Determining rubella immunity in pregnant Alberta women 2009-2012

Immunity of Canadians and risk of epidemics workshop - Conference report

On November 18-19, 2019, the Immunity of Canadians and Risk of Epidemics (iCARE) Network convened a workshop in Toronto, Ontario, Canada. The objectives of the workshop were to raise the profile of sero-epidemiology in Canada, discuss best practice and methodological innovations, and strategize on the future direction of sero-epidemiology work in Canada. In this conference report, we describe the presentations and discussions from the workshop, and comment on the impact of the COVID-19 pandemic on serosurveillance initiatives, both in Canada and abroad.

Rubella seroprevalence among pregnant women in the region of Rabat, Morocco: a cross-sectional study

OBJECTIVES

The aim of the present research is to update data on the seroprevalence of rubella and to identify the associated risk factors among pregnant women in the Rabat region of Morocco in order to take immediate action to monitor the virus.

DESIGN

A cross-sectional study.

SETTING

The study was conducted at Ibn Sina University Hospital and at referral healthcare centres in the region of Rabat.

PARTICIPANTS

A total of 502 pregnant women (mean age 29.7±6.3 years, range 17-44 years) attending the maternity department during 8 months were selected for serological testing.

OUTCOME MEASURES

A structured questionnaire was used to obtain sociodemographic, reproductive and clinical characteristics after obtaining written informed consent. Venous blood samples were collected to determine rubella-specific IgG antibodies using an automated chemiluminescent microparticle immunoassay (ARCHITECT i1000SR and i2000SR, Abbott Diagnostics).

RESULTS

Antirubella IgG antibodies (≥10 IU/mL) were found in 408 (85.9%) pregnant women examined. The rate of susceptibility to rubella virus infection among pregnant women was found to be 14.1%. These protective rates were found to differ significantly between uneducated pregnant women (80.9%) and those with university-level education (95.5%) (p=0.02). Pregnant women in the 17-24, 25-34 and 35-44 years age groups accounted for 92.5%, 85.2% and 82.8%, respectively (p=0.015). Also, IgG seropositivity status was found to differ significantly between multiparous (83.3%) and primiparous (92.5%) pregnant women (p=0.01). None of the other characteristics was significantly associated with rubella infections.

CONCLUSION

Vaccination programmes need to be updated to ensure that campaigns reach their specified goals. Thus, implementing an effective, large-scale screening programme for congenital rubella infection in different regions of Morocco is highly recommended. On the other hand, seronegative pregnant women should be given special preventive care and health education about rubella transmission and congenital rubella syndrome sequelae.

What's in a number? The value of titers as routine proof of immunity for medical students

OBJECTIVES

To assess the guideline concordance of medical school requirements for students' proof-of-immunity in the United States (US) and Canada.

METHODS

National guidelines for healthcare worker proof-of-immunity to measles, mumps, rubella, and varicella were compared to admission requirements for 62 US and 17 Canadian medical schools.

RESULTS

All surveyed schools accepted at least one recommended form of proof-of-immunity, however, contrary to national guidelines, 16% of surveyed US schools asked for a serologic titer, and only 73-79% US schools accepted vaccination as the sole proof-of-immunity.

CONCLUSIONS

The requirement of numerical, non-standardized serologic testing highlights an oversight in medical school admissions documentation. The requirement for quantitative values to demonstrate immunity is not practical from a laboratory standpoint, and is not needed to show individual immunity to these vaccine-preventable diseases. Until a more standardized process is adopted, laboratories will need to provide clear documentation and direction for quantitative titer requests.

Seroprevalence of rubella virus among pregnant women: A 4-year registered-based study from family medicine and obstetric clinics in Saudi Arabia

OBJECTIVES

This study aimed to determine rubella virus infectivity and immune status in pregnant females who visited the family medicine and obstetrics clinics at a large hospital in Saudi Arabia, and to identify the possible predictors of rubella susceptibility.

METHODS

This registered-based, cross-sectional study included pregnant, aged between 18 and 50 years old, who presented for the first antenatal visit between 2017 and 2020. Data on sociodemographic, antenatal characteristics and serological results were collected. Chi-Squared or Fisher's Exact test and t tests were used for bivariate analysis followed by the multivariable logistic regression model.

