Seroprevalence of measles, mumps, and rubella and genetic characterization of mumps virus in Khartoum, Sudan

Assessing measles immunity among healthcare workers, a systematic review of peer-reviewed literature (2013-2023). Where do we go from here?

BACKGROUND

Measles, a highly contagious disease, is experiencing a global resurgence, posing significant risks to healthcare workers (HCWs) due to occupational exposure. While previous studies have primarily evaluated HCW immunity using seroprevalence, no study has comprehensively assessed immunity by incorporating other widely used definitions, including documented evidence of immunity, natural immunity by birth cohort, and self-reported immunity.

METHODS

A systematic review was conducted of HCW immunity surveillance studies published in English in peer-reviewed journals from January 2013 to February 2024. Data were extracted on (1) country, (2) author and year, (3) immunity assessment type, (4) study type, (5) data collection period, (6) immunity coverage results, (7) HCW count, (8) age ranges, (9) job roles, and (10) seroprevalence methodology and threshold values, where applicable.

RESULTS

A total of 98 studies were included, with immunity coverage ranging from 57.1 % to 99.2 %. Immunity assessments were based on seroprevalence, documented evidence, natural immunity by birth cohort, and self-reported immunity. Considerable heterogeneity was observed across study populations, immunity assessment methodologies, and situational contexts, including studies conducted during outbreaks. Studies included demonstrated that recall may underestimate immunity, as a high rate of seropositivity was observed among participants who did not remember being vaccinated or having measles.

CONCLUSION

This study highlights a positive trend in HCW immunity coverage compared to previous findings. However, significant methodological variability in assessing measles immunity limits the ability to perform aggregated global analyses. Studies using only one method to assess immunity contribute to the perception of lower-than-expected immunity coverage, as this limited approach may not provide a complete or accurate picture of actual immunity levels. Future research should prioritize the development of standardized tools and methodologies to enable data harmonization and facilitate robust global immunity assessments.

Evaluation of SARS-CoV-2 Antibody Response Between Paired Fingerprick (HemaPEN®) and Venepuncture Collected Samples in Children and Adults

Serological surveillance of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies is important to monitor population COVID-19 immunity. Dried blood spots (DBS) are a valuable method for serosurveys, particularly in remote settings and in children. We compared the measurement of SARS-CoV-2 spike-specific IgG in paired blood samples collected using standard venepuncture (serum) and the hemaPEN® microsampling DBS device from children and adults. A total of 83 participants (10 months to 65 years of age), comprising COVID-positive and -negative participants, were recruited. Paired serum and DBS samples were assayed for SARS-CoV-2 receptor-binding domain (RBD) and Spike (S1) antibodies using an established in-house ELISA. RBD and S1 IgG concentrations of paired hemaPEN DBS eluates and serum samples were compared using a non-parametric Wilcoxon matched-pairs signed ranked test. A Pearson's correlation was used for RBD and S1 IgG concentrations and the level of agreement between the hemaPEN DBS eluates and serum samples was assessed by Bland-Altman analysis. A total of N = 41 adults (36 COVID-positive and 5 COVID-negative), and N = 42 children (37 COVID-positive, and 5 COVID-negative) have paired serum and DBS assayed. We found moderate to strong correlations between paired hemaPEN DBS eluates and serum SARS-CoV-2 IgG antibodies for RBD (r = 0.9472, p < 0.0001) and S1 proteins (r = 0.6892, p < 0.0001). Similar results were observed in both adult and paediatric populations. No significant differences in S1-specific IgG levels were observed in hemaPEN DBS samples stored for up to 35 weeks at room temperature. Eluted hemaPEN samples showed high specificity and sensitivity (100% and 89.89%, respectively) compared with serum. The use of the microsampling hemaPEN device for DBS sample collection is a feasible approach for assessing SARS-CoV-2 antibodies for serosurveillance studies, particularly in remote settings and in children.

Serosurveillance for Measles and Rubella

Measles and rubella remain global health threats, despite the availability of safe and effective vaccines. Estimates of population immunity are crucial for achieving elimination goals and assessing the impact of vaccination programs, yet conducting well-designed serosurveys can be challenging, especially in resource-limited settings. In this review, we provide a comprehensive assessment of 130 measles and rubella studies published from January 2014 to January 2024. Methodologies and design aspects of serosurveys varied greatly, including sample size, assay type, and population demographics. Most studies utilized enzyme immunoassays for IgG detection. Sample sizes showed diverse sampling methods but favored convenience sampling despite its limitations. Studies spanned 59 countries, predominantly including adults, and revealed disparities in seroprevalence across demographics, regions, and notably among migrants and women. Age-related declines in antibodies were observed, particularly among infants, and correlations between vaccination status and seropositivity varied. We conclude with an outlook on measles and rubella serosurveillance, emphasizing the need for proper survey design and the advantages of standardized, multiplex serology assays.

