against multiple antigenic variants. Previous methods of measuring hemagglutinin (HA) content required the standard antibody, thus rapid preparation of H3N2 microneedle vaccines targeting the mutant H3N2 was delayed as a result of lacking a standard antibody. In this study, H3N2 microneedle vaccines were prepared by high performance liquid chromatography (HPLC) without the use of an antibody, and the cross-protection of the vaccines against several antigenic variants was observed. The HA content measured by HPLC was compared with that measured by ELISA to observe the accuracy of the HPLC analysis of HA content. The cross-protection afforded by the H3N2 microneedle vaccines was evaluated against several antigenic variants in mice. Microneedle vaccines for the 2019–20 seasonal H3N2 influenza virus (19–20 A/KS/17) were prepared using a dip-coating process. The cross-protection of 19–20 A/KS/17 H3N2 microneedle vaccines against the 2015–16 seasonal H3N2 influenza virus in mice was investigated by monitoring body weight changes and survival rate. The neutralizing antibody against several H3N2 antigenic variants was evaluated using the plaque reduction neutralization test (PRNT). HA content in the solid microneedle vaccine formulation with trehalose post-exposure at 40℃ for 24 h was 48% and 43% from the initial HA content by HPLC and ELISA, respectively. The vaccine was administered to two groups of mice, one by microneedles and the other by intramuscular injection (IM). In vivo efficacies in the two groups were found to be similar, and cross-protection efficacy was also similar in both groups. HPLC exhibited good diagnostic performance with H3N2 microneedle vaccines and good agreement with ELISA. The H3N2 microneedle vaccines elicited a cross-protective immune response against the H3N2 antigenic variants. Here, we propose the use of HPLC for a more rapid approach in preparing H3N2 microneedle vaccines targeting H3N2 virus variants.

Sustained delivery approaches to improving adaptive immune responses

The immune system is one of the most important, complex biological networks regulating and protecting human health. Its precise modulation can prevent deadly infections and fight cancer. Accordingly, prophylactic vaccines and cancer immunotherapies are some of the most powerful technologies to protect against potential dangers through training of the immune system. Upon immunization, activation and maturation of B and T cells of the adaptive immune system are necessary for development of proper humoral and cellular protection. Yet, the exquisite organization of the immune system requires spatiotemporal control over the exposure of immunomodulatory signals. For example, while the human immune system has evolved to develop immunity to natural pathogenic infections that often last for weeks, current prophylactic vaccination technologies only expose the immune system to immunomodulatory signals for hours to days. It has become clear that leveraging sustained release technologies to prolong immunogen and adjuvant exposure can increase the potency, durability, and quality of adaptive immune responses. Over the past several years, tremendous breakthroughs have been made in the design of novel biomaterials such as nanoparticles, microparticles, hydrogels, and microneedles that can precisely control and the presentation of immunomodulatory signals to the immune system. In this review, we discuss relevant sustained release strategies and their corresponding benefits to cellular and humoral responses.

Influenza vaccines: where we are, where we are going

PURPOSE OF REVIEW

Influenza vaccines are the most useful strategy for preventing influenza illness, especially in the setting of the COVID-19 pandemic. For the coming year (2021/2022) all vaccines will be quadrivalent and contain two influenza A strains [(H1N1)pdm09-like and (H3N2)-like viruses] and two influenza B strains (Victoria lineage-like and Yamagata lineage-like viruses). However, the currently licensed have suboptimal efficacy due to the emergence of new strains and vaccine production limitations. In this review, we summarize the current recommendations as well as new advancements in influenza vaccinations.

RECENT FINDINGS

Recent advances have been aimed at moving away from egg-based vaccines and toward cell culture and recombinant vaccines. This removes egg adaptations that decrease vaccine efficacy, removes the reliance on egg availability and decreases the time necessary to manufacture vaccines. However, even more radical changes are needed if we are to reach the ultimate goal of a universal vaccine capable of providing long-lasting protection against all or at least most influenza strains. We discuss various strategies, including using more stable influenza antigens such as the hemagglutinin stalk and internal proteins as well as new adjuvants, new vaccine formulations, and DNA/RNA-based vaccines that are currently being developed.

SUMMARY

The currently available vaccines have suboptimal efficacy and do not provide adequate protection against drifted and shifted strains. Thus, the development of a universal influenza vaccine that induces long-lasing immunity and protects against a broad range of strains is crucial.

