Editor,—The paediatric intensive care unit at St Mary's Hospital in London admits more than 100 cases of meningococcal disease each year from over 50 different hospitals in the south east of England. Since 1992, the unit has treated over 650 patients with the disease,1 but had not treated a single case of serogroup W135 meningococcal infection until April 2000. We would like to report four children treated at our hospital for meningococcal infection due to serogroup W135, type 2A, subtype P1.2, P1.5, within a one month period from April 2000. They had been vaccinated recently with meningococcal serogroup C conjugated vaccine, and had …