Levels of rubella antibody among vaccinated and unvaccinated Portuguese mothers and their newborns

Screening for TORCH Antibodies in Croatian Childbearing-Aged Women, 2014-2023

TORCH infections usually result in mild maternal morbidity, but may cause severe congenital abnormalities. Therefore, it is important to detect maternal infections, monitor the fetus after the disease has been recognized, and define the seronegative women who are at risk of primary infection during pregnancy. From 2014 to 2023, serum samples from 1032 childbearing-aged and pregnant women (16-45 years) were tested for IgM/IgG antibodies to the most common TORCH pathogens: Toxoplasma gondii, rubella virus (RUBV), cytomegalovirus (CMV), and herpes simplex viruses (HSV-1 and HSV-2). The overall IgG seroprevalence rates were 20.1% for T. gondii, 91.3% for RUBV, 70.5% for CMV, 66.8% for HSV-1, and 3.5% for HSV-2. Only HSV-2 seroprevalence was age-related, with a significant progressive increase in seropositivity from 0% in those aged less than 26 years to 9.3% in those older than 40 years. The seroprevalence of T. gondii was higher in residents of suburban/rural areas than in residents of urban areas (27.4% vs. 17.1%). In addition, participants from continental regions were more often toxoplasma-seropositive than those from coastal regions (22.2% vs. 15.3%). HSV-1 seroprevalence was also higher in suburban/rural areas (71.7% vs. 64.7%). Obstetric history was not associated with TORCH seropositivity. Univariate and multivariate risk analysis showed that suburban/rural areas of residence and continental geographic regions were significant risk factors for T. gondii seroprevalence. Furthermore, suburban/rural area of residence was a significant risk factor for HSV-1 seroprevalence, while older age was a significant risk factor for HSV-2 seroprevalence. A declining trend in the seroprevalence of all TORCH pathogens was observed compared to previous Croatian studies (2005-2011). Similarly, the proportion of women simultaneously IgG-seropositive to two or three pathogens decreased over time. The maternal serology before pregnancy could potentially reduce the burden of congenital TORCH infections.

Rubella antibodies in cord blood sera in Portugal: association with maternal age and vaccination status

This study evaluated the impact of maternal vaccination against rubella on the levels of specific rubella IgG (rIgG) in 198 newborn cord sera samples. Detailed maternal vaccination data were available. Specific rIgG was measured using a commercial enzyme immunoassay. Most mothers (78.8%) had been vaccinated against rubella at least once in their lives. In 15 (7.6%) cord sera samples, the concentration of specific rIgG was below 11 IU/ml, which was classified as seronegative. Statistical analysis using multiple logistic regression (n = 198) showed that newborns of mothers born between 1986 and 1995, and those born to unvaccinated mothers, were more likely to be seronegative (odds ratio (ORs) 5.2 and 4.9, respectively, adjusted for sex and gestational age). For vaccinated mothers (n = 156), those born between 1986 and 1995 were more likely to have seronegative newborns (OR 11.5 adjusting for sex, gestational age and time since last vaccination). Mothers of the 15 (7.6%) seronegative newborns might have been susceptible to rubella during pregnancy. Checking the vaccination status therefore recommended.

Global seroprevalence of rubella among pregnant and childbearing age women: a meta-analysis

Background

We conducted a meta-analysis of articles published between January 2000 and July 2016 with the aim of defining the proportion of rubella seronegative women of childbearing age (WCBA), providing the best information available on the seroprevalence of rubella in this population. We selected articles published in the time period between 2000 and 2016. The pooled prevalence of rubella seronegative women was calculated by a fixed effect model and a random effect model, according to the heterogeneity among studies. Studies were sub-grouped by population type (pregnant women and WCBA with no mention of ongoing pregnancy) and by geographic area [World Health Organization (WHO) region]. Sensitivity analysis was performed to assess the stability of results. We found important differences in rubella seronegativity prevalence estimates by WHO Region. About 88% of the studies conducted on pregnant women reported a seronegativity rate >5%. The pooled rubella seronegativity prevalence was 9.3%. When considering population groups, we obtained a seronegativity pooled estimate of 9.4% for pregnant women and of 9.5% for WCBA with no mention of ongoing pregnancy. This meta-analysis shows that the proportion of WCBA who are susceptible to rubella is still high. The figures are worrisome, taking into account that the WHO set at 5% the rubella susceptibility threshold for WCBA.

