COVID-19 Vaccine Patch

Online Science Editor Daisy Scott discusses the recent development of a COVID-19 vaccine in the form of a patch.

Researchers from Carolina and Stanford Universities have developed a microneedle vaccine patch that outperforms needle jabs to boost immunity. This article will discuss how this patch will work and what the benefits of this type of vaccine is over traditional vaccinations.

As of 11 August 2021, SARS-CoV-2 has caused more than 202 million infections resulting in more than 4.2 million deaths. 49 per cent of the global population have received at least one dose of the COVID-19 vaccine globally, however, only 5 out of 54 African nations are projected to hit the World Heath Organisations year-end goal of fully vaccinating at least 40 per cent of their residents. The main barriers to increasing vaccinations in lesser developed countries is lack of access to the cold storage that is required for the storage of the currently most used vaccines and also the medical staff that are required to administer them.

SARS-CoV-2 has caused more than 202 million infections resulting in more than 4.2 million deaths

The patch is a centimetre-wide skin patch that is covered with 5,000 tiny plastic spikes, each of which are a quarter of a millimetre long and coated with a dried vaccine (HEXAPRO) which will dissolve into the skin. The vaccines used in the patch are a “subunit” vaccine that reproduces the spike proteins that cover the surface of the coronavirus and was made by using a nitrogen jet-based drying process to turn a stabilised version of the coronavirus spike protein into powder. The patch is administered with the click of a small, round applicator device to the upper arm. The needles on the patch are so small that they do not draw blood or even trigger the nerve endings that cause the pain traditionally associated with vaccines. It works by delivering the spike protein to the epidermis. This top layer of the skin contains the vast network of specialised immune cells that act as sentinels, sending signals to other cells of the body when they encounter an invading pathogen.

The skin patch has a plethora of benefits over the traditional vaccines which include:

• It can be stored at room temperatures. This is in stark contrast to the most common administered vaccines which are Pfizer and AstraZeneca. The AstraZeneca vaccine is the easiest to transport as it can be transported and stored at fridge temperatures whilst the Pfizer vaccine needs to be stored at -70°c. These storage temperatures make it much more difficult to deliver the vaccines to lesser developed countries as they do not always have access to sufficient cold storage facilities. The vaccine currently used in the patch is Hexapro which has been found to be stable at room temperatures for at least a month and a week at 40° which means that it could be delivered to any part of the world. David Muller at the University of Queensland in Brisbane stated “We wanted to come up with an alternative that would be stable long enough to go that last mile, especially in resource-limited settings”.
• It does not require a doctor to administer the vaccine and therefore there is the possibly that people could administer the vaccines themselves in their own homes.
• The skin patch provides greater immune protection according to mouse studies. The mice injected with the patch in the study developed 50 times more antibodies than subcutaneous injection and were completely protected from getting sick.

The mice injected with the patch in the study developed 50 times more antibodies than subcutaneous injection

The main challenge with this vaccine now is production, with no manufacturers yet having the capacity to make enough patches en masse.

The only infectious disease ever to have been eradicated, smallpox, was done so with a skin vaccine by puncturing the skin with a 2-pronged needle that had been dipped in the vaccine solution. There are also a wide variety of drugs that are currently available in patch form, including nicotine and the contraceptive pill.

In the future, Muller envisions that patch vaccines could eventually be sent through the post or delivered by drones in harder-to-access locations. Despite these advances, skin patch vaccines aren’t likely to be widely available for another few years as the patch is only currently being studied in mice and would need further studies to be carried out in humans before it could be approved for wider use.