Vaccination against influenza started in October. This year's vaccine targets three types of flu: H1N1 influenza, which broke out last year, and the A/Hong Kong-type and B-type influenza. In the last flu season, the damage from H1N1 influenza was not as serious as had been feared, probably because its pathogenicity was rather weak.

At this stage, it is not known whether the pathogenicity will strengthen, and whether the new type of influenza will become more rampant than in the last flu season. One cannot be too cautious and people are strongly advised to be vaccinated as soon as possible. After inoculation, it takes about two weeks for the vaccine to become effective.

This year, mass outbreaks of influenza have already been reported. At a hospital in Kita Akita, Akita Prefecture, 66 in-patients and 20 hospital workers came down with the A/Hong Kong-type influenza on and after Oct. 27 and eight people died between Oct. 31 and Nov. 5, their ages ranging from the 60s to the 90s. All the in-patients had been vaccinated. It is believed that the influenza broke out before the vaccine became effective. This reinforces the case for receiving the vaccine at an early date.