29 July 2010

Researchers Find Way to take the 'Shot' out of the Flu Shot

LA Times

The microneedles on this flu patch are shorter than the width of a nickel. (Georgia Tech, Sean P. Sullivan / July 19, 2010)
There are so many things wrong with flu shots. For starters, they usually involve needles. The alternative, spraying vaccine up into the nose, isn't exactly comfortable either.

There are logistical problems too. Flu vaccine has to be kept refrigerated or else it will go bad. The shots and sprays must be administered by a doctor or nurse, which typically necessitates a trip to a medical office. Then there is the problem of disposing of so many syringes and spray tubes.

If only there were a way for people give themselves the flu vaccine. It would have to be simple — as easy as applying a Band-Aid. It would have to be painless. It would have to work at room temperature and be available at the corner drugstore. And, as long as we're dreaming up this wish list, why not insist that it not produce any biohazardous waste?

Well, dear reader, you'll be happy to hear that the good folks at Georgia Tech and Emory University are a few steps ahead of you.

These researchers have invented a microneedle patch that can deliver flu vaccine painlessly to the skin. Here's how they describe it in a paper published online Sunday in the journal Nature Medicine:

"Microneedles are micron-scale structures that painlessly pierce into the skin to administer vaccines in a minimally invasive and targeted manner."

Each microneedle is 650 microns long, about as tall as 10 human hairs stacked on top of each other. (In the picture accompanying this post, you can see that the needles are significantly shorter than a nickel laid on its side.) They are arrayed in a grid-like pattern on a patch that's easy to stick on your arm. The researchers experimented with one by pressing it onto the skin of a pig cadaver and found that nearly 90% of the microneedles dissolved within five minutes.

It turns out the skin is a great place to inject vaccine. As it forms a natural barrier between your internal organs and the outside world, it is fairly brimming with cells that are on the lookout for foreign invaders and stand ready to initiate an immune response when any are detected. Some studies have found that flu vaccine can be given in lower doses if injected into the skin instead of the muscle (which is where needles deliver their payload).

The researchers put their flu patch to the test by giving it to mice and comparng them to other mice who got their vaccine in an old-fashioned needle. Both groups of mice made flu antibodies and were able to withstand a flu challenge 30 days after vaccination. None of the unvaccinated mice survived beyond six days.

Two months later, the researchers infected both groups of immunized mice again. The ones who got the flu patch were 1,000 times more efficient at clearing the virus from their lungs than the ones who got the flu shot.

"Overall, these results show that dissolving microneedle patches offer an attractive approach to administer influenza vaccine with improved safety, immunogenicity and logistical operations that may enable an increased population coverage for influenza vaccination," the researchers concluded. Moreover, their patch "also provides a new platform technology for simple administration of other vaccines and medicines to skin without the need for hypodermic needles."

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