Intradermal administration of influenza vaccine with trehalose and pullulan-based dissolving microneedle arrays

Most influenza vaccines are administered via intramuscular injection which has several disadvantages that might jeopardize the compliance of vaccinees. Intradermal administration of dissolving-microneedle-arrays (dMNAs) could serve as minimal invasive alternative to needle injections. However, during the production process of dMNAs antigens are subjected to several stresses, which may reduce their potency. Moreover, the needles need to have sufficient mechanical strength to penetrate the skin and subsequently dissolve effectively to release the incorporated antigen. Here, we investigated whether blends of trehalose and pullulan are suitable for the production of stable dMNA fulfilling these criteria. Our results demonstrate that production of trehalose/pullulan-based dMNAs rendered microneedles that were sharp and stiff enough to pierce into ex vivo human skin and subsequently dissolve within 15 min. The mechanical properties of the dMNAs were maintained well even after four weeks of storage at temperatures up to 37°C. In addition, immunization of mice with influenza antigens via both freshly prepared dMNAs and dMNAs after storage (four weeks at 4°C or 37°C) resulted in antibody titers of similar magnitude as found in intramuscularly injected mice and partially protected mice from influenza virus infection. Altogether, our results demonstrate the potential of trehalose/pullulan-based dMNAs as alternative dosage form for influenza vaccination.

Usability, acceptability, and feasibility of a High-Density Microarray Patch (HD-MAP) applicator as a delivery method for vaccination in clinical settings

Background

High-density microarray patch (HD-MAP) vaccines may increase vaccine acceptance and use. We aimed to ascertain whether professional immunizers (PIs) and other healthcare workers (HCWs) in Australia, a High-Income Country (HIC), found the HD-MAP applicator usable and acceptable for vaccine delivery.

Methods

This feasibility study recruited PIs and HCWs to administer/receive simulated HD-MAP administration, including via self-administration. We assessed usability against essential and desirable criteria. Participants completed a survey, rating their agreement to statements about HD-MAP administration. A subset also participated in an interview or focus group. Survey data were analyzed using descriptive statistics, and interviews were transcribed and subject to thematic analysis.

Results

We recruited 61 participants: 23 PIs and 38 HCWs. Findings indicated high usability and acceptability of HD-MAP use across both groups by a healthcare professional or trained user and for self-administration with safety measures in place. Most administrations met essential criteria, but PIs, on average, applied the HD-MAP for slightly less time than the required 10-seconds, which the HCWs achieved. PIs perceived safety concerns about home administration but found layperson self-administration acceptable in an emergency, pandemic, and rural or remote settings.

Conclusions

Participants found HD-MAP administration usable and acceptable. Usability and acceptability are likely to be improved through end-user education and training.

Professional immunizers and healthcare workers found high-density microarray patch devices highly usable and acceptable to administer vaccines.

HD-MAPs may have advantages over intramuscular injections in clinical settings and in pandemics.

Vaccination with HD-MAP may improve acceptance for those with needle-related anxiety.

Adverse events following influenza immunization: understanding the role of age and sex interactions

BACKGROUND

Reduction of adverse events following immunization (AEFI) could improve vaccine uptake. Evidence suggests sex and age affect AEFI rates but, with limited understanding of their interaction, groups at higher risk for adverse reaction cannot be identified.

RESEARCH DESIGN AND METHODS

Using deidentified data (n = 308,481) from Australians receiving influenza vaccinations in the 2020 calendar year, we analyzed the effects of independent predictors (i.e. age and sex), on experiencing an AEFI using logistic regression generalized additive modeling to capture any nonlinear relationships and adjusting for vaccine brand and concomitant vaccination.

RESULTS

The overall reaction rate was 5.5%. Modeling revealed significant effects of age (p < 0.001), sex (p < 0.001), and age × sex (p < 0.001). Females were more likely than males to experience AEFIs between 7.5 and 87.5 years of age and exhibited peak odds at about 53 years, while peak odds for males occurred in infancy.

CONCLUSION

The results suggest there is a need for targeting AEFI reduction in females, particularly in 30-70-year-olds, to improve the vaccination experience. The results further suggest that reducing concomitant vaccination and choosing less reactogenic vaccine brands could reduce risk of AEFI, however, retaining concomitant vaccination may optimize vaccine uptake.

Microneedles enable the development of skin-targeted vaccines against coronaviruses and influenza viruses

Throughout the COVID-19 pandemic, many have seriously worried that the plus burden of seasonal influenza that might create a destructive scenario, resulting in overwhelmed healthcare capacities and onwards loss of life. Many efforts to develop a safe and efficacious vaccine to prevent infection by coronavirus and influenza, highlight the importance of vaccination to combat infectious pathogens. While vaccines are traditionally given as injections into the muscle, microneedle (MN) patches designed to precisely deliver cargos into the cutaneous microenvironment, rich in immune cells, provide a noninvasive and self-applicable vaccination approach, reducing overall costs and improving access to vaccines in places with limited supply. The current review aimed to highlight advances in research on the development of MNs-mediated cutaneous vaccine delivery. Concluding remarks and challenges on MNs-based skin immunization are also provided to contribute to the rational development of safe and effective MN-delivered vaccines against these emerging infectious diseases.

