Seroprevalence of rubella among urban and rural Bangladeshi women emphasises the need for rubella vaccination of pre-pubertal girls

Rubella Seromarkers and Determinants of Infection among Tanzanian Children and Adolescents in Prevaccination Era: Are We in the Right Track?

Background:

The World health organization advocates assessment of the burden of rubella and congenital rubella syndrome (CRS) by seroepidemiological surveys and surveillance programs in all countries without vaccination programs. Due to scarcity of data in developing countries, this study was conducted to assess the seromakers for natural rubella infection in Tanzania during prevaccination era so as to ascertain the gaps for future research and prevention strategies.

Methods:

A cross-sectional study was conducted between September and October 2014. Indirect enzyme-linked immunosorbent assay was used to detect rubella IgG and IgM antibodies. STATA version 11 was used to perform data analysis.

Results:

Of 723 enrolled participants, 368 (50.8%) and 94 (13%) were positive for specific IgG and IgM rubella antibodies, respectively. On multivariable logistic regression analysis, significant determinants of rubella IgG seropositivity were increase in age (odds ratios [OR]: 1.24, 95% confidence interval [CI]: 1.18–1.29, P < 0.001), low socioeconomic status (SES) (OR: 2.38, 95% CI: 1.1.23–4.50, P = 0.010), and absence of rash (OR: 4.34, 95% CI: 1.1.17–15.3, P = 0.027), while only the presence of rashes was significant determinant of rubella IgM seropositivity (OR: 2.5, 95%; 1.07–5.98, P = 0.034). Significantly higher mean IgG titers were observed in population ≥10 years (P < 0.001), those residing in urban and peri-urban areas (P < 0.001), those from employed mothers (P = 0.018), and those with no current history of fever (P = 0.018).

Conclusions:

The prevalence of specific rubella IgG antibodies in Tanzania is high and is associated with increase in age, absence of rash, and low SES. Results suggest a need to reconsider upper age limit for vaccination campaigns in developing countries. Screening and vaccinating women may be cost-effective campaign to prevent CRS in developing countries.

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.

Using Seroprevalence and Immunisation Coverage Data to Estimate the Global Burden of Congenital Rubella Syndrome, 1996-2010: A Systematic Review

BACKGROUND

The burden of Congenital Rubella Syndrome (CRS) is typically underestimated in routine surveillance. Updated estimates are needed following the recent WHO position paper on rubella and recent GAVI initiatives, funding rubella vaccination in eligible countries. Previous estimates considered the year 1996 and only 78 (developing) countries.

METHODS

We reviewed the literature to identify rubella seroprevalence studies conducted before countries introduced rubella-containing vaccination (RCV). These data and the estimated vaccination coverage in the routine schedule and mass campaigns were incorporated in mathematical models to estimate the CRS incidence in 1996 and 2000-2010 for each country, region and globally.

RESULTS

The estimated CRS decreased in the three regions (Americas, Europe and Eastern Mediterranean) which had introduced widespread RCV by 2010, reaching <2 per 100,000 live births (the Americas and Europe) and 25 (95% CI 4-61) per 100,000 live births (the Eastern Mediterranean). The estimated incidence in 2010 ranged from 90 (95% CI: 46-195) in the Western Pacific, excluding China, to 116 (95% CI: 56-235) and 121 (95% CI: 31-238) per 100,000 live births in Africa and SE Asia respectively. Highest numbers of cases were predicted in Africa (39,000, 95% CI: 18,000-80,000) and SE Asia (49,000, 95% CI: 11,000-97,000). In 2010, 105,000 (95% CI: 54,000-158,000) CRS cases were estimated globally, compared to 119,000 (95% CI: 72,000-169,000) in 1996.

CONCLUSIONS

Whilst falling dramatically in the Americas, Europe and the Eastern Mediterranean after vaccination, the estimated CRS incidence remains high elsewhere. Well-conducted seroprevalence studies can help to improve the reliability of these estimates and monitor the impact of rubella vaccination.

Post-exposure passive immunisation for preventing rubella and congenital rubella syndrome

BACKGROUND

Control of rubella is desired because infection in early pregnancy can result in miscarriage, foetal death or congenital abnormality. Primary studies examining the effectiveness of immunoglobulins for post-exposure prophylaxis of rubella have small sample sizes and varying results. National public health recommendations suggest a degree of effectiveness.

OBJECTIVES

To assess the effectiveness of intramuscular injection or intravenous infusion of polyclonal immunoglobulins of human sera or plasma origin for preventing rubella and congenital rubella syndrome when administered to exposed susceptible people before the onset of disease.

