Immunisation Division, Communicable Disease Surveillance Centre, Public Health Laboratory Service, 61 Colindale Avenue, London NW9 5EQ, UK. emiller@phls.org.uk
Combined measles, mumps, and rubella (MMR) vaccine did not increase the risk of hospitalisation with invasive bacterial infection in the three months after vaccination; rather there was a protective effect. These results provide no support for the concept of "immunological overload" induced by multiple antigen vaccinations, nor calls for single antigen vaccines.