Microneedle-Mediated Vaccination: Innovation and Translation

Vaccine administration by subcutaneous or intramuscular injection is the most commonly prescribed route for inoculation, however, it is often associated with some deficiencies such as low compliance, high professionalism, and risk of infection. Therefore, the application of microneedles for vaccine delivery has gained widespread interests in the past few years due to its high compliance, minimal invasiveness, and convenience. This review focuses on recent advances in the development and application of microneedles for vaccination based on different delivery strategies, and introduces the current status of microneedle-mediated vaccination in clinical translation. The prospects for its application including opportunities and challenges are further discussed.

Toward closed-loop drug delivery: Integrating wearable technologies with transdermal drug delivery systems

The recent advancement and prevalence of wearable technologies and their ability to make digital measurements of vital signs and wellness parameters have triggered a new paradigm in the management of diseases. Drug delivery as a function of stimuli or response from wearable, closed-loop systems can offer real-time on-demand or preprogrammed drug delivery capability and offer total management of disease states. Here we review the key opportunities in this space for development of closed-loop systems, given the advent of digital wearable technologies. Particular considerations and focus are given to closed-loop systems combined with transdermal drug delivery technologies.

Lab under the Skin: Microneedle Based Wearable Devices

While the current smartwatches and cellphones can readily track mobility and vital signs, a new generation of wearable devices is rapidly developing to enable users to monitor their health parameters at the molecular level. Within this emerging class of wearables, microneedle-based transdermal sensors are in a prime position to play a key role in synergizing the significant advantages of dermal interstitial fluid (ISF) as a rich source of clinical indicators and painless skin pricking to allow the collection of real-time diagnostic information. While initial efforts of microneedle sensing focused on ISF extraction coupled with either on-chip analysis or off-chip instrumentation, the latest trend has been oriented toward assembling electrochemical biosensors on the tip of microneedles to allow direct continuous chemical measurements. In this context, significant advances have recently been made in exploiting microneedle-based devices for real-time monitoring of various metabolites, electrolytes, and therapeutics and toward the simultaneous multiplexed detection of key chemical markers; yet, there are several grand challenges that still exist. In this review, we outline current progress, recent trends, and new capabilities of microneedle-empowered sensors, along with the current unmet challenges and a future roadmap toward transforming the latest innovations in the field to commercial products.

Administration of pilocarpine by microneedle patch as a novel method for cystic fibrosis sweat testing

The sweat test is the gold standard for the diagnosis of cystic fibrosis (CF). The test utilizes iontophoresis to administer pilocarpine to the skin to induce sweating for measurement of chloride concentration in sweat. However, the sweat test procedure needs to be conducted in an accredited lab with dedicated instrumentation, and it can lead to inadequate sweat samples being collected in newborn babies and young children due to variable sweat production with pilocarpine iontophoresis. We tested the feasibility of using microneedle (MN) patches as an alternative to iontophoresis to administer pilocarpine to induce sweating. Pilocarpine-loaded MN patches were developed. Both MN patches and iontophoresis were applied on horses to induce sweating. The sweat was collected to compare the sweat volume and chloride concentration. The patches contained an array of 100 MNs measuring 600 μm long that were made of water-soluble materials encapsulating pilocarpine nitrate. When manually pressed to the skin, the MN patches delivered >0.5 mg/cm2 pilocarpine, which was double that administered by iontophoresis. When administered to horses, MN patches generated the same volume of sweat when normalized to drug dose and more sweat when normalized to skin area compared to iontophoresis using a commercial device. Moreover, both MN patches and iontophoresis generated sweat with comparable chloride concentration. These results suggest that administration of pilocarpine by MN patches may provide a simpler and more-accessible alternative to iontophoresis for performing a sweat test for the diagnosis of CF.

Optimization of Layered Dissolving Microneedle for Sustained Drug Delivery Using Heat-Melted Poly(Lactic-Co-glycolic Acid)

Dissolving microneedles (DMNs) have been used as an alternative drug delivery system to deliver therapeutics across the skin barrier in a painless manner. In this study, we propose a novel heat-melting method for the fabrication of hydrophobic poly(lactic-co-glycolic acid) (PLGA) DMNs, without the use of potentially harmful organic solvents. The drug-loaded PLGA mixture, which consisted of a middle layer of the DMN, was optimized and successfully implanted into ex vivo porcine skin. Implanted HMP-DMNs separated from the patch within 10 min, enhancing user compliance, and the encapsulated molecules were released for nearly 4 weeks thereafter. In conclusion, the geometry of HMP-DMNs was successfully optimized for safe and effective transdermal sustained drug delivery without the use of organic solvents. This study provides a strategy for the innovative utilization of PLGA as a material for transdermal drug delivery systems.

