Duration of the immune response to MMR vaccine in children of two age-different groups.

A combined vaccine against measles, mumps and rubella (MMR) was administered to both a group of children aged 10-12 months simultaneously with booster doses of compulsory diphtheria-tetanus toxoids and oral poliovirus vaccine and a group of children aged 15-24 months who had previously received booster doses of the compulsory vaccines. Apart from one subject belonging to the second group who was non responder and one from the same group who did not seroconvert against the mumps virus alone, 5 to 6 weeks after MMR vaccine administration we found protective levels of antibodies against measles, mumps and rubella viruses in all children. The follow up of both groups at 3 years did not reveal difference between the two groups. Protective levels of serum antibodies against measles and mumps were found in the two groups, although a significant decline of rubella antibodies was shown (p < 0.05). Since the immunogenicity of the vaccines in the two groups did not differ, we recommend that the scientific community reconsider the vaccination schedule until now recommended. In our opinion the MMR vaccine should be administered simultaneously with booster doses of diphtheria-tetanus toxoids and oral poliovirus vaccine at 10-12 months of age because this policy improves parents' compliance, markedly reduces community costs and simplifies routine immunization schedule.