RESULTS

A total of 4328 pregnant were included in the study. Seroprevalence of rubella immunity was 76.41%. Positive rubella IgM antibody was identified in 1.21% of those who performed the test (17/1409). Odds of susceptibility were decreased with an increase in age (OR = 0.96, 95% CI = 0.95-0.97) and in non-Saudis' (OR = 0.44, 95% CI = 0.36-0.54).

CONCLUSIONS

Approximately 24% of pregnant were susceptible to rubella virus infections in this study. Screening females of child-bearing age and reimmunisation of susceptible cases before pregnancy are suggested. Further studies to investigate the impact of applying this policy in premarital screening are recommended.

Respiratory Failure and Death in Vulnerable Premature Children With Lower Respiratory Tract Illness

Background

Efforts to better understand the risk factors associated with respiratory failure (RF) and fatal lower respiratory tract infection (LRTI) in premature children in developing countries are necessary to elaborate evidenced-based preventive interventions. We aim to characterize the burden of respiratory syncytial virus (RSV) and human metapneumovirus (hMPV) LRTI in premature children and determine risk factors for RF and fatal illness in a vulnerable population.

Methods

This is a prospective, population-based, cross-sectional study. Subjects with severe LRTI were enrolled during respiratory season. Risk factors for RF and death in premature infants were investigated.

Results

A total of 664 premature children participated. Infant’s hospitalization rate due to LRTI was 82.6/1000 (95% confidence interval [CI], 68.6–96.7/1000). Infant’s RSV and hMPV rates were 40.9/1000 (95% CI, 36.3–45.6/1000) and 6.6/1000 (95% CI, 3.9–9.2/1000), respectively. The RF rate was 8.2/1000 (95% CI, 4.9–11.5/1000). The LRTI mortality was 2.2/1000 (95% CI, 0.7–3.7/1000); for RSV, the rate was 0.8/1000 (95% CI, 0–1.7/1000) with a case-fatality ratio of 1.8%. Never breastfeeding, malnutrition, younger than 6 months, congenital heart disease, and lower hematocrit were risk factors for RF. Experiencing pneumonia, pneumothorax, sepsis, or apnea were clinical determinants of poor outcomes.

Conclusions

Premature children under 2 years old in vulnerable environments experience RF and death more often than term counterparts. Modifiable risk factors associated with poor outcomes should prompt evidence-based interventions.

Seroprevalences of antibodies against pertussis, diphtheria, tetanus, measles, mumps and rubella: A cross-sectional study in children following vaccination procedure in Guangzhou, China

This study investigated the concentrations and seroprevalence of immunoglobulin G (IgG) antibodies against pertussis, diphtheria, tetanus, measles, mumps and rubella among children in Guangzhou, China. We conducted a cross-sectional study focusing on the post-vaccination immune statuses of children on scheduled immunisation. Human IgG antibody against six diseases were measured using commercial enzyme-linked immunosorbent assay kits. Of 620 subjects, the male-to-female ratio was 2.04 (416/204). Seroprevalence (81.97% vs 90.20%) and IgG concentrations (686.55 IU/mL vs 884.26 IU/mL, P < 0.05) for measles, tetanus (0.94 IU/mL vs 1.21 IU/mL) and rubella (34.33 IU/mL vs 47.37 IU/mL) were all higher in females. No differences based on sex were observed in the seroprevalence and IgG concentrations for anti-pertussis antibodies, anti-diphtheria antibodies and anti-mumps. Slight increase in seroprevalence and IgG concentration occurred with anti-pertussis antibodies after primary and booster vaccinations (from 0.00% [1 m], 5.45% [6 m], to 17.14% [1.5 yr]; and from 8.57% [5 yr] to 15.79% [6 yr]). Although no booster vaccination was given after age 6 yr, the seroprevalence and IgG concentration for anti-pertussis antibodies remained relatively stable. For diphtheria, tetanus, measles and rubella, seroprevalence reached their peaks after the primary and first booster vaccination. A plateau occurred after age 1.5 yr with a declining trend in subjects >8-10 yr. The IgG concentrations of these 4 pathogens showed a dramatic increase after primary vaccination, with steadily declining trends thereafter. For mumps, subjects showed increased seroprevalence and IgG concentration after the primary mumps-containing vaccination in 1.5-yr-olds (from 7.14% to 57.14%; 52.13 IU/mL to 214.18 IU/mL); however, following that low seroprevalence levels (from 42.86% to 80.00%) were observed. The post-vaccination immune statuses against diphtheria, tetanus, measles and rubella were relatively satisfactory, compared to those against pertussis and mumps. Booster vaccination against pertussis and mumps at appropriate time should be considered.

