Meningococcus group A vaccine in children three months to five years of age. Adverse reactions and immunogenicity related to endotoxin content and molecular weight of the polysaccharide.

Vaccination of 21,007 children between the ages of three months and five years was completed with five different lots of the meningococcal group A capsular polysaccharide vaccine. A correlation was found between the frequency and severity of adverse reactions and the endotoxin content of the vaccine lots. All vaccine lots elicited a serum antibody response. The endotoxin content of the vaccines did not correlate with the serum antibody response.