SEARCH METHODS

We searched CENTRAL (2014, Issue 7), MEDLINE (1946 to August week 2, 2014), EMBASE (1974 to August 2014), CINAHL (1981 to August 2014), LILACS (1982 to August 2014) and Web of Science (1955 to August 2014). We searched ClinicalTrials.gov and the World Health Organization International Clinical Trials Registry on 16 October 2014. We searched the reference lists of relevant retrieved reviews and studies and identified national public health guidelines.

SELECTION CRITERIA

For the outcome 'preventing cases of rubella', we included randomised controlled trials (RCTs) and quasi-RCTs. We found several studies addressing this outcome where the design was a controlled clinical trial (CCT) (with exposure to rubella virus controlled by the investigators) but the method of allocation of participants to groups was not reported. We found an alternative report of one of these studies that indicated participants were assigned to groups randomly. We therefore included such studies as meeting criteria for RCTs or quasi-RCTs and undertook sensitivity analyses. For the outcomes, 'congenital rubella infection' and 'congenital rubella syndrome', we included RCTs, quasi-RCTs and prospective controlled (cohort) studies. Participants were necessarily susceptible and exposed to rubella. Polyclonal immunoglobulins derived from human sera or plasma must have been administered intramuscularly or intravenously as the only intervention in at least one group.

DATA COLLECTION AND ANALYSIS

We used the standard methodological procedures expected by The Cochrane Collaboration.

MAIN RESULTS

We included 12 studies (430 participants) in the review: seven RCTs and five CCTs where it was not clear whether participants were randomly allocated to groups. We did not include any unpublished studies. Participants included children and adults of both sexes. Only one study included pregnant women. All studies were conducted in high-income countries.The quality of the 11 studies in the initial meta-analysis was moderate, although we classified no study as having a low risk of bias on all criteria.We included 11 studies in the initial meta-analysis of gamma-globulin (concentrated polyclonal immunoglobulins) versus control (saline or no treatment) for rubella cases. The result favoured the intervention group (risk ratio (RR) 0.61, 95% confidence interval (CI) 0.45 to 0.83) but was heterogenous (Chi² test = 36.59, df = 10 (P value < 0.0001); I² statistic = 73%). Heterogeneity was explained by subgrouping studies according to the estimated volume of gamma-globulin administered per pound of bodyweight and then removing those studies where the intervention was administered more than five days after participant exposure to rubella (post hoc analysis). The test of subgroup differences demonstrated heterogeneity between subgroups according to our protocol definition (P value < 0.1; I² statistic > 60%) and there appeared to be greater effectiveness of the intervention when a greater volume of gamma-globulin was administered ('0.027 to 0.037 ml/lb' RR 1.60 (95% CI 0.57 to 4.52); '0.1 to 0.15 ml/lb' RR 0.53 (95% CI 0.29 to 0.99); '0.2 to 0.5 ml/lb' RR 0.20 (95% CI 0.04 to 1.00)).None of the studies reported the outcome 'congenital rubella infection'. One included study reported on congenital rubella syndrome, with no cases among participants who were fewer than nine weeks pregnant at enrolment and who were randomised to one of two gamma-globulin groups ('high' or 'low' rubella titre). However, the study did not report how congenital rubella syndrome was measured and did not report the length of follow-up according to intervention group. This study did not include a non-treatment group.No included study measured adverse events.

AUTHORS' CONCLUSIONS

Compared to no treatment, polyclonal immunoglobulins seem to be of benefit for preventing rubella. The available evidence suggests that this intervention may be of benefit up to five days after exposure, and that effectiveness is dependent on dose. Considering the attack rate for rubella cases in the control group of the highest volume gamma-globulin subgroup (333 per 1000), the absolute risk reduction (calculated from the RR) for this volume of gamma-globulin was 266 (95% CI 0 to 320) and the number needed to treat to benefit is four (95% CI 3 to incalculable).The included studies did not measure rubella-specific antibodies in the immunoglobulin products used in a standard way and thus estimation of the dose of rubella-specific antibodies in international units administered was not possible. As the concentration of rubella-specific antibodies in today's polyclonal immunoglobulin products may vary from those products used in the studies in the review, the volume required per pound of bodyweight to produce similar results may also vary.There is insufficient evidence to make direct conclusions about the effectiveness of polyclonal immunoglobulins for preventing congenital rubella syndrome. This is an area requiring further research.