We performed field trials in the course of an epidemic in Finland to learn whether Group A memingococcal capsular polysaccharide vaccine protects infants and young children from meningitis. The first trial involved 130,178 children between the ages of three months and five years; 49,295 children received the vaccine, 48,977 received a control Haemophilus influenzae Type b polysaccharide vaccine, and 31.906 remained unvaccinated. No cases of meningitis or sepsis caused by Group A meningococci were seen in the first year of observation among the children vaccinated with meningococcal vaccine whereas six occurred among those vaccinated with the H. influenzae vaccine and 13 among those not vaccinated. In the second trial 21,007 children of the same ages received the meningococcal vaccine. No cases caused by Group A occurred among those vaccinated, although five to seven would have been expected within the year. Meningococcal Group A vaccine appears efficacious in young infants and children.

Yersinia agglutinins and—when suitable samples were available—also cultural and histological evidence of Yersinia infections have been searched for from 400 hospital patients during the period 1965–70 at Lappeenranta, Finland. In 31 of them immune responses compatible with infections caused by Yersinia pseudotuberculosis (YP) serotypes I, II, III or V or Yersinia enterocolitica (YE) serotypes 3 or 9 were found. In seven patients the diagnosis was confirmed by cultural or histological findings. YE serotype 9 was involved in 20 cases. Of the 31 patients 19 had disease states commonly regarded as immunological late effects of bacterial infections. Such states included erythema nodosum, temporary arthritides or arthralgias and also pulmonary changes resembling sarcoidosis. The joint symptoms met in children were indistinguishable from so‐called benign aseptic arthritis. One patient had a typical Löfgren's syndrome.

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