19 February 2010
In a semiannual update on avian influenza activity, the World Health Organization (WHO) has recommended that health authorities begin developing a candidate vaccine virus for the most recently recovered isolates of avian influenza strain H9N2. That subtype, which is endemic in poultry in parts of Asia and the Middle East, caused two unrelated human infections in Hong Kong in late 2009. The patients, who were mildly ill and recovered, were a 47-year-old woman and a 35-month-old child who were not related; both had traveled to mainland China. Isolates from the patients were not completely reactive to ferret antiserum to the existing H9N2 candidate vaccine virus, which was isolated in 1999. That existing vaccine and one made from a 1997 isolate have been studied in eight clinical trials testing different formulations and dosages. Three were conducted by the US National Institute of Allergy and Infectious Diseases, including one using an adjuvanted vaccine purchased from Novartis Vaccines and Diagnostics, formerly Chiron Corp., that returned good results in 2006. The WHO also reported that strains of H5N1 avian flu belonging to at least five different viral clades have caused poultry outbreaks since September 2009, but the agency did not recommend that any additional H5N1 candidate vaccine viruses be developed.
A review on the influenza A(H5N1) and A(H9N2) virus activity and virus characterization can be found in the attached link.