The immune status of migrant populations in Europe and implications for vaccine-preventable disease control: a systematic review and meta-analysis

BACKGROUND

Ensuring vaccination coverage reaches established herd immunity thresholds (HITs) is the cornerstone of any vaccination programme. Diverse migrant populations in European countries have been associated with cases of vaccine-preventable diseases (VPDs) and outbreaks, yet it is not clear to what extent they are an under-immunized group.

METHODS

We did a systematic review and meta-analysis to synthesize peer-reviewed published primary research reporting data on the immune status of migrants in EU/EEA countries, the UK and Switzerland, calculating their pooled immunity coverage for measles, mumps, rubella and diphtheria using random-effects models. We searched on Web of Science, Embase, Global Health and MEDLINE (1 January 2000 to 10 June 2022), with no language restrictions. The protocol is registered with PROSPERO (CRD42018103666).

FINDINGS

Of 1103 abstracts screened, 62 met eligibility criteria, of which 39 were included in the meta-analysis. The meta-analysis included 75 089 migrants, predominantly from outside Europe. Pooled immunity coverage among migrant populations was well below the recommended HIT for diphtheria (n = 7, 57.4% [95% confidence interval (CI): 43.1-71.7%] I2 = 99% vs HIT 83-86%), measles (n = 21, 83.7% [95% CI: 79.2-88.2] I2 = 99% vs HIT 93-95%) and mumps (n = 8, 67.1% [95% CI: 50.6-83.6] I2 = 99% vs HIT 88-93%) and midway for rubella (n = 29, 85.6% [95% CI: 83.1-88.1%] I2 = 99% vs HIT 83-94%), with high heterogeneity across studies.

INTERPRETATION

Migrants in Europe are an under-immunized group for a range of important VPDs, with this study reinforcing the importance of engaging children, adolescents and adults in 'catch-up' vaccination initiatives on arrival for vaccines, doses and boosters they may have missed in their home countries. Co-designing strategies to strengthen catch-up vaccination across the life course in under-immunized groups is an important next step if we are to meet European and global targets for VPD elimination and control and ensure vaccine equity.

Anti-Toxoplasma gondii Antibodies in European Residents: A Systematic Review and Meta-Analysis of Studies Published between 2000 and 2020

Toxoplasmosis has a major impact on animal and public health. Information regarding the seroprevalence of human Toxoplasma gondii infections from a European perspective has not yet been compiled to date. Thus, the present review summarized available resident data from the period 2000-2020. The overall seroprevalence of anti-T. gondii IgG was 32.1%, with great variability between countries (n = 30). The subgroup analysis identified different pooled prevalence data depending on the geographic area (p < 0.0001), target population (p = 0.0147), and serological diagnosis assays used (p = 0.0059). A high heterogeneity (I2 = 100%, p < 0.001; Q = 3.5e+05, d.f. = 135, p < 0.001) and degree of publication bias (Egger's test = 6.14, p < 0.001) were observed among the 134 studies considered. The occurrence of anti-T. gondii IgM, which was reported in 64.7% of studies, reached a pooled seroprevalence of 0.6%. In addition, among the eight main risk factors identified, "contact with soil", "consumption of undercooked beef", and "intake of unwashed vegetables" were the most significantly associated with infections. The fact that one-third of the European population has been exposed to T. gondii justifies extra efforts to harmonize surveillance systems and develop additional risk-factor analyses based on detailed source attribution assessment.

Seroprevalence of Toxoplasma gondii infections in Syrian pregnant refugee women in Turkey

OBJECTIVE

Congenital infections in refugee women have been very rarely studied. The purpose of this study is to investigate the Toxoplasma gondii (T. gondii) seroprevalence in Syrian pregnant refugee women living in Turkey and to discuss the differences with Turkish pregnant women.

STUDY DESIGN

This is a retrospective cohort study including 752 pregnant refugee women and is based on the nine-year data of a reference public hospital in Ankara.

RESULTS

In the study group, T. gondii immunoglobulin G (IgG) and immunoglobulin M (IgM) seropositivity rates were 47 % and 0.4 %, respectively. Compared with a recent study conducted in the same center on Turkish native pregnant women, there was a significant difference in IgG seropositivity and no significant difference in IgM seropositivity.

