Measles Virus Neutralizing Antibody Response, Cell-Mediated Immunity, and Immunoglobulin G Antibody Avidity Before and After Receipt of a Third Dose of Measles, Mumps, and Rubella Vaccine in Young Adults.

BACKGROUND: Two doses of measles, mumps, and rubella (MMR) vaccine are 97% effective against measles, but waning antibody immunity to measles and failure of the 2-dose vaccine occur. We administered a third MMR dose (MMR3) to young adults and assessed immunogenicity over 1 year. METHODS: Measles virus (MeV) neutralizing antibody concentrations, cell-mediated immunity (CMI), and immunoglobulin G (IgG) antibody avidity were assessed at baseline and 1 month and 1 year after MMR3 receipt. RESULTS: Of 662 subjects at baseline, 1 (0.2%) was seronegative for MeV-neutralizing antibodies (level, <8 mIU/mL), and 23 (3.5%) had low antibody levels (8-120 mIU/mL). One month after MMR3 receipt, 1 subject (0.2%) was seronegative, and 6 (0.9%) had low neutralizing antibodies, with only 21 of 662 (3.2%) showing a ≥ 4-fold rise in neutralizing antibodies. One year after MMR3 receipt, no subject was seronegative, and 10 of 617 (1.6%) had low neutralizing antibody levels. CMI analyses showed low levels of spot-forming cells after stimulation, suggesting the presence of T-cell memory, but the response was minimal after MMR3 receipt. MeV IgG avidity did not correlate with findings of neutralization analyses. CONCLUSIONS: Most subjects were seropositive before MMR3 receipt, and very few had a secondary immune response after MMR3 receipt. Similarly, CMI and avidity analyses showed minimal qualitative improvements in immune response after MMR3 receipt. We did not find compelling data to support a routine third dose of MMR vaccine.

Persistence of measles antibodies after 2 doses of measles vaccine in a postelimination environment.

OBJECTIVE: To evaluate the persistence of measles antibodies after 2 doses of measles vaccine in a setting where exposure to wild-type measles was unlikely. Measles was declared eliminated from the United States in 2000, an achievement attributed to effective implementation of a routine 2-dose vaccination policy. Some have questioned whether measles transmission could resume if immunity wanes in the absence of boosting from wild-type measles. DESIGN: Prospective, observational, volunteer cohort study. SETTING: Rural Wisconsin health maintenance organization. PARTICIPANTS: Children who received the second measles vaccine dose at kindergarten (aged 4-6 years) or middle school (aged 10-12 years) in 1994 or 1995. Serum samples were collected periodically during a 10-year period for the kindergarten group and a 5-year period for the middle school group. INTERVENTION: Second dose of measles vaccine. MAIN OUTCOME MEASURE: Measles antibody levels were assessed by plaque-reduction neutralization: titers less than 8 mIU/mL were considered seronegative and suggestive of susceptibility to measles, and titers of 120 mIU/mL or less were considered low and suggestive of potential susceptibility. RESULTS: During the study period, no measles was reported in the study area. Voluntary attrition reduced the study population from 621 at enrollment to 364 (58.6%) by study end. Before the second dose, 3.1% (19/621) had low titers, of whom 74% (14/19) were antibody-negative, with geometric mean titers being significantly higher in kindergarteners (1559 mIU/mL) than in middle schoolers (757 mIU/mL) and rates of negativity significantly lower (1.0% [3/312] vs 3.6% [11/309]). One month after the second dose, 0.2% (1/612) had low titers and none was seronegative, with geometric mean titers being significantly higher in kindergarteners (2814 mIU/mL) than in middle schoolers (1672 mIU/mL). By study end, 4.9% (18/364) had low titers and none was seronegative, with no significant difference in geometric mean titers between kindergarteners (641 mIU/mL) and middle schoolers (737 mIU/mL) when both groups were aged 15 years. Projections suggest that the proportion of persons with low antibody levels may increase over time. CONCLUSIONS: Measles antibody persisted in all vaccinees available for follow-up 10 years after a second dose of vaccine, with no seronegative results detected. Declining titers suggest the need for vigilance in ensuring disease protection for the vaccinated population.

