Measles-mumps-rubella vaccine at 6 months of age, immunology, and childhood morbidity in a high-income setting: study protocol for a randomized controlled trial

Comparison of measles plaque reduction neutralization test (PRNT) and measles virus-specific IgG ELISA for assessment of immunogenicity of measles-mumps-rubella vaccination at 5-7 months of age and maternal measles antibodies

Background

Assessing the risk of measles outbreaks and identifying the susceptible parts of the population is essential to timely intervention. Infants between 6-12 months are increasingly susceptible to measles but evaluating the performance of high throughput enzyme immunoassays (ELISAs) in infants < 9 months of age is lacking.

Methods

A commercially available ELISA kit (Creative Diagnostics, DEIA359) for estimating measles seroprotection was evaluated in infants 5-7 months of age. In an immunogenicity substudy in the Danish MMR trial conducted between 2019-2021, infants (and mothers at baseline) were sampled before and one month after measles-mumps-rubella vaccination (MMR) or placebo as well as one month after routine MMR at 15 months. Measles IgG ELISA was compared to the gold standard but labor-intensive measles plaque reduction neutralization test (PRNT) by Pearson and Spearman correlations and by estimating sensitivity, specificity, and positive and negative predictive values (PPV and NPV).

Findings

Measles IgG levels compared to PRNT antibodies had a Pearson's correlation coefficient between 0.10-0.24. Seroprotection rates measured by ELISA in young infants were 10-14% lower than measured by PRNT. The sensitivity of the ELISA to detect serological protection compared to PRNT in the infant population differed markedly across sampling time points and was 14%, 40%, and 92% at baseline, post-intervention, and post-routine MMR, whereas the specificity was 99%, 93%, and 43%, respectively. The PPV and NPV were 68% and 87% in infants at baseline.

Interpretation

The correlation between measles IgG and PRNT antibodies was low. Seroprotection was underestimated using ELISA. High-accuracy tests are needed to avoid misclassifications and practices that lead to primary or secondary vaccine failure or retention of vaccination in outbreak settings. Baseline PPV and NPV suggested some applicability of ELISA in predicting serological protection in this age group. However, PRNT may be the only accurate estimator of serological protection in young infants.

Immunogenicity and reactogenicity following MMR vaccination in 5-7-month-old infants: a double-blind placebo-controlled randomized clinical trial in 6540 Danish infants

Background

Measles is a highly contagious viral disease. Vaccinated mothers transfer fewer antibodies during pregnancy, resulting in shortened infant immunity. Earlier primary vaccination might avert the gap in protection.

Methods

Healthy 5-7-month-old Danish infants were assigned in a 1:1 ratio to M-M-RVaxPro or placebo (solvent) in a double-blind, randomized trial between April 15, 2019 and November 1, 2021 (ClinicalTrials.govNCT03780179, EudraCT 2016-001901-18). Eligibility criteria were birth weight >1000 g and gestational age ≥32 weeks.Immunogenicity was measured by plaque reduction neutralization test (PRNT) and IgG ELISA before intervention, four weeks after intervention and routine MMR. Reactogenicity data were collected for six weeks and measured by hazard ratios (HR).

Findings

647 and 6540 infants participated in the immunogenicity and reactogenicity study, respectively; 87% and 99% completed follow-up. After early MMR, seroprotection rates (SPRs) were 47% (13%) in measles PRNT; 28% (2%), 57% (8%) in mumps and rubella IgG (placebo). For measles PRNT, geometric mean ratio was 4.3 (95% CI: 3.4-5.3) between randomization groups after intervention and 1.5 (95% CI: 1.3-1.9) after routine MMR.Reactogenicity was independent of randomization (HR, 1.0; 95% CI: 0.9-1.1). Severe adverse events occurred in 25 infants (HR, 1.8; 95% CI: 0.8-4.0); none deemed vaccine related.

Interpretation

Early MMR elicited low SPRs but did not negatively impact short-term responses to a subsequent MMR. MMR at 5-7 months was safe and not associated with higher rates of reactogenicity than placebo.

Funding

Innovation Fund Denmark.

Measles, mumps, and rubella vaccine at age 6 months and hospitalisation for infection before age 12 months: randomised controlled trial

OBJECTIVE

To test for potential non-specific effects of an additional, early measles, mumps, and rubella (MMR) vaccine at age 5-7 months on risk of infection related hospitalisation before age 12 months.

DESIGN

Randomised, double blinded, placebo controlled trial.

SETTING

Denmark, a high income setting with low exposure to MMR.

PARTICIPANTS

6540 Danish infants aged 5 to 7 months.

INTERVENTIONS

Infants were randomly allocated 1:1 to intramuscular injection with standard titre MMR vaccine (M-M-R VaxPro) or placebo (solvent only).

