A 58-year-old man is seriously ill in hospital after being vaccinated against swine flu. News of his condition - he suffered weakness in both legs soon after receiving the jab - came as the government reported only 5 per cent of the two million people in Hong Kong deemed at high risk had taken advantage of subsidised flu shots in the three weeks they have been available. The man is the first person in the city to fall seriously ill after being vaccinated. The Centre for Health Protection is investigating his case. An expert group formed to consider serious reactions among people receving the swine flu vaccine will meet today to discuss the man's condition. Infectious-diseases specialist Dr Lo Wing-lok said it was probable that the condition was a reaction to the vaccine but the government needed to establish whether or not that was the case. One of the most serious side effects of vaccination for flu is Guillain-Barre syndrome, an acute disorder in which the body damages its own nerve cells, resulting in muscle weakness in, and sometimes paralysis of, the limbs. However, Lo said weakness in the legs was not typical of the syndrome, which more usually affected the arms, respiratory system, eyes and throat. University of Hong Kong microbiologist Dr Ho Pak-leung said the man's limb weakness would not be linked with the flu shot if the problem arose two or three days after receiving it. But if the problem arose within two or three weeks of vaccination, an investigation was needed. The man was vaccinated on Christmas Eve and admitted to Queen Mary Hospital in Pok Fu Lam on Saturday, a week after he began experiencing weakness in his legs. Ho said global statistics showed the number of cases of Guillain-Barre syndrome in people receiving flu shots was almost the same as in non-recipients. Locally, doctors saw 50 to 60 cases of the syndrome a year, he said. Lo said viral or bacterial infections of the nervous symptom, or an allergic reaction, could also be the cause of the man's condition. He said the ratio seen in Hong Kong of one serious adverse reaction per 100,000 people vaccinated was high, but urged the public to stay calm and encouraged people with chronic diseases to get vaccinated against swine flu. Just one in 20 of the people in high-risk groups have received swine flu vaccinations since they were made available on December 21, and private doctors have ordered only 63 per cent of the 100,000 shots reserved for them and have used fewer than 18,000, the Department of Health said. The government ordered three million doses of the French-made vaccine, of which 250,000 arrived last month. The remainder will arrive next week. Chinese University respiratory medicine professor David Hui Shu-cheong said the government had done its best to promote the programme. 'It is a citizen's responsibility to take the shots,' he said. The population as a whole could only be protected against swine flu if at least 70 per cent had immunity. Meanwhile, a bedridden 85-year-old woman died of swine flu in Tuen Mun Hospital - the 55th person to succumb to the virus in the city.