Determination of meningococcal antibodies by microassay

A modified microassay procedure, using triphenyltetrazolium chloride as a germination indicator, was compared with a macroassay method proposed by the World Health Organization for determining the level of antibodies before and after immunization with Group A meningococcal polysaccharide vaccine. There was excellent agreement between the results obtained by the two methods. The vaccine used appeared to be safe and immunogenic.