Group A meningococcal polysaccharide vaccine and course of the group A meningococcal epidemic in Finland.

A group A meningococcal epidemic started in Finland in 1973 and had its peak in 1974. Its rapid decline and end after large scale vaccinations in 1975-76, involving approximately one quarter of the population, is described. It gives further proof of the clinical efficacy of the group A polysaccharide vaccine. No corresponding increase in the other serogroups has been seen in the 1 1/2 years elapsed after these vaccinations.