Vaccination against meningococcal group A disease in Finland 1974-75.

Meningococcal group A polysaccharide vaccine was used in children 3 months to 5 years of age in the winter 1974-75 during an epidemic caused by sulphanamide-resistant group A meningococci. In 3 provinces, the vaccine was offered on a double-blind basis, using Haemophilus influenzae type b polysaccaride vaccine as control. Approximately 100 000 children were vaccinated with either one of the vaccines. In the Kymi province, approximately 22 000 children representing 90% of the child population of this age received the meningococcus vacine. Infants below 18 months received a booster dose of vaccine 3 months after the first dose. The meningococcus vaccine caused local symptoms in 71%, mild systemic reactions in 37%, and high fever (38.5 degrees C or more) in 1.8% The haemophilus vaccine produced fewer side effects. No clinical infections caused by group A meningococci were reported in the first 6 months after vaccination among those who had received the meningococcal vaccine. At the same time, group A cases continued to appear in other age groups and other areas of the country.