Recent trends in seroprevalence of rubella in Korean women of childbearing age: a cross-sectional study

OBJECTIVES

The aim of this study was to investigate the immunity against rubella using the serological status of rubella-specific IgG antibodies (antirubella IgG) in Korean women of childbearing age (15-49 years).

DESIGN

Retrospective cross-sectional study.

SETTING

Population-based cross-sectional study in South Korea.

PARTICIPANTS

Between January 2010 and December 2017, test results from Korean women aged 15-49 years who had visited an obstetric private clinic (nationwide institutions) and had requested rubella-specific IgG antibody tests from Green Cross Laboratories were obtained from the laboratory information system.

RESULTS

Between 2010 and 2017, antirubella IgG test results from 328 426 Korean women aged 15-49 years who had visited private obstetric clinics (1438 institutions nationwide) were retrospectively analysed by tested year, age, cohort and geographic regions. Over the 8-year study period, the rate of unimmunised women ranged from 7.8% to 9.7%. Multivariable-adjusted logistic regression models showed that the odds of being immune to rubella (positive and equivocal results of antirubella IgG test) were lower in 2017 compared with 2010, in women in their 40s, in a pre-catch-up cohort and in women living in Incheon, Busan, South Gyeongsang, North and South Jeolla and Jeju provinces (p<0.0001).

CONCLUSIONS

In consideration of the factors associated with prevalence of women unimmunised to rubella, future public health efforts should be focused on catch-up activities. The results of this study could be used to strengthen disease control and prevent rubella, including a nationwide immunisation programme.

No. 368-RUBELLA IN PREGNANCY

OBJECTIVE

To review the epidemiology, natural history, evaluation, and prevention of rubella infection during pregnancy. This will aid obstetric care providers in counseling their patients regarding potentially devastating effects on the developing fetus and the importance of vaccinating susceptible women as appropriate.

OUTCOMES

Outcomes evaluated include fetal rubella infection, maternal seroconversion and response to rubella-containing vaccines.

EVIDENCE

Medline, PubMed, EMBASE, and Cochrane databases were searched for articles in English on subjects related to rubella infection during pregnancy betweenn 1985 and 2017. Results were restricted to systematic reviews, randomized controlled trials/controlled clinical trials, and observational studies. Other (unpublished) literature was identified through searching the websites of health technology assessment and health technology assessment-related agencies, clinical practice guideline collections, clinical trial registries, and national and international medical specialty societies.

VALUATION METHODS

The quality of the evidence is rated using the criteria described in the Report of the Canadian Task Force on Preventive Health Care (Table 1). Recommendations for practice are ranked according to the method described in this Report.

GUIDELINE UPDATE

The guideline will be reviewed 5 years after publication to decide if an update is required. However, if important new evidence is published prior to the 5-year cycle, the review process may be accelerated for a more rapid update of some recommendations SPONSOR: Society of Obstetricians and Gynaecologists of Canada.

RECOMMENDATIONS

Overview of a Provincial Prenatal Communicable Disease Screening Program: 2002-2016

OBJECTIVE

This study sought to provide a 14-year overview of serological results from a provincial prenatal screening program.

METHODS

Prenatal screening data from August 2002 to December 2016 were extracted from the Alberta Public Health Laboratory (ProvLab) Information system. Data were analyzed by year, communicable disease marker, test result, and maternal age category. The age-stratified proportion of seropositive results for hepatitis B virus, human immunodeficiency virus, and syphilis was determined, and the proportion of seronegative results was determined for rubella and varicella. The Mann Kendall Trend Test was performed to identify significant temporal trends in the results (Canadian Task Force Classification II-2).

