Could Skin Patches Be the Future of Covid Vaccines?

An estimated 49 percent of people have had at least one dose, and billions more are still waiting.
According to an October 28 statement, only five of the 54 African nations are expected to reach the World Health Organization's goal of fully vaccination at least 40% of their population by year's end. Access to cold storage refrigeration is not available and there are still major obstacles.

Researchers are currently working on Covid-19 vaccines that can be stored at room temperature and administered without the use of a needle or syringe. In Scientific Advances, the latest research is published today.

The University of Queensland, Australia, has created a skin patch vaccine against Covid-19. It can be applied with a click of a small round applicator device to your upper arm. The plastic patch measures 7 by 7 millimeters in size, smaller than a fingernail. It has 5,000 needle-like projections that penetrate the skin and deposit vaccine into the upper layers of the skin. These needles are much smaller than a normal needle and don't draw blood. This technology, also known as a microneedle pad, is used to deliver insulin and other drugs. The latest version, which is designed to protect against Covid-19 has been only tested in mice.

Scientists made the vaccine using a nitrogen jet drying process to dry a stabilized coronavirus spike protein and turn it into powder. The powdered spike protein was then applied to the patches. The vaccine patch was stable up to one month at room temperature, and for up to seven days at 40 degrees Celsius (or around 104 Fahrenheit) in laboratory tests. The patch produced more neutralizing antibodies against SARS Cov-2 in mice than vaccines given by needle and syringe.

David Muller, a senior research fellow at The University of Queensland and author of the paper, said that "we got fantastic responses".

The vaccine patch delivers the spike protein to your epidermis. The epidermis is a thick layer of skin that contains many immune cells. These immune cells provide protection against viruses and bacteria. These cells are like sentinels for the body and send signals to other cells when they come across an invading pathogen.

Mark Prausnitz, the director of the Center for Drug Design, Development and Delivery (Georgia Tech), said that the skin was a good place to administer a vaccine. He wasn't part of the new study. "Our skin is the interface between the body and the outside world. It expects to encounter pathogens every now and again and understands the necessity to mount immune responses."

Studies in animals have shown that skin patches for other diseases generate more antibodies than injections into the muscles. Prausnitz points out that smallpox was the only infective disease that has been eradicated. Smallpox was administered by using a two-pronged needle, which had been dipped into the vaccine solution.

Although the University of Queensland vaccine does not use a needle in traditional terms, it does feel a little bit like a needle when it is pressed against skin. Muller describes the applicator as a "solid flick" on the arm. He explains that you need to remove the foil seal and place it on the arm. After 10 seconds, remove the applicator.

The patch, like any vaccine, may cause some discomfort in your arm because it contains an agent that stimulates an immune response. You may also notice some redness, but this usually disappears in a few days.

Jason McClellan (a structural biologist at The University of Texas at Austin) says that it looks very promising. He helped to design the coronavirus spike proteins used by the Queensland researchers in their vaccine formulation, but was not involved in the study.

McClellan believes that a vaccine that does not require cold storage will be a boon for less-affluent nations, which have limited access to electricity. He says that this is a significant advantage over the Covid-19 mRNA vaccines which require low temperatures. It is not easy to keep a cold chain in many places around the globe.

Muller imagines that one day, patch vaccines will be delivered via the mail or drones to hard-to reach places with no cold storage. This would allow individuals to self-administrate them.

Others are developing shelf-stable vaccine products that do not require an applicator. They would stick to the skin like a band-aid and then disappear. They would be almost as painless as the University of Queensland's solid patch. Researchers from Carnegie Mellon University and the University of Pittsburgh have created a patch the size of a fingertip. It contains 400 tiny sugar and protein needles that dissolve in the skin after the spike protein is delivered. The vaccine created antibodies in mice by the Pittsburgh team that were high enough to neutralize coronavirus.

Researchers from Stanford University and University of North Carolina at Chapel Hill are working together to create a 3-D-printed skin patch for Covid-19. The mice responded 50 times better to the small, dissolvable patches than when they were injected with vaccine under their skin.

For decades, skin patches have been used to deliver drugs. Many drugs, including nicotine and contraceptive pills, are now available as patches. Researchers have been more interested in developing vaccines that can be delivered via this method of delivery in recent years.

Skin patch vaccines may not only be beneficial in poorer settings but they could also encourage vaccination in other areas. Prausnitz believes that more people would receive the flu vaccine if it were less painful and was easier to access. He says that there is a strong motivation to make the flu vaccine more accessible. "What if you could grab your patches from the grocery store on the way home and take them home to your loved ones?"

A skin patch may be an option for adults and children who are afraid of needles. Gavi, The Vaccine Alliance published a study in May that found that around 10% of people who have not received a Covid-19 vaccination fear needles.

For the next few years, it is unlikely that skin patches for flu or Covid-19 will be widely available. None of the Covid-19 patch vaccines have been tested on humans. The University of Queensland team plans to start a clinical trial next year together with Vaxxas, a biotech company based in Cambridge, Massachusetts that manufactures the patches and applicators.

Although skin patches for Covid-19 are still a ways off, Prausnitz believes it's still worth investing in them. Experts predict that coronavirus will spread rapidly and that booster vaccines may be required. A simple-to-use, stable vaccine option could be a way to ensure that the majority of the world's population gets vaccinated.