Nobody likes getting needles, plus the things pose a biohazard when discarded, and the liquid medication that they deliver needs to be refrigerated. A new flu vaccine skin patch, however, has none of those drawbacks – and recent mouse trials have shown it to be effective at boosting immunity against the virus.
First of all, there are already patches that deliver vaccines through the skin, via an array of microneedles on their underside. Packed with a dried form of a vaccine, those needles painlessly pierce the top layer of the skin, then release the medication into the bloodstream by harmlessly dissolving.
According to scientists at the University of Rochester Medical Center, however, those microneedle arrays can be challenging to manufacture on a commercial scale. With that in mind, researchers Lisa A. Beck, Benjamin L. Miller and Matthew Brewer have developed a patch that still delivers the vaccine, but without the use of tiny needles. Instead, it utilizes a mechanism that was inspired by the skin disease eczema.
Also known as atopic dermatitis, eczema occurs when the lack of a protein known as claudin-1 causes the skin to become overly permeable, allowing allergens such as pollen and moulds to get through. The scientists figured that by temporarily inducing that sort of permeability, flu vaccine from the underside of the patch would likewise be able to dissipate through the skin.
In order to make this happen, they mixed the vaccine with a synthetic peptide that was known to bind with and inhibit claudin-1. As a result, the skin barrier opens up when the patch is applied – letting the vaccine in – but then closes back up as soon as the patch is removed. The patch itself blocks allergens from entering while the skin is still extra-permeable.
In lab tests, prototype patches were placed on the backs of mice for several hours a day, over a period of three months. No skin problems or other side effects occurred, and in cases where the animals had previously received a flu shot to initially prime the immune system, the vaccine which was subsequently delivered by the patch did indeed produce a strong anti-flu immune response.
There wasn't much of a response, however, when the patch was applied to mice that had not already received an injection. This suggests that while the patches could be very useful for reinforcing immunity to influenza – like the yearly flu shots that many people get – they might not be effective on infants that hadn't already received an injection or otherwise been exposed to the virus.
Once the technology has been developed further and clinically tested on humans, the researchers hope that it could be used to deliver a variety of vaccines in settings such as developing nations. There, clinicians with minimal training could administer the patches to locals who wouldn't be put off by the pain or invasive nature of hypodermic needles. Additionally, the patches wouldn't need to be kept in cold storage (if dried forms of the vaccines were used), plus they wouldn't pose a poking hazard once disposed of.
A paper on the research was recently published in the Journal of Investigative Dermatology.