Persistence of rubella and mumps antibodies, following changes in the recommended age for the second dose of MMR vaccine in Portugal

In Portugal, the recommended age for the second dose of MMR (MMR2) was changed from 10–13 years to 5–6 years for those born in 1994 and afterwards. This study aimed to assess if MMR schedule and time elapsed from the last dose are associated with the concentration of rubella and mumps IgG antibodies. Three Portuguese birth cohorts (convenience samples) were selected for this study (66, 59 and 41 participants born respectively in 1990–1993, 1994–1995 and 2001–2003). Geometric mean concentrations (GMC) for mumps IgG were respectively 36, 30 and 38 RU/ml (P = 0·236) and for rubella IgG were 18, 20 and 17 IU/ml (P = 0·641). For both specific antibodies, no differences were observed with time since MMR2. Receiving MMR2 at 5–6 or 10–13 years was not associated with concentration of both antibodies. The GMC of rubella IgG was lower in males (P = 0·029). Taking into account previous evidence and the logistics needed to change vaccination schedules, it seems reasonable that sustaining very high coverage with two doses of MMR is currently the most pragmatic way to control mumps and rubella rather than any changes to the schedule.

Synthesis of Evidence to Characterize National Measles and Rubella Exposure and Immunization Histories

Population immunity depends on the dynamic levels of immunization coverage that countries achieve over time and any transmission of viruses that occur within the population that induce immunity. In the context of developing a dynamic transmission model for measles and rubella to support analyses of future immunization policy options, we assessed the model inputs required to reproduce past behavior and to provide some confidence about model performance at the national level. We reviewed the data available from the World Health Organization (WHO) and existing measles and rubella literature for evidence of historical reported routine and supplemental immunization activities and reported cases and outbreaks. We constructed model input profiles for 180 WHO member states and three other areas to support disease transmission model development and calibration. The profiles demonstrate the significant variability in immunization strategies used historically by regions and member states and the epidemiological implications of these historical choices. The profiles provide a historical perspective on measles and rubella immunization globally at the national level, and they may help immunization program managers identify existing immunity and/or knowledge gaps.

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.

Serological statuses of pregnant women in an urban Brazilian population before and after the 2008 rubella immunization campaign

BACKGROUND

Vaccinating populations against rubella aims to mitigate viral circulation and to ensure that women of childbearing age are immunized to reduce the incidence of congenital rubella syndrome. This study determined the serological statuses of pregnant women in an urban Brazilian population before and after the national rubella immunization campaign that was undertaken in 2008, and it assessed the socio-demographic factors associated with seronegativity.

METHODS

Pregnant women living in Maceió, Alagoas, Brazil, who participated in a municipal prenatal screening program that involved blood tests for rubella, were assessed between June 2007 and May 2012. Socio-demographic factors associated with seronegativity were assessed, including the year of the blood test, categorized as before or after the 2008 immunization campaign, and the women's birth cohorts, the women's ethnicities, the gestational ages at the first prenatal visit, and the women's districts of residence.

RESULTS

A total of 54,717 capillary blood samples were tested for rubella. The prevalence of pregnant women who were seronegative for rubella declined from 9.4% before the national immunization campaign to 2.8% after the national immunization campaign. Women were more likely to be seronegative for rubella before and after the immunization campaign if they were born between 1990 and 2000 or delayed starting prenatal care.

CONCLUSIONS

The decline in the prevalence of pregnant women who were seronegative for rubella to <5% indicates that the 2008 Brazilian rubella immunization campaign was successful in Maceió.

Persistence of measles antibodies, following changes in the recommended age for the second dose of MMR-vaccine in Portugal

In populations vaccinated with two doses of combined measles-mumps-rubella vaccine (MMR), the serum levels of antibodies against measles depend on the vaccination schedule, time elapsed from the last dose and the area-specific epidemiological situation. Variables measuring "schedule" are age at first and second doses of MMR and intervals derived from that. Changes in vaccination schedules have been made in Portugal. The specific objectives of this study were to measure the association between those potential determinants and the concentration of measles-specific IgG antibodies, after the second dose of MMR. Convenience samples of three Portuguese birth cohorts were selected for this study (41, 66 and 60 born, respectively, in 2001-2003, 1990-1993 and 1994-1995). Geometric mean concentrations (GMC) for measles IgG were, respectively, 934, 251 and 144mIU/ml; p<0.001). Anti-measles-IgG serum concentration decreased with time since last vaccination (waning immunity) and was not influenced by any other component of vaccination schedule, namely age at vaccination with the second dose of MMR. Waning levels of measles antibodies have been observed elsewhere but not as fast as it was observed in Portuguese birth cohorts in this study. Changes in the vaccination schedules might have to be considered in the future.

