Research suggested that, at least among one group of children, the chickenpox vaccine is only 40% effective, much less than previously reported.

Dr Jane Seward and colleagues from the US Centers for Disease Control and Prevention investigated a recent outbreak of chickenpox at a New Hampshire day care center. They decided that the outbreak in 23 children had begun with a child who had been vaccinated, contradicting the belief that such "breakthrough" cases are not contagious. The four-year-old child was confirmed not to have developed chickenpox infection from the vaccine they had received, but probably because the jab had not stopped them developing the illness after exposure to a sibling with shingles.

Ed.- Another, separate piece of research challenged the need for mass vaccination against chickenpox anyway.

Dr. Bernard Duval and colleagues from Laval University in Quebec (Canada) established that 92% of children had acquired natural immunity against chickenpox by the age of ten and, of those who had never had or whose parents were unsure whether their children had had the illness, two thirds had acquired natural immunity.