A change in bird flu virus strain H5N1 has diminished the effectiveness of vaccines against the disease among poultry, local newspaper Pioneer Thursday quoted a local official as saying.
Bird flu vaccines are produced according to the gene type Z found in bird flu virus strain H5N1 in 2003 when Vietnam was first hit by the disease, but another gene type called G was detected in 2005, said Nguyen Tien Dung, head of the Ultra-Virus Department of the Veterinary Institute under the Ministry of Agriculture and Rural Development.
The gene type Z and type G are not very similar, so the vaccines are more effective to the type Z, and less effective to the type G, he said, noting that first infected poultry with the type G in Vietnam were mainly smuggled.
Vietnam is strengthening bird flu vaccinations among fowls nationwide, using the vaccines imported mainly from China and the Netherlands, according to the ministry's Department of Animal Health.
Bird flu, starting to strike Vietnam in December 2003, has since early this month hit 12 Vietnamese cities and provinces, namely Quang Ninh, Son La, Nam Dinh, Hai Phong, Bac Giang, Ninh Binh, Bac Ninh, Ha Nam and Vinh Phuc in the northern region, Nghe An in the central region, and Can Tho and Dong Thap in the southern one.