Skin patch gives bird flu vaccine a big boost

Mar 21 2008

Researchers testing an experimental skin patch designed to boost an H5N1 vaccine say preliminary results have been promising.

They say the 'adjuvant patch' which is designed to be used with an injected vaccine, could help stretch vaccine supply during a pandemic.

It seems the skin patch boosted the bird flu vaccine to such an extent that people appeared to be protected by a single dose; current approved vaccines against the H5N1 avian influenza virus need two doses to be fully effective.

The researchers at biotechnology firm Iomai, based in Maryland in the U.S., tested the patch on 500 volunteers in a phase 1/2 trial which looked at the safety and efficacy of the patch.

The patch is applied after gently scraping the skin with a light, sandpaper-like device, and is being used to boost an H5N1 vaccine made by the Belgian drug company Solvay.

The researchers say when the patch was used with a single dose of the 45-microgram H5N1 vaccine, 73 percent of those tested had what is considered a protective immune response while 49 percent of those who got the vaccine alone, without a patch, had an immune response considered protective after the first dose.

The researchers say the prospect of being able to immunize during a pandemic, with a single dose, is very attractive and they are thrilled with the results.

A one-dose vaccine-patch regimen would eliminate the need in a pandemic of every person needing a booster dose several weeks after the first or priming dose was given.

The news comes at an opportune time when bird flu continues to sweep across Asia decimating flocks of poultry.

To date the virus has infected 373 people in 14 countries and killed 236 of them since 2003 and the ongoing concern is that will eventually mutate into a strain which is transferred between people, triggering a pandemic.

At present the virus remains one of birds which is contracted by handling infected birds or poultry.

Many companies are currently testing H5N1 vaccines but no one knows precisely what a pandemic strain of the virus will be like or how to formulate the best vaccine and scientists believe people need bigger doses than with seasonal influenza.

Production capabilities are limited globally and if bigger doses are needed, that means fewer people could be vaccinated in a pandemic, which is where adjuvants come in.

Adjuvants are often used to boost vaccines and some of the experimental H5N1 vaccines include adjuvants in the formulation; they can double the number of people who could be protected with a set amount of vaccine.

Experts however are cautious about the possibility of a one-dose vaccine regime based on these findings and are more interested in the fact that an adjuvant that doesn't come pre-mixed with the vaccine was effective at boosting the response.

They say this is a huge advantage, because in theory it means that the patch can be used with any vaccine which makes an extremely valuable tool for pandemic planning.

Iomai received a $128 million grant from the National Institutes of Health to test the patch.