Measles-mumps-rubella revaccination; 18 months vs. 4-6 years of age: potential impacts of schedule changes

Seroconversion rates following 2 doses of measles- mumps- rubella vaccination given at the ages 12 and 18 months: data for possible additional dose at older age

Background

Despite high rate of vaccination coverage with 2-doses of measles containing vaccine among Iranian children, outbreaks of measles occurred among different age groups and fully vaccinated subjects. Although the main reason for these outbreaks is unknown, however, vaccine failure was supposed to be an important cause. This study was designed to determine the seroconversion rates to measles- mumps- rubella (MMR) vaccine currently in use among Iranian children.

Methods

This prospective study was conducted among healthy children older than 12 months who were candidates of scheduled MMR vaccination. Blood samples were obtained from each mother- infant pair just before vaccination, and from infants 4–6 weeks after MMR₁ and MMR₂ immunization. Collected sera were tested for specific lgG antibodies against MMR agents using ELISA method. The proportion of seroprotected subjects among mother- infant pairs before vaccination as well as the prevalence rates of seroconversion after MMR₁ and MMR₂ vaccination were calculated. Collected data were analyzed using descriptive statistical methods.

Results

During 22-months study period, 92 mother- infant pairs were participated. Seroimmunity rates against MMR viruses were 85.8%, 84.7% and 86.9% for mothers, and 3.2%, 2.1% and 1.0% for children, respectively. After MMR₁ vaccination from 52 seronegative children, 80.7%, 78.8% and 75% were seroconverted. These rates increased to 94.8%, 89.7% and 94.8% after the MMR₂ vaccination. Also, the specific immunity was enhanced among seropositive children.

Conclusion

Majority of the mothers and few infants were immune to MMR viruses prior to MMR₁ vaccination. Immune responses detected after MMR₁ injection, and overall seroconversion rates achieved after 2-doses of MMR vaccination were less than expected and inadequate to preserve long-term protection against MMR agents.

Position statement of the Spanish Society of Pediatric Rheumatology on infection screening, prophylaxis, and vaccination of pediatric patients with rheumatic diseases and immunosuppressive therapies: Part 1 (screening)

This study provides practical recommendations on infection screening in pediatric patients with immune-mediated rheumatic diseases and immunosuppressive therapies. For this reason, a qualitative approach was applied. A narrative literature review was performed via Medline. Primary searches were conducted using Mesh and free texts to identify articles that analyzed data on infections and vaccinations in pediatric patients with immune-mediated rheumatic diseases and immunosuppressive therapies. The results were presented and discussed in a nominal group meeting, comprising a committee of 12 pediatric rheumatologists from the infections prevention and treatment working group of the Spanish Society of Pediatric Rheumatology. Several recommendations were generated. A consensus procedure was implemented via a Delphi process that was extended to members of the Spanish Society of Pediatric Rheumatology and Vaccine Advisory Committee of the Spanish Association of Pediatrics. Participants to the process produced a score ranging from 0 = totally disagree to 10 = totally agree. Agreement was considered if at least 70% of participants voted ≥ 7. The literature review included more than 400 articles. Overall, 63 recommendations were generated (21 on infection screening) voted by 59 pediatric rheumatologists and other pediatric specialists, all of them achieving the pre-established agreement level. The recommendations on screening cover all the procedures (serology, assessment of risk factors, and other clinical activities) connected with the screening for infections including tuberculosis; hepatitis A, B, and C viruses; measles; mumps; rubella; diphtheria; and other infections. Conclusion: Screening for infections is an essential part of risk management in pediatric patients with immune-mediated rheumatic diseases and immunosuppressive therapies. What is Known: • Infectious diseases and related complications are a major cause of morbidity and mortality in patients with immune-mediated rheumatic diseases. • At present, practical information on infectious prophylaxis in children with rheumatic diseases is limited, and often extrapolated from children with cancer. What is New: • In the absence of evidence, a literature review and a Delphi survey were conducted to establish a series of expert recommendations that would be useful in clinical practice, providing a practical and simple day-to-day approach to be used by pediatric rheumatologists.

Measles and rubella serosusceptibity among population vaccinated with different schedules: the potential impact on measles-rubella elimination in Iran

BACKGROUND

Iranian children were vaccinated with the scheduled two doses of monovalent measles vaccine (mMV) from 1984. In December 2003, a nationwide campaign of measles-rubella (MR) immunization was established to vaccinate 5-25 year- old individuals. In 2004, the mMV was replaced with measles- mumps- rubella (MMR) vaccine. Despite the high vaccination coverage, the outbreaks of measles still occur in the country. In this Study, the MR immunity status of various age groups, vaccinated with different schedules was investigated, and the immunologic response of seronegative subjects to revaccination was examined.

METHODS

This cross-sectional study was conducted among 7-33-year-old healthy individuals with a documented history of measles vaccination from November 2017 to June 2018. The subjects were categorized as follows: group A, including 20-33 year-old individuals; vaccinated with 1-2 doses of mMV at ages 9 and 15 months, and revaccinated with MR, group B, including 15-19-year-old individuals, vaccinated with two doses of mMV at 9 and 15 months of age, and received additional dose of MMR upon school entrance, group C, including 11-14 year-old individuals, vaccinated with two-doses of MMR at the ages of 15 months and 6 years, and group D, including 7-10 year-old individuals vaccinated with two-doses of MMR vaccine at the ages 12 and 18 months, respectively. Levels of antimeasles- antirubella IgG antibodies in the collected sera were measured. Also antimeasles- antirubella IgM and IgG of seronegative individuals were reexamined at 4-6 weeks after MMR revaccination. The collected data were analyzed using descriptive statistical methods.

RESULTS

A total of 635 individuals were investigated in this study. Group A, 98; group B, 295; group C, 139; and group D, 103 persons. Overall, 12.3 and 18.4% of the population were seronegative for measles and rubella antibodies. This rate varied greatly between the 4 groups: group A, 0/0-2%; group B,15.2-25.0%; group C,11.5-17.2%; and groupD,14.6-18.4%. After revaccination, 92 and 94.9% of seronegative individuals showed IgG response to measles and rubella vaccines, respectively.

CONCLUSION

Despite the high coverage rate of M-R containing vaccines, a significant number of vaccinated subjects were seronegative for measles and rubella, possibly because of secondary vaccine failure; this may negatively affect measles-rubella elimination targets in the country. If these findings are confirmed in similar future studies, a more robust regional/national supplementary immunization activity will be considered.

Systematic Review of Measles and Rubella Serology Studies

Serological tests provide information about individual immunity from historical infection or immunization. Cross-sectional serological studies provide data about the age- and sex-specific immunity levels for individuals in the studied population, and these data can provide a point of comparison for the results of transmission models. In the context of developing an integrated model for measles and rubella transmission, we reviewed the existing measles and rubella literature to identify the results of national serological studies that provided cross-sectional estimates of population immunity at the time of data collection. We systematically searched PubMed, the Science Citation Index, and references we identified from relevant articles published in English. We extracted serological data for comparison to transmission model outputs. For rubella, serological studies of women of child-bearing age provide information about the potential risks of infants born with congenital rubella syndrome. Serological studies also document the loss of maternal antibodies, which occurs at different rates for the different viruses and according to the nature of the induced immunity (i.e., infection or vaccine). The serological evidence remains limited for some areas, with studies from developed countries representing a disproportionate part of the evidence. The collection and review of serological evidence can help program managers identify immunity gaps in the population, which may help them better understand the characteristics of individuals within their populations who may participate in transmission and manage risks.