RESULTS

In total 821 910 prenatal specimens were examined. Overall, the proportion of prenatal specimens positive for hepatitis B virus showed a slight statistically significant upward trend from 0.50% in 2003 to 0.58% in 2016 (P = 0.03). The proportion of positive human immunodeficiency virus prenatal specimens showed no significant trend over the study period. The proportion of positive syphilis specimens increased from 2006 to 2008 (0.07% to 0.21%; P < 0.0001) and stayed relatively constant until a decrease began in 2015. The proportion of seronegative specimens for varicella and rubella showed a significant upward trend of 0.48% per year (P < 0.01) and 0.88% per year (P < 0.01), respectively.

CONCLUSION

The Alberta Prenatal Screening Program for Selected Communicable Diseases presents a unique data set that allows us to look at screening results on a provincial level. Trends in results are reflective of communicable disease trends in the general population and should be monitored for effective infectious disease management of the maternal and newborn population.

Response to third rubella vaccine dose

Limited data exist on the immunogenicity of a third dose of the measles, mumps, and rubella vaccine (MMR). In this study, our aim was to evaluate the long-term rubella immunogenicity afforded by two childhood MMR doses of the Norwegian vaccination program in a cohort of conscripts and to determine the effect of an additional dose of MMR vaccine, in order to inform vaccination policy. Blood samples from Norwegian conscripts (n = 495) taken both before and eight months after administration of a dose of MMR vaccine were tested using an enzyme immunoassay to measure anti-rubella IgG. Concentrations <5 IU/mL were regarded as negative, 5.0-9.9 IU/mL as equivocal, and ≥10 IU/mL as positive. Overall, the seropositivity before vaccination was 84.6%, and 99.0% of the conscripts had anti-rubella IgG concentrations ≥5 IU/mL. The seropositivity after vaccination was 94.5%, and 99.8% of the conscripts had antibody concentrations ≥5 IU/mL. The geometrical mean IgG concentrations increased from 21.4 IU/mL before vaccination to 28.9 IU/mL after. Four out of five conscripts, with seronegative concentrations before administrations of an additional MMR dose, had equivocal or seropositive results following vaccination. The cohort of young adults in Norway, which was eligible for two childhood MMR doses, was protected against rubella, and efforts should be made to maintain high vaccine coverage to ensure immunity in the future. A third dose of MMR administered in early adulthood led to an increase in the antibody concentration in our cohort and seroconversion for the majority of seronegative persons.

How to determine protective immunity in the post-vaccine era

The ability to determine an individual's susceptibility to infection relies heavily on the assay used, and the ability to correlate results of the assay to a clinical interpretation. Current rubella immunity screening methods identify total rubella IgG antibodies circulating in the serum, however both humoral and cell mediated immune responses have been shown to contribute to protection from infection. Therefore, antibody screening assays may under-estimate immunity in some populations. In fact, waning antibody titers over time in a large prenatal population were recently documented in North America, and the trend has been echoed in other countries that have achieved elimination through universal rubella vaccination. Despite decreasing antibody titers, the number of acute rubella cases has not increased in these populations, suggesting that the lower antibody levels may still be protective. Based on the changing epidemiology in universally vaccinated populations, it may be time to reassess the level of antibody that indicates immunity to rubella infection.

Screening for potential susceptibility to rubella in an antenatal population: A multivariate analysis

Rubella causes disease in the fetus. Immunity to rubella is therefore, routinely screened in pregnant women. In this retrospective observational study, we assessed the levels of potential susceptibility to rubella in the population of a north London antenatal clinic. Risk factors for potential susceptibility to rubella and changes in potential susceptibility to rubella over time were studied. Almost all women were screened for potential susceptibility to rubella (99.8%). The majority were predicted to be immune (96.8%). Women booking in later years within the study period showed higher levels of potential susceptibility to rubella. Booking during each subsequent year in the study gave women an odds ratio of 0.91 (CI:0.84, 0.98, P = 0.009) of being predicted to have immunity against rubella. Age was associated with predicted immunity to rubella, with a 5.1% (CI:3.3%, 6.9%, P < 0.001) increased likelihood for every year older. Previous pregnancy was predictive of immunity against rubella with an odds ratio of 1.41 (CI 1.21, 1.61, P = 0.001). Those from a non-white ethnicity were less likely to have antibodies predictive of immunity (OR: 0.730, CI: 0.581, 0.879 P < 0.001). Country of birth was associated with differences in potential susceptibility, with those being born outside of the British Isles having an odds ratio for predicted immunity of 0.63 (CI:0.35,0.91, P = 0.001). Being born in a high-risk country for rubella non-immunity was also a risk factor, giving an odds ratio of predicted immunity to rubella of 0.55 (CI:0.32, 0.77, P < 0.001).

