Impact of Vaccination on Maternal Antibody Levels
ABSTRACT & COMMENTARY
By Hal B. Jenson, MD, FAAP, Dean, Western Michigan University School of Medicine, Kalamazoo, MI. Dr. Jenson reports no financial relationships in this field of study.
SYNOPSIS: As MMR vaccination coverage among mothers increases, compared to mothers with natural immunity the levels of maternal antibodies in offspring at birth decreases and the projected duration of the protection afforded by maternal antibodies among their infants also decreases.
SOURCE: Waaijenborg S, et al. Waning of maternal antibodies against measles, mumps, rubella, and varicella in communities with contrasting vaccination coverage. J Infect Dis 2013;208:10-16.
A large cross-sectional serologic study was conducted in the Netherlands during 2006-2007 to compare kinetics of maternally-acquired antibodies in offspring. A total of 19,781 participants were invited in a nationwide survey of 40 communities selected at random, weighted by their population size. An age-stratified sample of 380-500 participants (less than 80 years of age) was drawn at random from each of these communities, with the sample size dependent on the response rate of each community. For a comparison group, participants were recruited from eight predominantly orthodox Protestant communities where vaccination coverage is low. An age-stratified sample of 380-952 participants (less than 80 years of age) was drawn at random from each of these communities. Vaccination histories of the infant participants were verified by vaccination certificates brought by the mothers and, where possible, a copy of the regional vaccine administration offices archives.
Antibody levels of IgG against measles, mumps, rubella, and varicella were determined by florescent bead-based multiplex immunoassays using Luminex technology (based on complete virus particles).
For measles, there was a large difference in vaccination coverage of women of childbearing age with 51.2% vaccinated in the general population versus 12.6% in the orthodox Protestant communities. Women of childbearing age and infants in the general population had a lower measles antibody concentration than infants and women of childbearing age in the orthodox Protestant communities (P #lt; 0.0001). The concentration of maternal antibodies in offspring at birth was 4.13-fold lower in the general population compared to the orthodox Protestant communities. The decay rate for maternal measles antibody was 7.77 per year, which corresponds to a half-life about one month. The projected duration of protection against measles was 3.3 months for newborns in the general population and 5.3 months for newborns in the orthodox Protestant communities.
For mumps, there was a smaller difference in vaccination coverage of women of childbearing age with 25.3% vaccinated in the general population versus 10.1% in the orthodox Protestant communities. There were not statistically significant differences in antibody levels between two groups. The decay rate for maternal mumps antibody was 8.01 per year, which corresponds to a half-life of about one month. The projected duration of protection against mumps was 2.7 months for newborns in both study groups.
For rubella, there was a large difference in vaccination coverage of women of childbearing age with 65.6% vaccinated in the general population versus 17.2% in the orthodox Protestant communities. The concentration of maternal antibodies in offspring at birth was 55.19-fold lower (95% CI, -6.22 to 116.60; P = 0.0296) in the general population compared to the orthodox Protestant communities. The decay rate for maternal rubella antibody was 7.01 per year, which corresponds to a half-life of about one month. The projected duration of protection against rubella was 3.9 months for newborns in the general population and also in the orthodox Protestant communities.
For varicella, no participants had been vaccinated and the level of varicella antibodies did not differ between the two study groups. The decay rate of maternal verso antibodies was 7.36 per year, with the duration of protection against personal of 3.4 months for newborns of both groups.
COMMENTARY
This study confirms that infants of vaccinated mothers lose protection from maternal antibodies against measles, mumps and rubella well before 12-15 months of age when the first dose of MMR is recommended. The decay rates of 7.77, 8.01, and 7.01 per year of maternal measles, mumps and rubella antibodies, respectively, implies that each month the concentration of maternally-acquired antibodies is reduced by about half. With the lower level of maternal antibodies of birth, the period of protection decreases by almost 2 months. Indeed, this is evidenced by a shift in the incidence of measles to frequently include children less than 12 months of age.
The comparison of the two groups suggests that as MMR vaccination coverage among mothers increases, compared to mothers with natural immunity the levels of maternal antibodies in offspring at birth decreases and the projected duration of the protection afforded by maternal antibodies among infants also decreases. The basis for this is likely two-fold: MMR vaccine induces lower levels of antibodies than natural infection with measles, mumps, and rubella; and vaccinated individuals are no longer boosted by exposure to wild-type infections.
The optimal timing of the first MMR vaccination is before likely exposure to diseasebut a satisfactory immune response is dependent on maturation of the infant's immune system to respond to vaccine antigens, and when the decay of maternal antibodies is sufficient to ensure that they do not interfere and neutralize the live, attenuated vaccine strains. This balance is why the recommended age of MMR vaccination was modified in 1998 to 12-15 months of age (from 15 months of age) to reflect the impact of MMR vaccination and decreased antibody titers among women of child-bearing age.
