Vaccines usually consist of inactivated viruses that prompt the immune system to launch a strong defense if it encounters an active virus. But, for certain viruses, like HIV, even this is taking too much of a chance.

In recent years, scientists have been exploring DNA as a potential alternative vaccine. Researchers at Massachusetts Institute of Technology (MIT), Cambridge, are experimenting with a new type of vaccine-delivery film that could improve the effectiveness of DNA vaccines.

If such vaccines could be successfully delivered in humans, they could overcome not only the safety risks of using viruses to vaccinate against diseases such as HIV, but they would also be more stable, making it possible to ship and store them at room temperature.

This vaccine delivery system would also eliminate the need to use syringes. Providers would apply a patch for a few minutes, then remove it and it leaves behind thin polymer films embedded in the skin.

They created a multi-layered patch made of polymers embedded with a DNA vaccine. The polymer films are implanted under the skin using microneedles that penetrate about half a millimeter into the skin—deep enough to deliver the DNA to immune cells in the epidermis, but not deep enough to cause pain in the nerve endings of the dermis.

Once under the skin, the films degrade as they come in contact with water, releasing the vaccine over days or weeks, which allows the immune system time to interact with it, and boosting the vaccine’s effectiveness. As the film breaks apart, the DNA strands become tangled up with pieces of the polymer, which protect the DNA and help it get inside cells.

The researchers now plan to perform further tests in non-human primates before undertaking possible tests in humans. If successful, the vaccine-delivering patch could potentially be used to deliver vaccines for many different diseases, because the DNA sequence can be easily swapped out depending on the disease being targeted.

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