A boy who received a double dose of the MMR vaccine nine months ago is having psychological tests after his family claimed he was showing signs of autism.

The boy's mother, who has requested anonymity, said that her son, who is five, was given the second dose by mistake after the family moved from Kendal, Cumbria, to another town in South Lakeland.

His new GP did not know that he had already had the vaccine. Within days of receiving the second jab on 7 January a health visitor called to say that there had been a mistake. The mother said that after the second dose her son's behaviour changed. "He has tantrums and is violent when he doesn't understand something and can't cope with groups of people," she said. "We are convinced that it is autism." The boy has been seen by a consultant who was unable to confirm whether or not the boy had autism. "He has now got to have further tests and see a psychologist," his mother said.

Dr Frank Atherton, director of public health for Morecambe Bay Primary Care Trust said that a number of children had received double doses of vaccines but there was no evidence that getting an extra dose was damaging. Despite safeguards against double doses there was always potential for error, he said. "If a child was given a vaccine at the wrong time or an extra dose of a vaccine, then that child suffers a bit of harm which was unnecessary." But he added: "There's no evidence for MMR or any vaccine that getting an extra dose leads to longer-term damage." Dr Atherton said that no diagnosis had been made in the boy's case.