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.

Since the strain of H1N1 influenza has a common feature with the strain of the A/Soviet-type influenza, which has hit Japan in the past, many adults have basic immunity and have been spared serious symptoms. Serious cases were found in the last season among children who had no basic immunity against the new flu and adults who had life style-related illnesses. Fortunately, no pregnant women, who were feared to be vulnerable to the virus, died from the H1N1 influenza.

World Health Organization Director General Margaret Chan said Japan has had the lowest death rate among sufferers of the new flu, adding that the country responded quickly and offered people good access to hospitals and clinics. People can take preventive steps, such as washing their hands frequently, avoiding crowded places and wearing masks. These easy steps may have helped prevent a worse outbreak of influenza last year.