Seroprevalence of rubella antibodies and determinants of susceptibility to rubella in a cohort of pregnant women in Canada, 2008-2011

Long term control of rubella and congenital rubella syndrome relies on high population-level immunity against rubella, particularly among women of childbearing age. In Canada, all pregnant women should be screened so that susceptible new mothers can be offered vaccination for rubella before discharge. This study was undertaken to estimate rubella susceptibility in a cohort of pregnant women in Canada and to identify associated socio-economic and demographic factors. Biobanked plasma samples were obtained from the Maternal-Infant Research on Environmental Chemicals (MIREC) study, in which pregnant women were recruited between 2008 and 2011. Socio-demographic characteristics and obstetric histories were collected. Second trimester plasma samples (n=1,752) were tested for rubella-specific IgG using an in-house enzyme-linked immunosorbent assay. The percentage of women with IgG titers <5IU/mL, 5-10IU/mL, and ≥10IU/mL were 2.3%, 10.1%, and 87.6%, respectively. Rates of seronegativity, defined as <5IU/mL, were 3.1% in women who had no previous live birth and 1.6% in women who had given birth previously. Among the latter group, seronegativity was higher in women with high school education or less (adjusted OR (aOR) 5.93, 95% CI 2.08-16.96) or with a college or trade school diploma (aOR 3.82, 95% CI 1.45-10.12), compared to university graduates, and those born outside Canada (aOR 2.60, 95% CI 1.07-6.31). In conclusion, a large majority of pregnant women were found to be immune to rubella. Further research is needed to understand inequalities in vaccine uptake or access, and more effort is needed to promote catch-up measles-mumps-rubella vaccination among socioeconomically disadvantaged and immigrant women of childbearing age.

Rubella Immunity in Pregnant Native Taiwanese and Immigrants from Asian Countries

Vaccination is considered the most effective method to prevent rubella spread and congenital rubella syndrome (CRS). The aim of the present study was to investigate the rubella immunity among native and immigrant pregnant women in Taiwan. From 2000 to 2014, a total of 16,879 pregnant women who received routine prenatal examinations were recruited in this study. The rubella IgG antibodies were assayed using a microparticle enzyme immunoassay or chemiluminescent microparticle immunoassay. Subjects were categorized by nationality and subcategorized by specific periods of time for comparison. The rubella susceptibility was 12.7% in total, 11.1% in Taiwanese and 20.3% in immigrant population from 2000 to 2014. Among the immigrant women, those from Vietnam had the highest susceptibility (22.3%) and those from Thailand had the lowest susceptibility (3.8%). The immigrant women from Vietnam and China showed a significantly higher susceptibility compared with the native Taiwanese women in which the odds ratio was 2.30 (95% confidence interval [CI]: 2.04-2.60), 1.96 (95% CI: 1.59-2.41), respectively (P < 0.001). It meant that immigrants from Vietnam and China had a higher likelihood of rubella susceptibility and related CRS sequela than native women. From 2000-2004 to 2010-2014 cohort, there was no obvious change in rubella susceptibility in native women, which varied between 10.0% and 11.9%. However, there was a decreasing trend of rubella susceptibility in the immigrant women overall, from 24.5% to 11.5% (P < 0.001). To eliminate congenital rubella in Taiwan, additional catch-up immunization strategies are needed.

Vaccination in secondary school students expedites rubella control and prevents congenital rubella syndrome

Background

In order to control the spread of rubella and reduce the risk for congenital rubella syndrome, an additional rubella vaccination program was set up for all secondary school students since 2008 in Zhejiang, China.

Methods

We conducted a descriptive analysis of rubella incidence among different age groups from 2005 to 2015 and a serosurvey of female subjects aged 15–39 years to understand the possible effects of this immunization program.

