May 23, 2006

Scientists discover combined vaccines more effective against bird flu

Bird flu vaccines can now be combined with a second vaccine to provide a cheap and easy way of vaccination, researchers said Monday (May 22).

Two separate teams of researchers came up with a combination that is easy to make, protects chickens well and could be administered by spraying.

The vaccines are also designed so that the virus could not be masked, reducing the risk that chickens would be passive carriers of the virus, a concern that has led to some countries banning vaccinated chickens. Normally, it is impossible to tell if a chicken has antibodies against bird flu because it was vaccinated or because it was infected. A vaccine works by introducing harmless versions of the virus into the body so that it would produce the antibodies to fight the disease.

The new vaccine is combined with vaccines for Newcastle disease, another poultry disease, so it is strictly for chickens only, said Dr Peter Palese of the Mount Sinai School of Medicine in New York.

As many companies already manufacture vaccines for the Newcastle disease, producing and administering the combined vaccine would not pose much of a problem.

Researchers grafted a piece of the H7N7 virus onto the Newcastle virus used in a commercial vaccine and found that it protected 90 percent of the chickens, they said.

Angela Roemer-Oberdoerfer and colleagues at the Friedrich Loeffler Institut at the Federal Research Institute for Animal Health in Riems, Germany made a similar vaccine using H5N1.

This vaccine can easily be detected in a blood test, thus clearing up the confusion over whether a chicken has been infected or vaccinated. The vaccine also did not allow the birds to transmit, the virus, Roemer-Oberdoerfer's team reported.