MAIN OUTCOME MEASURES

Hospitalisations for infection, defined as all hospital contacts of infants referred from primary care for hospital evaluation and with an infection diagnosed, analysed as recurrent events, from randomisation to 12 months of age. In secondary analyses implications of censoring for date of subsequent diphtheria, tetanus, pertussis, polio, Haemophilus influenzae type B, and immunisation with pneumococci conjugate vaccine (DTaP-IPV-Hib+PCV), potential effect modification by sex, prematurity (<37 weeks' gestation), season, and age at randomisation were tested, and the secondary outcomes of hospitalisations ≥12 hours and antibiotic use were evaluated.

RESULTS

6536 infants were included in the intention-to-treat analysis. 3264 infants randomised to MMR vaccine experienced 786 hospitalisations for infection before age 12 months compared with 762 for the 3272 infants randomised to placebo. In the intention-to-treat analysis the rate of hospitalisations for infection did not differ between the MMR vaccine and placebo groups (hazard ratio 1.03, 95% confidence interval 0.91 to 1.18). For infants randomised to MMR vaccine compared with those randomised to placebo, the hazard ratio of hospitalisations for infection with a duration of at least 12 hours was 1.25 (0.88 to 1.77), and for prescriptions of antibiotics was 1.04 (0.88 to 1.23). No significant effect modifications were found by sex, prematurity, age at randomisation, or season. The estimate did not change when censoring at the date infants received DTaP-IPV-Hib+PCV after randomisation (1.02, 0.90 to 1.16).

CONCLUSION

Findings of this trial conducted in Denmark, a high income setting, do not support the hypothesis that live attenuated MMR vaccine administered early to infants aged 5-7 months decreases the rate of hospitalisations for non-targeted infection before age 12 months.

TRIAL REGISTRATION

EU Clinical Trials Registry EudraCT 2016-001901-18 and ClinicalTrials.gov NCT03780179.

Genetics and measles, mumps and rubella vaccine response in childhood and adolescence-A systematic review

Measles, mumps and rubella (MMR) are contagious infectious diseases that can be prevented by immunization. However, MMR infections can occur in previously immunized individuals. The vaccine response is, among other factors, influenced by the combined effects of many genes. This systematic review investigates the genetic influence on measles, mumps and rubella antibody responses after childhood vaccination. In accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA), systematic literature searches were conducted in the medical databases PubMed, EMBASE and PsycINFO. Search strings were adjusted for each database. Citations were included if they measured and compared the immune response with immunogenetics after vaccination with a vaccine containing one or more of the following components: measles, mumps and/or rubella, MMR. The measure of vaccine response studied was antibodies after vaccination. Forty-eight articles were included in the final analysis. The results suggest that genetic determinants, including host genes, and single nucleotide polymorphisms in immune-related genes influence the MMR antibody responses after vaccination. Specifically, replicated associations were found between HLA, CD46, RARB, IRF9, EIF2AK2, cytokine genes and MMR vaccine-induced humoral immune responses. This knowledge can be useful in understanding and predicting immune responses and may have implications for future vaccine strategies.

Parents' and Health Professionals' Attitudes to Advancing Primary MMR Vaccine Administration from Fifteen to Six Months of Age-A Qualitative Thematic Analysis Embedded in a Randomized Trial

Declining levels and duration of passively acquired maternal antibodies prompted a Danish trial to test the feasibility of advancing administration of the first measles, mumps, and rubella vaccine (MMR1) from 15 to 6 months of age. A trial-embedded qualitative study aimed to understand parents' (N = 24) and health professionals' (N = 11) attitudes about the measles, mumps, and rubella vaccine (MMR) in general and about advancing MMR1 administration. Overly positive parent attitudes were contrasted by members of a vaccine-skeptical organization including parents considering that their child was seriously vaccine-injured long ago. Parents' attitudes to advancing MMR1 mirrored their attitudes about the MMR vaccine in general, with four positions along a continuum of trust in the healthcare system: unquestioning trust, acceptance after careful consideration, challenging indecisiveness, and defensive rejection. Low tolerance was identified between vaccine supporters and vaccine opponents. Parents of children with perceived serious vaccine-related injuries described lifelong unresolved feelings of guilt. Supporters of advanced MMR1 saw it as a timely and convenient administration of a well-known vaccine, whereas opponents feared it would disturb the children's immature immune systems and emphasized difficulties in recognizing side effects so early in life. Health professionals were supportive of advancing the MMR1 vaccine and they carefully challenged the parents. Current MMR vaccine supporters show readiness to advance MMR1 administration.