Quantification of Waning Immunity After Measles Vaccination-Evidence From a Seroprevalence Study

We aimed to quantify rates of waning immunity after measles vaccination from seroprevalence data collected in a study of a population with high vaccination coverage and a fixed vaccination schedule. Data were collected during a national survey (the Immunological Survey) carried out in the Slovak Republic in 2018. The average rate of waning immunity against measles after the first dose of measles, mumps, and rubella (MMR) vaccine (ages 1.5-10 years) was 9.7% per year from the geometric mean titer value of 2,634 mUI/mL. The average waning rate after the second dose of MMR vaccine (ages 10-33 years) was significantly lower: 4.8% per year from the lower geometric mean titer of 1,331 mUI/mL. This decline in antibody levels suggests that vaccine-induced protection may be compromised and results in an increase in the proportion of seronegative/borderline individuals. These outcomes may provide a valuable source for critical assessment of direct and indirect effects of MMR vaccination.

Measles immunity in a Czech tertiary care hospital

BACKGROUND

Given the increasing incidence of measles, the aim was to assess the seroprevalence of measles immunity among employees of a Czech tertiary care hospital and to assess their willingness to revaccination.

METHODS

3027 hospital employees (2421 females, 606 males) underwent a serological analysis of their measles antibody levels with an option of revaccination in case of an insufficient level.

RESULTS

The median age of participants was 42 years. Seropositivity was noted in 54% of the participants, with the antibody values higher in the oldest study participants and with a decrease around the birth year 1968. Logistic regression analysis confirmed a significant relationship of seropositivity with age (odds ratio 0.97, p < 0.005). Out of the seronegative, 80.9% individuals got revaccinated.

CONCLUSIONS

46% of the participants did not reach a sufficient antibody level set by the assay's manufacturer. Although the routine vaccination system is well established it may be ineffective.

Sero-epidemiological study in prediction of the risk groups for measles outbreaks in Vojvodina, Serbia

Background

Age-stratified serologic surveys provide insight into the gaps of measles-specific immunity as well as estimates of the age-specific seroprevalence. The aim of this study was to describe the measles sero-epidemiology in Vojvodina before the occurrence of outbreak in 2017/18 and to discuss preventive measures for potential future epidemics.

Methods

A seroprevalence study was conducted from April 2015 to June 2017 on serum bank of 3199 residual samples. Study was performed prior to the last measles outbreak in Vojvodina that occurred between 12th November 2017 and 30th June 2018. Measles-specific IgG antibodies were determined using an indirect chemiluminescent immunoassay (CLIA).

Results

Median age of enrolled participants was 20 years (IQR 11–37). Overall, 86.9% serum samples were seropositive. The highest proportion of measles seronegativity was observed in children aged 12–23 months of age and in adults aged 20–39 years (56.1% and 18.5%, respectively). Prevalence of measles seronegativity above WHO target levels susceptibility was observed in the following age groups: 2, 7, 13, 15, and among all adults aged between 20 and 49 years. Out of total measles outbreak cases (177), there were 91 (51.4%) participants aged 20–39 years. A significant positive correlation was observed between measles seronegativity and the number of reported measles cases aged ≥ 12 months (r = 0.4675, p = 0.0213).

Conclusions

In order to prevent new outbreaks and achieve the elimination of measles in Vojvodina, the vaccination coverage of both measles-mumps-rubella (MMR1 and MMR2) vaccines needs to be improved and sustained. Educational campaigns for the improvement of acceptance and timely vaccination with vaccine against measles among doctors and the general population are crucial. Our results indicate possible gap in measles protection in adults born during implementation of one dose of measles vaccine and prioritize supplementary immunization activities targeting adults in Vojvodina, Serbia.

Screening of more than 2000 Hungarian healthcare workers' anti-measles antibody level: results and possible population-level consequences

Due to the European measles epidemic and the increased number of imported cases, it can be theorised that the risk of exposure among Hungarian healthcare workers (HCWs) has increased. In 2017, the increased measles circulation in the region led to the emergence of smaller local and hospital epidemics. Therefore, our objective was to determine the herd immunity in the high-risk group of HCWs. A hospital-based study of detecting anti-measles IgG activity was performed in 2017 and included 2167 employees of the Military Medical Centre (Hungary). The screening of HCWs presented a good general seropositivity (90.6%). The highest seroprevalence value (99.1%) was found in the age group of 60 years or older. The lowest number of seropositive individuals was seen in the 41-45 years (86.2%) age group, indicating a significant herd immunity gap between groups. Regarding the Hungarian data, there might be gaps in the seroprevalence of the analysed HCWs, implying that susceptible HCWs may generate healthcare-associated infections. This study suggests that despite the extensive vaccination and high vaccine coverage, it is still important to monitor the level of protective antibodies in HCWs, or in a representative group of the whole population of Hungary, and possibly in other countries as well.