Antibodies to hepatitis E in Portuguese mothers and their newborns

The high mortality of pregnant women is one of the main features of hepatitis E virus (HEV) infection in endemic countries. With the emergence of genotype 3 HEV in industrialized countries, attention should be given to pregnant women from these regions since the effect of genotype 3 HEV in pregnancy is not yet known. In this study, archived sera dating from 1993 from mothers with no history of traveling to HEV endemic countries and their newborns were tested for anti-HEV IgG antibodies. Four of the 12 maternal sera were positive for IgG anti-HEV, indicating exposure to this virus. Their newborns were also positive, showing higher anti-HEV IgG levels. Overall, these findings demonstrate not only an efficient transplacental transport of anti-HEV IgG, but also circulation of autochthonous HEV in Portugal in the early 1990s.

Rubella antibody screening during pregnancy in an urban area of Northern Italy

Various countries have implemented anti-rubella vaccination campaigns with the main aim of preventing congenital infection. In 2003, Italy joined the European WHO programme for the elimination of congenital rubella and issued a special healthcare plan, one of the objectives of which was to reduce the proportion of rubella-susceptible pregnant women to less than 5% by 2005. The aim of this study was to determine the percentage of seronegative pregnant women after the implementation of this plan. Anti-rubella IgG and IgM antibodies were sought in 2385 pregnant women who attended our hospital for serological screening between 1 July 2008 and 30 June 2010. They included 750 women of foreign origin (31.4%). Eight percent of the women were anti-rubella seronegative: 6.2% of the Italians and 11.7% of the non-Italians. Among the women of foreign origin, the percentage of seronegativity ranged from 5.6% of those coming from Eastern Europe to 17.7% of those coming from Latin America. The level of seropositivity among women of Italian origin is high, although the objective of ensuring less than 5% of susceptible pregnant women has not yet been quite reached in our area. However, particular attention needs to be given to women coming from geographical areas characterised by different epidemiologies and vaccination strategies because the percentage of seronegativity is in some cases double that of Italian women.

Kinetics of maternal antibodies against rubella and varicella in infants

Kinetics of maternal rubella and varicella antibodies in 213 mother-infant pairs are described in a longitudinal study in Belgium. Blood samples are taken at 7 time points (week 36 of pregnancy, birth (cord), 1, 3, 6, 9, and 12 months), and analyzed for anti-rubella IgG and anti-varicella IgG by enzyme linked immunosorbent assay (ELISA). A generalized exponential model is used to analyse maternal antibody decay in infants. Model based, the mean duration of passive immunity is 2.1 months for rubella and 2.4 months for varicella. Infants are susceptible at young age for rubella, a disease with high vaccination coverage, as well as for varicella, an endemic disease in Western Europe.

Rubella seroprevalence in pregnant women in North Thames: estimates based on newborn screening samples

Objectives

Routine screening for rubella susceptibility is recommended in the UK so that women found to be susceptible can be offered immunization in the post partum period. We demonstrate the use of newborn dried blood spot samples linked to routine vital statistics datasets to monitor rubella susceptibility in pregnant women and to investigate maternal characteristics as determinants of rubella seronegativity.

Setting

North Thames region of England (including large parts of inner London).

Methods

Maternally acquired rubella IgG antibody levels were measured in 18882 newborn screening blood spot samples. Latent class regression finite mixture models were used to classify samples as seronegative to rubella. Data on maternal country of birth were available through linkage to birth registration data.

Results

An estimated 2.7% (95% CI 2.4%–3.0%) of newly delivered women in North Thames were found to be seronegative. Mothers born abroad, particularly in Sub-Saharan Africa and South Asia, were more likely to be seronegative than UK-born mothers, with adjusted odds ratios of 4.2 (95% CI 3.1–5.6) and 5.0 (3.8–6.5), respectively. Mothers under 20 years were more likely to be seronegative than those aged 30 to 34.

Conclusion

Our findings highlight the need for vaccination to be targeted specifically at migrant women and their families to ensure that they are protected from rubella in pregnancy and its serious consequences.

Analysis of rubella antibody distribution from newborn dried blood spots using finite mixture models

Eluted dried blood spot specimens from newborn screening, collected in 2004 in North Thames and anonymously linked to birth registration data, were tested for maternally acquired rubella IgG antibody as a proxy for maternal antibody concentration using an enzyme-linked immunosorbent assay. Finite mixture regression models were fitted to the antibody concentrations from 1964 specimens. The Bayesian Information Criterion (BIC) was used as a model selection criterion to avoid over-fitting the number of mixture model components. This allowed investigation of the independent effect of maternal age and maternal country of birth on rubella antibody concentration without dichotomizing the outcome variable using cut-off values set a priori. Mixture models are a highly useful method of analysis in seroprevalence studies of vaccine-preventable infections in which preset cut-off values may overestimate the size of the seronegative population.