Microneedles: A New Generation Vaccine Delivery System

Transdermal vaccination route using biodegradable microneedles is a rapidly progressing field of research and applications. The fear of painful needles is one of the primary reasons most people avoid getting vaccinated. Therefore, developing an alternative pain-free method of vaccination using microneedles has been a significant research area. Microneedles comprise arrays of micron-sized needles that offer a pain-free method of delivering actives across the skin. Apart from being pain-free, microneedles provide various advantages over conventional vaccination routes such as intramuscular and subcutaneous. Microneedle vaccines induce a robust immune response as the needles ranging from 50 to 900 μm in length can efficiently deliver the vaccine to the epidermis and the dermis region, which contains many Langerhans and dendritic cells. The microneedle array looks like band-aid patches and offers the advantages of avoiding cold-chain storage and self-administration flexibility. The slow release of vaccine antigens is an important advantage of using microneedles. The vaccine antigens in the microneedles can be in solution or suspension form, encapsulated in nano or microparticles, and nucleic acid-based. The use of microneedles to deliver particle-based vaccines is gaining importance because of the combined advantages of particulate vaccine and pain-free immunization. The future of microneedle-based vaccines looks promising however, addressing some limitations such as dosing inadequacy, stability and sterility will lead to successful use of microneedles for vaccine delivery. This review illustrates the recent research in the field of microneedle-based vaccination.

Dissolvable Microneedle Patches to Enable Increased Access to Vaccines against SARS-CoV-2 and Future Pandemic Outbreaks

Vaccines are an essential component of pandemic preparedness but can be limited due to challenges in production and logistical implementation. While vaccine candidates were rapidly developed against severe acute respiratory syndrome coronavirus 2 (SARS-COV-2), immunization campaigns remain an obstacle to achieving herd immunity. Dissolvable microneedle patches are advantageous for many possible reasons: improved immunogenicity; dose-sparing effects; expected low manufacturing cost; elimination of sharps; reduction of vaccine wastage; no need for reconstitution; simplified supply chain, with reduction of cold chain supply through increased thermostability; ease of use, reducing the need for healthcare providers; and greater acceptability compared to traditional hypodermic injections. When applied to coronavirus disease 2019 (COVID-19) and future pandemic outbreaks, microneedle patches have great potential to improve vaccination globally and save many lives.

Microarray patches enable the development of skin-targeted vaccines against COVID-19

The COVID-19 pandemic is a serious threat to global health and the global economy. The ongoing race to develop a safe and efficacious vaccine to prevent infection by SARS-CoV-2, the causative agent for COVID-19, highlights the importance of vaccination to combat infectious pathogens. The highly accessible cutaneous microenvironment is an ideal target for vaccination since the skin harbors a high density of antigen-presenting cells and immune accessory cells with broad innate immune functions. Microarray patches (MAPs) are an attractive intracutaneous biocargo delivery system that enables safe, reproducible, and controlled administration of vaccine components (antigens, with or without adjuvants) to defined skin microenvironments. This review describes the structure of the SARS-CoV-2 virus and relevant antigenic targets for vaccination, summarizes key concepts of skin immunobiology in the context of prophylactic immunization, and presents an overview of MAP-mediated cutaneous vaccine delivery. Concluding remarks on MAP-based skin immunization are provided to contribute to the rational development of safe and effective MAP-delivered vaccines against emerging infectious diseases, including COVID-19.

Fabrication of microneedle patches with lyophilized influenza vaccine suspended in organic solvent

Skin vaccination by microneedle (MN) patch simplifies the immunization process to increase access to vaccines for global health. Lyophilization has been widely used to stabilize vaccines and other biologics during storage, but is generally not compatible with the MN patch manufacturing processes. In this study, our goal was to develop a method to incorporate lyophilized inactivated H1N1 influenza vaccine into MN patches during manufacturing by suspending freeze-dried vaccine in anhydrous organic solvent during the casting process. Using a casting formulation containing chloroform and polyvinylpyrrolidone, lyophilized influenza vaccine maintained activity during manufacturing and subsequent storage for 3 months at 40 °C. Influenza vaccination using these MN patches generated strong immune responses in a murine model. This manufacturing process may enable vaccines and other biologics to be stabilized by lyophilization and administered via a MN patch.