Active circulation of varicella zoster virus among different age groups in Sudan

In Sudan, data on varicella infections are lacking and the vaccine is currently not in use. The aim of this study was to investigate previous exposure to varicella zoster virus (VZV) among children and adults from the general population and among health-care workers (HCWs) in Khartoum. Dried blood spot samples collected between 2015 and 2016 from 294 children aged 1‒15 years, 153 adult volunteers and 241 HCWs were investigated for the presence of VZV IgG antibodies using ELISA. The overall seroprevalence of VZV IgG antibodies among the investigated cohorts was 50.4%, ranging between 14.3% in children and 79.3% in HCWs. Seropositivity increased with age among children and HCWs (P ⩽ 0.05). A relatively low seropositivity (64.7%) was observed among young adults and HCWs, suggesting that a high proportion of Sudanese adults remain susceptible. In hospital settings, this result implies a risk of nosocomial infection involving both HCWs and vulnerable patients. The results of this first VZV study in Sudan suggest active virus circulation in different age groups. Especially HCWs at the start of their career might benefit from vaccination, not only to save themselves from herpes zoster and its sequelae, but also to indirectly protect vulnerable patients.

Sex and age as determinants of the seroprevalence of anti-measles IgG among European healthcare workers: A systematic review and meta-analysis

INTRODUCTION

The international literature shows good evidence of a significant rate of measles susceptibility among healthcare workers (HCWs). As such, they are an important public health issue.

METHODS

We conducted a systematic review and meta-analysis to estimate the prevalence of susceptible HCWs in EU/EEA countries and in the UK and to explore the characteristics (sex and age differences) and management of those found to be susceptible.

RESULTS

Nineteen studies were included in the meta-analysis. The prevalence of measles-susceptible HCWs was 13.3% (95 %CI: 10.0-17.0%). In a comparison of serosusceptible female vs. male HCWs, the RR was 0.92 (95 %CI = 0.83-1.03), and in a comparison of age classes (born after vs. before 1980) the RR was 2.78 (95 %CI = 2.20-3.50). The most recent studies proposed the mandatory vaccination of HCWs.

DISCUSSION

According to our meta-analysis, the prevalence of serosusceptible European HCWs is 13%; HCWs born in the post-vaccination era seem to be at higher risk. Healthcare professionals susceptible to measles are a serious epidemiological concern. Greater efforts should therefore be made to identify those who have yet to be vaccinated and actively encourage their vaccination.

Determination of ELISA reactive mumps IgG antibodies in MMR vaccine recipients in comparison with MMR vaccine naive children: A cross sectional study

Background/Aim: Mumps is by vaccine preventable infectious disease characterised by parotitis. In India mumps vaccines are not currently used under National Immunisation Programme (NIP). Waning of vaccine-induced immunity is considered to play a central role in the re-emergence of mumps. The comprehensive data on the seroepidemiology of measles, mumps, and rubella (MMR) as well as studies which compare the antibody titre among mumps vaccine naiveand mumps vaccinated children are lacking. The aim of this study was to estimate and compare mumps specific antibody titre in children with and without MMR vaccine. Methods: In 2019/2020, blood samples were collected from 100 healthy children attending immunisation clinic in Government Medical College Kota and associated J K Lon Maternal and Child care hospital Kota. The samples were investigated for MMR IgG antibodies using ELISA. Results: Out of total 100 children included in the study, 32.27 % vaccinated and 4.83 % non-vaccinated children were positive for mumps IgG antibody in the age group of 6 months to 6 years of age. Children aged 6 to 12 years, vaccinated and non-vaccinated, had 31.57 % and 26.57 % positivity, respectively. The seroprevalence of measles, mumps and rubella antibodies among 50 MMR vaccinated children were 94 %, 64 %, and 96 %, respectively. A high measles and rubella seroprevalences were observed among all children age groups, suggesting an effective control program, while the mumps seroprevalence decreased significantly with age. Conclusion: The maximum vaccine effectiveness against mumps for 2 doses of MMR vaccine is ≈ 96 %. The herd immunity threshold to block mumps virus transmission is ≥ 86 %. In this study only 64 % of the vaccinated children were found to have IgG mumps antibodies. In view of morbidity following mumps infection there is a need to incorporate mumps vaccine along with measles and rubella vaccine in the NIP instead of Mr.