The role of pre-gravidity measles–rubella immunization of mothers on the passive immunity and immunizing effect of MMR vaccine in their offspring

Background: After national mass catch-up campaign of measles-rubella (MR) immunization on 5-25 year-old individuals in December 2003, in Iran, this research was conducted to assess the role of mothers' MR vaccination on persistence of passive immunity against measles-rubella in their infants before MMR, and the effect on the immunogenicity of MMR vaccine in these children.
Methods: From June 2005 to March 2006, all healthy 12 month-old infants presented for routine MMR vaccination were enrolled. Before and 4-8 weeks after immunization, sera samples were collected. According to their mother's history of MR vaccination, infants were divided into two-groups. Anti-measles-mumps–rubella antibodies were measured by quantitative ELISA method. The difference of seroconversion rates and mean concentration of antibodies (MCA) between the two-groups of infants were analyzed by descriptive statistical methods using SPSS 11.
Findings: Totally 112 infants (mean age 12.1 months, 58% male) from 112 paired mothers (mean age: 24.3 years, 75% MR vaccinated) were recruited. From sera taken before MMR vaccination, 7, 2 and 12 were positive against measles, mumps and rubella, respectively. All seropositive cases for measles and rubella were born to MR vaccinated mothers. Seroconversion rates were: 90.5%, 80% and 53% in infants for measles, mumps and rubella, respectively. Seroconversion rate differences between the two groups of infants for measles, mumps and rubella were not statistically significant (measles: 88.3% of vaccinated vs 96.4% of non-vaccinated, rubella: 51.4% vs 57.1%, respectively). However, anti-measles and anti-rubella MCA differences between the two groups were significant.
Conclusions: These study findings indicate that MR vaccination of mothers causes more prolongation of passive immunity persistence in their infants, and may influence the immunogenicity of MMR vaccine in infants. Also results showed that immunogenicity of rubella component of MMR vaccine was not satisfactory.

Keywords
MMR vaccine , Mother MR vaccination , Passive immunity , Immunogenicity