Follow-up of infants given measles vaccine at 6 months of age: antibody and CMI responses to MMRII at 15 months of age and antibody levels at 27 months of age.

The worldwide elimination of measles is an important target. In developed countries, to control measles outbreaks, immunization from 6 months of age is recommended. In this study, infants (n = 290) who were (1) born to mothers with natural immunity or to vaccinated mothers and (2) previously immunized with Connaught (CLL) or AIK-C measles vaccine at 6 months of age, were evaluated for measles immunity before and after measles-mumps-rubella (MMRII at 15 months of age. Eight weeks after MMRII, 98.9% of infants were seropositive by enzyme immunoassay (EIA) and 70% demonstrated measles specific cellular immunity by blast transformation (BT) of lymphocytes. At 27 months of age, 98.4% of infants had protective antibody levels by plaque reduction neutralization (PRN) test. These results suggest that AIK-C and CLL vaccines elicit durable protective immunity in young infants when used in early immunization programs.

Humoral and cell-mediated immune responses to an early 2-dose measles vaccination regimen in the United States.

BACKGROUND: Shifts in peak measles incidence to children <12 months old and the associated high mortality support the study of an early 2-dose measles vaccine regimen. METHODS: Fifty-five infants were vaccinated with measles vaccine at age 6 (n=32) or 9 (n=23) months, followed by measles-mumps-rubella (MMR)-II vaccine at age 12 months. A control group received MMR-II only at age 12 months. Measles-specific humoral and cell-mediated immunity were evaluated before, 12 weeks after measles immunization, and 24 weeks after MMR-II. RESULTS: Measles-specific T cell proliferation after both doses of vaccine was equivalent, regardless of age or the presence of passive antibodies. Seroconversion rates, geometric mean titers, and the percentage of infants with antibody titers >120 mIU after the first measles vaccine were lower in infants vaccinated at age 6 months, regardless of the presence of passive antibodies, but measles humoral responses increased after the administration of MMR-II vaccine in children initially vaccinated at age 6 or 9 months. CONCLUSION: Measles vaccination elicits T cell responses in infants as young as 6 months old, which may prime the humoral response to the second dose. Initiating measles vaccination as an early 2-dose regimen results in an immunologic response that is likely to have clinical benefits in developed and developing countries.

Measles and mumps vaccination as a model to investigate the developing immune system: passive and active immunity during the first year of life.

Evaluations of neutralizing antibody responses in 6-, 9- and 12-month-old infants given measles or mumps vaccine indicated that 6-month-old infants had diminished humoral immune responses associated with passive antibody effects, but also had an intrinsic deficiency in antiviral antibody production, which was independent of passive antibody effects. In contrast, lower neutralizing antibody titers in 9-month-olds were related only to passive antibody effects. Measles and mumps-specific T-cell proliferation and interferon-gamma (IFNgamma) production were induced by vaccination at 6, 9 or 12 months, regardless of passive neutralizing antibodies or age. These observations suggest a need to refine concepts about passive antibody interference and primary vaccine failure, taking into account the sensitization of antiviral T-cells, which occurs in the presence of passive antibodies and is observed in infants who do not develop active humoral immunity. A second dose of measles vaccine given at 12-15 months enhanced antiviral T-cell responses to measles in infants who were vaccinated at 6 or 9 months, and produced higher seroconversion rates. Since T-cell immunity is elicited under the cover of passive antibodies, the youngest infants benefit from the synergistic protection mediated by maternal antibodies and their own capacity to develop sensitized antiviral T-cells, which prime for subsequent exposures to the viral antigens. Conceptually, maternal immunization approaches with vaccines that can be given to women of child-bearing age before pregnancy, or that are safe for administration during pregnancy, should enhance passive antibody protection. Rather than being detrimental to infant adaptive immune responses, maternal vaccination can be coupled effectively with vaccine regimens that elicit priming of antiviral immune responses in infants during the first year of life.