Combining vaccinations increases risk for fever-related seizures in toddlers.  The measles, mumps and rubella (MMR) and chicken pox vaccines often are administered in a four-in-one combination shot called ProQuad.  Recent finding: Children ages one to two who receive the ProQuad shot are twice as likely to suffer seizures within seven to ten days after the injection than children who receive separate MMR and chicken pox vaccines. 

Nicola Klein, MD, PhD, codirector, Kaiser Permanente Vaccine Study Center, Oakland, California, and author of a study of 459,461 children, published in Pediatrics.