CONCLUSION

Due to the seroprevalence difference between the indigenous and refugee groups, the Syrian refugee women has to be specifically considered in the prevention of congenital toxoplasmosis infections in Turkey.

Immunity to varicella zoster virus among pregnant women in the Norwegian Mother and Child Cohort Study

Introduction

Infection with varicella zoster virus (VZV) in pregnancy may lead to serious outcomes both for the mother and the newborn. Targeted screening and vaccination of non-immune women during reproductive age could prevent varicella infection in pregnancy. Currently, no universal varicella screening of pregnant women is implemented in Norway, but serological testing in pregnancy is recommended in particular situations. We examined seroprevalence of VZV in a national pregnancy cohort in order to help assess a need for VZV screening of women during reproductive age.

Methods

We determined the susceptibility to VZV and the reliability of self-reported history of VZV infection in the Norwegian obstetric population by using a random sample of 1,184 pregnant women from the Norwegian Mother and Child Cohort study (MoBa). The MoBa study included approximately 95,200 pregnant women in Norway between 1998 and 2009. Blood samples taken at gestational week 17–18 were analysed using a commercial enzyme immunoassay for specific IgG antibodies to Varicella-Zoster virus. Second sample taken at birth was tested if the first sample result was negative or equivocal.

Results

Of the 1,184 pregnant women, 98.6% (n = 1,167) were seropositive, 0.83% (n = 10) remained seronegative, and four women (0.34%) seroconverted during their pregnancy. No significant associations were found between serological status and women’s age at birth, gestational age, women’s country of birth and year of child’s birth. One woman reported prior history of varicella, whereas 143 (12.1%) women reported a household exposure to childhood diseases with fever and rash, of which 25 reported exposure to varicella, of which all were seropositive.

Conclusions

The findings support antenatal screening recommendations in Norway advising testing for VZV in pregnant women with unknown immunity to VZV. Further studies are however needed to better identify target groups for screening and vaccination.

Epidemiological changes in rubella IgG antibody levels detected in antenatal women from a retrospective rubella seroprevalence study

BACKGROUND

Rubella is caused by the rubella virus, a single-stranded RNA virus of the Togaviridae family. The most severe complications of rubella in adult women occur during pregnancy when infection can lead to miscarriage, stillbirth or congenital rubella syndrome. Antenatal rubella susceptibility screening is no longer performed in England, Scotland or Wales but continues in Northern Ireland.

AIM

The aims of this seroprevalence study were to (1) determine amongst women presenting for antenatal care the percentage of women who are rubella susceptible, rubella immune and those with equivocal rubella antibody levels by year of birth and (2) to consider how rubella vaccination resources can best be utilised.

METHODS

A retrospective study was performed analysing all antenatal rubella IgG antibody tests performed between January 2015 and June 2017 inclusive (n = 19,000; excluding duplicate tests). All antenatal women were included regardless of the country of origin and age.

RESULTS

From our analysis, 88.7% (n = 16,868) women had plasma concentrations of anti-rubella IgG > 10 IU/ml. 7.3% of women (n = 1403) had rubella IgG levels between 5 and 9.99 IU/ml, and 2.8% (n = 729) had IgG levels < 5 IU/ml. A decline in rubella immunity in younger women was evident.

CONCLUSIONS

This study has identified an increase in women who are rubella susceptible and women with equivocal rubella antibody levels. International evidence suggests that rubella serology is unreliable and antenatal screening does not confer any benefit to women during their current pregnancy. Consideration should be given to re-direct resources currently utilised for antenatal screening to facilitate the vaccination of pre-pregnancy and postpartum women and also to opportunistically offer vaccination to all women of childbearing age.

Management of suspected primary Toxoplasma gondii infection in pregnant women in Norway: twenty years of experience of amniocentesis in a low-prevalence population

Background

Primary infection with Toxoplasma gondii during pregnancy may pose a threat to the fetus. Women infected prior to conception are unlikely to transmit the parasite to the fetus. If maternal serology indicates a possible primary infection, amniocentesis for toxoplasma PCR analysis is performed and antiparasitic treatment given. However, discriminating between primary and latent infection is challenging and unnecessary amniocenteses may occur. Procedure-related fetal loss after amniocentesis is of concern. The aim of the present study was to determine whether amniocentesis is performed on the correct patients and whether the procedure is safe for this indication.

