A four-month-old boy died after being found unconscious at home in Sha Tin yesterday. The death of the infant, surnamed Tse, came less than 24 hours after he was vaccinated in a government health centre on Monday. But a doctor said it was 'highly unlikely' that the death was caused by the vaccine. Initial investigation showed that he suffered fever and was then fed with medicine at night, according to police. The baby had earlier received a DTaP-IPV vaccine, which is part of the childhood immunisation programme established in Hong Kong. Yesterday, his 24-year-old mother, surnamed Lee, found the infant unconscious in bed in the family's flat in Mei Lok House, Mei Tin Estate and called police at 5.23am. The baby was taken to Prince of Wales Hospital, where doctors declared him dead. Police said there were no signs of suspicious circumstances. A postmortem examination will be carried out. The boy was born in Hong Kong. His mother came from the mainland several years ago. His father is a mainland visitor. Paediatrician Alvin Chan Yee-shing said there was a one in 1,000 chance for a baby to die suddenly, but it was very rare that it was caused by vaccines. He said babies normally received injections once every month. Chan said it was more likely that the baby died of suffocation during sleep. He reminded parents that they should not let their babies lie on their stomach or sleep with adults. 'When an adult turns in the bed at night, he might bear down on the baby, who is too young to scream for help.' Chan also advised parents to make sure that the blanket was not very close to the face of the baby to minimise the chance of suffocation.