Effect of infant immunisation with meningococcus serogroup C-CRM(197) conjugate vaccine on diphtheria immunity and reactogenicity in pre-school aged children.

The majority of Men C conjugate vaccines given in the UK use CRM(197), a mutant diphtheria toxoid, as their protein carrier. We studied the effects of prior immunisation with Men C-CRM(197) conjugate vaccine on immunity to diphtheria in 193 children before and after a booster dose of Men C at 4 years. Baseline diphtheria antibodies were higher in children given four previous doses of Men C (P<0.0001) and tended to be higher following boosting in those who had received three or four doses. This enhanced immunity was not associated with increased reactogenicity.