Methods

Retrospective study analysing data from all singleton pregnancies (n = 346) at Oslo University Hospital undergoing amniocentesis due to suspected maternal primary toxoplasma infection during 1993–2013. Maternal, neonatal and infant data were obtained from clinical hospital records, laboratory records and pregnancy charts. All serum samples were analysed at the Norwegian Institute of Public Health or at the Toxoplasma Reference Laboratory at Oslo University Hospital. The amniocenteses were performed at Oslo University Hospital by experienced personnel. Time of maternal infection was evaluated retrospectively based on serology results.

Results

50% (173) of the women were infected before pregnancy, 23% (80) possibly in pregnancy and 27% (93) were certainly infected during pregnancy. Forty-nine (14%) women seroconverted, 42 (12%) had IgG antibody increase and 255 (74%) women had IgM positivity and low IgG avidity/high dye test titre. Fifteen offspring were infected with toxoplasma, one of them with negative PCR in the amniotic fluid. Median gestational age at amniocentesis was 16.7 gestational weeks (GWs) (Q₁ = 15, Q₃ = 22), with median sample volume 4 ml (Q₁ = 3, Q₃ = 7). Two miscarriages occurred 4 weeks after the procedure, both performed in GW 13. One of these had severe fetal toxoplasma infection.

Conclusions

Half of our study population were infected before pregnancy. In order to reduce the unnecessary amniocenteses we advise confirmatory serology 3 weeks after a suspect result and suggest that the serology is interpreted by dedicated multidisciplinary staff. Amniocentesis is safe and useful as a diagnostic procedure in diagnosing congenital toxoplasma infection when performed after 15 GW.

Are the testing needs of key European populations affected by hepatitis B and hepatitis C being addressed? A scoping review of testing studies in Europe

Aim

To investigate whether or not key populations affected by hepatitis B and hepatitis C are being tested sufficiently for these diseases throughout the European region.

Methods

We searched MEDLINE and EMBASE for studies on HBV and HCV testing in the 53 Member States of the World Health Organization European Region following PRISMA criteria.

Results

136 English-language studies from 24 countries published between January 2007 and June 2013 were found. Most studies took place in 6 countries: France, Germany, Italy, the Netherlands, Turkey, and the United Kingdom. 37 studies (27%) addressed HBV, 46 (34%) HCV, and 53 (39%) both diseases. The largest categories of study populations were people who use drugs (18%) and health care patient populations (17%). Far fewer studies focused on migrants, prison inmates, or men who have sex with men.

Conclusions

The overall evidence base on HBV and HCV testing has considerable gaps in terms of the countries and populations represented and validity of testing uptake data. More research is needed throughout Europe to guide efforts to provide testing to certain key populations.

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.

Varicella-zoster virus susceptibility and primary healthcare consultations in Norway

BACKGROUND

Currently Norway does not recommend universal varicella vaccination for healthy children. This study assessed susceptibility to varicella-zoster virus (VZV) in the Norwegian population for the first time.

METHODS

A national convenience sample of residual sera was tested for anti-VZV IgG by ELISA. We estimated age-specific seropositivity to VZV, controlling for sex and geographical distribution. We assessed differences between the proportions using the chi-square test and multivariable logistic regression. Seroprevalence data were compared to the varicella and herpes zoster-associated consultation rates in patients attending primary healthcare.

RESULTS

Although 73.2 % (n = 1,540) of all samples were positive for VZV, only 11.2 % of samples collected from 1-year-olds were seropositive. There was a sharp increase in the proportion of seropositive in 3- and 5-year-olds (40.2 % and 65.4 %, respectively). By the school entry age of 6 years, 69.8 % of children were seropositive. The age-specific annual consultation rate for varicella in primary healthcare peaked in 1-year-olds, with 2,627 cases per 100,000 population. The profile of varicella-related consultations in primary healthcare mirrored the VZV seropositivity profile. The herpes zoster-related consultations in primary healthcare peaked in people over 70 years of age (702 cases per 100,000 population).

CONCLUSIONS

VZV seroprevalence in Norway was somewhat lower than in some other European countries. The age-specific varicella-related consultation rates in primary healthcare mirrored the age profile of VZV seroprevalence.