By Noelle Kuhn, Radnor High School, Radnor, Pennsylvania, USA
More than any other medical advancement, vaccines have arguably been the most essential to maintaining the world’s collective health since they are effective in decreasing the spread of viral illnesses on a large scale. As vaccines are created, wealthy countries such as the United States have had little trouble obtaining vaccine doses and immunizing their citizens. Many low-income countries, however, have not been as lucky. Limited access to vaccines has led to numerous outbreaks that could have been easily prevented had their citizens been properly immunized. It is estimated that measles kills over 100,000 people annually and 100,000 infants are born with rubella syndrome across developing countries, even with a measles and rubella (MR) vaccine on the market (Prausnitz et al., 2020).
Typically, most issues arise not in obtaining vaccine doses but in properly transporting and administering them to remote areas of developing countries. Many vaccines on the market, such as the measles vaccine, have strict temperature requirements for storage that are often difficult for countries with minimal resources to meet. Some vaccines administered with a needle and syringe can only be used within a few hours of being reconstituted with a diluent. Moreover, health care workers in low-resource settings are often hesitant to open vaccine vials in fear that too few people will show up to be immunized and the dose will go to waste (Peyraud et al., 2019). But a new microarray technology addresses these complications, potentially making vaccination in developing countries more feasible and efficient.
Microarray patches (MAP) are bandage-like patches with thousands of projections less than one millimeter long that can be used to deliver vaccines and other drugs through the dermis or epidermis of the skin. (Peyraud et al., 2019). Eight types of microarray patches have been developed so far, including coated MAPs, solid projections coated in a vaccine, and dissolvable MAPs, a polymer-vaccine blend that dissolves into the skin after application (Korkmaz et al., 2021).
Figure 1. Diagram of microarray patch on the skin
Because of their design, vaccines administered with a MAP do not require a diluent and are delivered ready to be administered. Additionally, MAP vaccinations do not have to be conducted solely by medical professionals, which is beneficial for countries with a limited number of health care workers. The MAP also eliminates the fear of wasting vaccine doses, as the patches are designed to administer single doses (Peyraud et al., 2019).
Although the advantages of MAPs seem convincing enough, its success wholly depends on its effectiveness in comparison to traditional vaccine methods. The first study to prove the MAP’s effectiveness was an experimental study by the Prausnitz group in 2010. Using a dissolvable MAP with the influenza vaccine on mice, the group demonstrated that the MAP successfully dissolved into the skin within minutes and produced an immune response even greater than intramuscular vaccination (Rodgers et al. 2019). New research reveals the presence of a large quantity of antigen-presenting and immune accessory cells within the skin, which is likely the reason for the increased immune response (Korkmaz et al., 2021).
Figure 2. Diagram of the protective layers of the skin and microarray patch compared to hypodermic IM vaccination needle
Compared to animal models, experimental studies on humans provide more conclusive data on the MAP’s efficacy. In a 2015 study, the effects of the influenza vaccine administered with a dissolvable MAP were observed in 40 male patients. The results demonstrated that the MAP produced equal or greater immune responses compared to the conventional injection method (Rodgers et al., 2019). One of the biggest barriers the MAP overcomes is the cold chain requirement. It is often difficult for developing countries to fund the manufacturing, transportation, and storage of a vaccine at one specific temperature. Moreover, isolated communities often have minimal access to electricity, power refrigerators and other essential storage equipment. For example, in the small Haitian village of Taillefer, Joseph Mesura, a 65 year old man, walks for six hours each month to deliver the gas needed to power the vaccine-filled refrigerator powered so local children can be immunized (“Cold Supply for Hot Demand” n.d.). MAPs, though, have the potential to eliminate this burden.
Since MAPs contain vaccines in their dried form, scientists predict that the cold chain requirement will not be necessary. Studies on the influenza vaccine have concluded that when kept at room temperature for 6 months, the MAP vaccine maintains its effectiveness and potency (Rodgers et al., 2019). A 2015 study also demonstrated the MAP’s thermostability for the measles vaccine. Compared to a liquid reconstituted measles vaccine, which lost almost all its potency in 3 weeks at 77 degrees Fahrenheit, the MAP maintained all its potency for 4 months at the same temperature. These are promising findings, especially for the measles vaccine, as countries like the Dominican Republic of the Congo are still struggling to combat large outbreaks (Edens et al., 2016).
Although the benefits of the MAP seem to outweigh the benefits of the needle-syringe vaccines, factors such as acceptability, reliability, safety, packaging, delivery, and cost must all be evaluated before MAPs can reach the places where they are needed most. Studies done in Ghana, Benin, Nepal, and Vietnam used an inactive influenza vaccine with either the coated or dissolvable MAP to test acceptability among parents, children, healthcare workers and community representatives. The study showed the MAPs were widely accepted and even preferred over needle injections. One concern that was expressed, however, was the reliability and the consistency of skin penetration. For self-administering MAPs especially, application devices or feedback systems that indicate a successful vaccination are an important factor in acceptability and widespread usage (Peyraud et al. 2019).
As the studies and logistics of the microarray patch continue to develop, we can begin to hope that low-income countries will have a fairer chance of securing vaccines to eliminate deadly viral illnesses and keep their communities safe.
References
[Diagram of the protective layers of the skin]. (2021, February 2). https://www.sciencedirect.com/science/article/pii/S0169409X2100034X#f0010
Edens, C., Collins, M. L., Goodson, J. L., Rota, P. A., & Prausnitz, M. R. (2016, September 8). A microneedle match containing measles vaccine is immunogenic in non-human primates. Retrieved April 17, 2021, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4554796/
Gavi. (n.d.). Cold supply for hot demand. Gavi: The Vaccine Alliance. Retrieved April 17, 2021, from https://www.gavi.org/vaccineswork/cold-supply-hot-demand
Korkmaz, E., Balmert, S. C., Sumpter, T. L., Carey, C. D., Erdos, G., & Falo, L. D., Jr. (2021, February 2). Microarray patches enable the development of targeted vaccines against COVID-19. Retrieved April 17, 2021, from https://www.sciencedirect.com/science/article/pii/S0169409X2100034X
[Microarray Patch]. (n.d.). PATH. https://www.path.org/programs/mdht/mapresources/
Peyraud, N., Zehrung, D., Jarrahian, C., Frivold, C., Orubu, T., & Giersing, B. (2019, July 26). Potential use of microarray patches for vaccine delivery in low- and middle- income countries. Retrieved April 17, 2021, from https://www.sciencedirect.com/science/article/pii/S0264410X19303573?via%3Dihub
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Prausnitz, M. R., Goodson, J. L., Rota, P. A., & Orenstein, W. A. (2020). A microneedle patch for measles and rubella vaccination: a game changer for achieving elimination. Current opinion in virology, 41, 68–76. https://doi.org/10.1016/j.coviro.2020.05.005
Rodgers, A. M., Cordeiro, A. S., & Donnelly, R. F. (2019, September 19). [Technology update: dissolvable microneedle patches for vaccine delivery]. Retrieved April 17, 2021, from https://www.dovepress.com/technology-update-dissolvable-microneedle-patches-for-vaccine-delivery-peer-reviewed-fulltext-article-MDER