Rubella immunity and morbidity: impact of different vaccination programs in Finland 1979-1992.

As the previous vaccination of 11- to 13-year-old girls proved ineffective, nationwide vaccination of preschool children with 2 doses of combined vaccine against measles, mumps, and rubella was started in Finland in 1982. To study the impact of vaccination, age-stratified rubella immunity and the occurrence of serologically verified rubella cases were determined using the computerized data of our diagnostic virus laboratory. The analysis covered the period 1979-1992, included all ages, and was based on the test results from 94,000 sera. By 1992, the seropositivity rate was 92-100% in 2- to 15-year-old children, remained high in females of all ages, but showed a gap in 16- to 19-year-old males. The number of verified rubella cases decreased to about 1/100, but outbreaks still occurred until 1991, when most cases were among adolescent males. The better protection of women was due to the vaccination of prepubertal girls since 1975. No congenital rubella infections were diagnosed after 1986. The 2-dose immunization of preschool children, complemented by selective vaccination of certain other groups, has resulted in excellent immunity in children and young adults, and practically eliminated rubella from the country.