Rubella antibodies in cord blood sera in Portugal: association with maternal age and vaccination status

Antibodies to measles, mumps, and rubella virus in Thai children after two-dose vaccination at 9 months and 2.5 years: A longitudinal study

INTRODUCTION

Thailand changed the schedule of childhood measles-mumps-rubella (MMR) vaccination in 2014, moving the second dose from the age of 6 years to 2.5 years. There are currently no data on antibody responses to the MMR vaccine since this recommendation.

MATERIAL AND METHODS

We investigated antibody responses in a cohort of children who received two doses of MMR vaccine at the ages of 9 months and 2.5 years that was originally established to evaluate antibody levels to Bordetella pertussis antigens (ClinicalTrials.gov no. NCT02408926). Infants were born to mothers who previously received tetanus-diphtheria-acellular pertussis vaccine at 27-36 weeks of gestation. Anti-measles, -mumps, and -rubella virus IgG levels were measured at birth (cord blood) and the ages of 2 and 7 months (before the first MMR vaccination); 18 and 24 months (9 and 15 months, respectively, after the first dose); and 36 months (6 months after the second dose) using commercially available enzyme-linked immunosorbent assay kits.

RESULTS

At 7 months of age, 96.2%, 99.6%, and 98.8% of infants had no protection against measles, mumps, and rubella, respectively. Levels of antibody against all three antigens increased significantly after the first but not the second dose. At 6 months after two-dose vaccination, 97.4%, 84.8%, and 78.7% of children remained seroprotected against measles, mumps, and rubella, respectively.

CONCLUSIONS

Maternally derived antibodies to measles, mumps, and rubella virus disappeared by the age of 7 months in Thai children. Two-dose MMR vaccination at 9 months and 2.5 years of age induced robust immune responses against these viruses.

Mumps antibodies in the cord blood: Association with maternal recall of mumps. Possible consequences for vaccination strategies

The present study aims to contribute to the evaluation of the serological impact of vaccination against mumps in Portugal, measuring anti-mumps IgG (MuIgG) levels in cord sera and the corresponding proportions of seropositive newborns, and their association with potential predictive variables. The data from this study came from 198 umbilical cord sera. Detailed vaccination records were available for all mothers. MuIgG were measured in the sera, using a commercial immunoassay. The geometric mean concentration (GMC) of MuIgG was 31.7 RU/ml. Seropositive/immune sera (concentration ≥16 RU/ml) were 75.3%. While 49 mothers were "unsure" about ever having had mumps, 46 said they had had the disease and 103 said they had not had it. Eighty eight women did not receive a single dose of MMR while the other received 1 or 2 doses, with different combinations of vaccine strains. This study found that recalling mumps was predictive of higher MuIgG GMC and seropositivity. Maternal age and vaccination status were not associated with GMC or seropositivity. Nevertheless, in the small subset of newborns from vaccinated mothers not recalling mumps, receiving two doses was predictive of higher GMC than just receiving one. Maternal recall of mumps is highly predictive of seropositivity while not recalling the disease results in numerous false-negatives. This is consistent with other studies and with the fact that infection with mumps virus can result in a wide range of clinical manifestations. We agree on the need for further research to support a recommendation of a three (or more)-dose MMR strategy but we also believe that evidence is fast accumulating in favour of a higher dose strategy. The issue of waning immunity due to vaccines when vaccination succeeds in controlling (and nationally eliminating) target diseases like measles and mumps must be urgently taken into account.