Results

The average annual rubella incidence rate had decreased from 15.86 per 100,000 population (2005–2007) to 0.75 per 100,000 population (2013–2015) in Zhejiang. The decrease in the rate of rubella incidence in girls aged 15–19 years was more accelerated (from 138.30 to 0.34 per 100,000) than in the total population during 2008–2015 (from 32.20 to 0.46 per 100,000). Of 1225 female subjects in the serosurvey, 256 (20.9%) were not immune to rubella. The proportion of subjects immune to rubella was significantly different among different age groups (Wald χ2 = 22.19, p = 0.000), and subjects aged 15–19 years old had the highest immunity (88.0%). Rubella antibody levels were significantly lower in women aged 25–30 years with 26.7% of them not immune, followed by the group aged 20–24 years (25.0%) and 30–35 years (24.5%).

Conclusions

Rubella vaccine included in the Expanded Program on Immunization together with vaccination activities for secondary school students can help in rubella control, particularly in targeted age groups in the program. Seroprevalence of antibodies to the rubella virus amongst the female population within childbearing age in Zhejiang, China, is still too low to provide immunity. In addition to vaccination programs in the secondary schools, rubella vaccination should also be encouraged in women of childbearing age, which can be done effectively combined with pre-marital examination in China.

Economic impact of switching rubella IgG methodologies to the prenatal public health program in Alberta

BACKGROUND

Despite widespread use of a universal rubella standard, variability in rubella antibody titre can be observed between assays, particularly at the low end of the linear range.

OBJECTIVES

Here, we investigate the impact of a methodology change for rubella IgG from the Abbott AXSYM to the Abbott Architect in a comprehensive prenatal screening program in the Canadian province of Alberta.

STUDY DESIGN

51,815 specimens (21,399 tested by AxSYM and 30,416 tested by Architect) submitted for routine prenatal screening between January 2006 and December 2012 from women who lived in Alberta after the universal childhood immunization programme for rubella was implemented, and whose immunization records were available, were included in the study.

RESULTS

Prenatal samples tested by AxSYM for rubella IgG were approximately 30% higher than those reported by Architect. Among individuals who had tests across multiple pregnancies, the change in test platform led to an additional 7% of women who initially tested positive, becoming non-positive (i.e. negative or indeterminate) in their subsequent tests. The tendency of the Architect IgG assay to report lower quantitative values was demonstrated across all birth cohorts and vaccination status, and resulted in an additional 2800 women requiring vaccination between 2010 and 2012 with an estimated cost of $38,500.

CONCLUSION

The change in rubella IgG screening assay resulted in a significant increase in the number of women who required post partum vaccination and Public Health follow-up.

Rubella Immune Status in Pregnant Women in a Northern Mexican City

BACKGROUND

The seroepidemiology of rubella virus infection in pregnant women in northern Mexico is largely unknown. We sought to determine the seroprevalence of rubella virus infection in pregnant women in the northern Mexican city of Durango, Mexico. Seroprevalence association with the socio-demographic, clinical and behavioral characteristics of the pregnant women was also investigated.

METHODS

Through a cross-sectional study, we determined the seroprevalence of IgG and IgM anti-rubella virus in 279 pregnant women (mean age 29.17 ± 5.96 years; range 15 - 43 years) attending in a clinic of family medicine using enzyme-linked fluorescent assays. A questionnaire was used to obtain the socio-demographic, clinical and behavioral characteristics of the pregnant women. The association of rubella seropositivity and characteristics of the women was assessed by bivariate and multivariate analyses.

RESULTS

Anti-rubella IgG antibodies (≥ 15 IU/mL) were found in 271 (97.1%) of the 279 pregnant women examined. None of the 279 pregnant women were positive for anti-rubella IgM antibodies. Multivariate analysis of socio-demographic, clinical and behavioral variables showed that seroreactivity to rubella virus was positively associated with national trips (OR = 7.39; 95% CI: 1.41 - 38.78; P = 0.01), and negatively associated with age (OR = 0.26; 95% CI: 0.06 - 0.99; P = 0.04).

CONCLUSIONS

Rate of rubella immunity in pregnant women in the northern Mexican city of Durango is high. However, nearly 3% of pregnant women are susceptible to rubella in our setting. Risk factors associated with rubella seropositivity found in this study may be useful for optimal design of preventive measures against rubella and its sequelae.