IMMUNITY TO RUBELLA BEFORE AND AFTER VACCINATION AGAINST MEASLES, MUMPS AND RUBELLA (MMR) AT 12 YEARS OF AGE OF THE FIRST GENERATION OFFERED MMR VACCINATION IN SWEDEN AT 18 MONTHS

In 1982, a two-dose programme of vaccination against measles, mumps an d rubella (MMR) at the ages of 18 months and 12 years was introduced i n Sweden. In 1992-3, the first group of children vaccinated at 18 mont hs reached the age of 12, i.e. the time for a second dose. In connecti on with this 12-year vaccination, 376 children were recruited investig ated concerning earlier MMR vaccination and bled prior to and 2 months after the immunization. Two hundred and twenty of them had a document ed earlier MMR vaccination and 156 had not. The latter were classified as unvaccinated The antibody status against rubella was measured by t he haemolysis-in-gel method. Prior to the present vaccination, 3% of t he earlier vaccinated group totally lacked any sign of antibodies. In the presumably unvaccinated group, this figure was 76%. After the vacc ination all children showed signs of antibody acitivity and all reache d the antibody level of greater than or equal to 15 international unit s, i.e. in our rests a zone dia. of approx 8 mm. However, the secondly vaccinated children ended lip with a mean antibody level of 10.7 mm w hich was slightly lower than the level, i.e. 11.0 mm of those lacking earlier vaccination history and prevaccination seronegative. The earli er unvaccinated bur pre-immune children reached a mean level of 11.2 m m. In general, those with relatively high, pre-vaccination, antibody l evels reacted less to the booster than chose with low or no pre-vaccin ation immunity. The booster thus appeared to restore the antibody leve ls of the low-titre children.