Under the skin of intradermal vaccines

Abstract

Needleless vaccines may immunize patients more efficiently and effectively than injections. But are these new technologies ready for prime time? At a makeshift clinic in southern Cambodia, with cows lazing on the dirt outside, children take turns sitting in a blue plastic chair, bracing themselves for the sharp pain of a measles vaccine injection. However, time and time again, the children barely flinch, let alone cry. Throughout the morning, more than 200 children are vaccinated. The key to the efficient and tearless vaccination: no needles necessary. A patch containing 36 dissolving microneedles is shown on a fingertip. The microneedles dissolve within minutes after insertion into skin to release encapsulated drug or vaccine. Each microneedle is 900-μm tall. (Image courtesy of Jeong-Woo Lee, Laboratory for Drug Delivery, Georgia Institute of Technology.) In this scene captured on video during a Cambodian measles vaccination program, a device called a jet injector shoots a high-speed jet of the drug into the skin. Unlike a typical needle syringe that sticks all of the way into muscle, this device never punctures the skin. The jet injector is just one of a number of technologies being developed to deliver vaccines to patients without using painful muscle-piercing needles: everything from patches with tens of thousands of microscopic needles that painlessly perforate the skin, to ultrasound pulses that temporarily “open” the skin for drug delivery, to special concoctions of drugs engineered to seep into the skin. A lack of pain isn’t the only advantage of such methods. Vaccines delivered using these technologies may be more effective than intramuscular injections and thus require less of the drug. Moreover, many of these technologies are easier to use in the developing world because they use vaccine formulations that don’t require refrigeration and can be administered with minimal training. The challenge is to …