Abstract
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 1½ years elapsed after these vaccinations.