Flu jab with last year's vaccine may not do the job

NEW YORK (Reuters Health) - There seems to be a reduced immune response to influenza virus in adults who receive the identical flu vaccine in consecutive years, Japanese researchers warn.

"Our findings provide grounds for the reconsideration of influenza vaccination strategy, in case the vaccine strains are completely identical in consecutive years," lead investigator Dr. Shigeki Nabeshima told Reuters Health.

Nabeshima, of Kyushu University, Fukuoka, and colleagues came to this conclusion after studying 37 hospital workers who had received identical flu vaccines in 2002 and 2003.

Two weeks and 4 weeks after the vaccine was given in 2003, the immune response to the influenza strains were significantly lower in subjects who had received the same vaccine the previous year than in subjects who had never received that particular vaccine.

Six of the repeat-vaccination subjects had a third identical influenza vaccination in 2004. They also received hepatitis B vaccination as a control.

Again, the influenza immune response was depressed, but there was a normal response to the hepatitis B vaccination, showing that the weak reaction was influenza-specific, the researchers report.

Given these findings, Nabeshima says "further immunological investigation of influenza vaccination is certainly needed."

SOURCE: Journal of Medical Virology March 2007.