The European Journal of Public Health Advance Access published online on April 18, 2007
The European Journal of Public Health, doi:10.1093/eurpub/ckm034
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Rubella immune status of indigenous and immigrant pregnant women in Catalonia, Spain
Angela Dominguez1,3, Pere Plans1, Jordi Espuñes1, Josep Costa2, Nuria Torner1, Neus Cardeñosa1, Antoni Plasencia1 and Lluís Salleras3
1 Directorate of Public Health, Generalitat of Catalonia, Barcelona, Spain
2 Department of Microbiology. Hospital Clinic, Barcelona, Spain
3 Department of Public Health. University of Barcelona, Barcelona, Spain
Correspondence: Angela Dominguez, Directorate of Public Health, Department of Health, Generalitat of Catalonia, Travessera de les Corts 131–159, 08029 Barcelona, Spain, tel: 34 93 227 2951, e-mail: angela.dominguez{at}gencat.net
Received October 19, 2005, accepted March 19, 2007
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Abstract |
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Background: The objective of the study was to determine the prevalence of rubella antibodies in representative samples of pregnant women in Catalonia. Methods: A representative sample of pregnant women in Catalonia was obtained by random sampling by clusters (hospitals with maternity units) stratified by provinces. Blood was obtained from the umbilical cord at childbirth in 1538 women (of whom 308 were immigrants) and was tested for rubella antibodies by ELISA (Enzime-linked immunosorbent assay). Results: The global prevalence of antibodies was 93.4% [95% confidence interval (CI): 93.3–93.5] and was significantly higher in indigenous women (94.9;95%CI:93.3–95.9) compared with immigrants [89.0; 95%CI: 85.5–92.5 (P < 0. 0001)] with crude Odds ratio (OR) of 2.15 (95%CI: 1.40–3.32).The prevalence was higher in women living in rural habitats (97%) and those in higher social classes (96.3%); OR 2.54 (95%CI: 1.22–5.30) and 2.17 (95%CI: 1.24–3.81), respectively. Conclusion: Fertile female immigrants from countries with no vaccination or where vaccination coverage is low should be actively approached for vaccination to reduce the risk of infection and congenital rubella.
Keywords: immigrant, pregnant women, rubella, vaccination
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Introduction |
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Rubella is a febrile exanthematic disease that is benign in children and causes arthralgia and less frequently arthritis in adults. Although rare, complications such as thrombocytopaenia, encephalitis, Guillain–Barré syndrome, myocarditis and pericarditis may appear in adults.1 The serious consequences of the infection occur in newborns, particularly if infection of the mother occurs during the first quarter of gestation, in the form of congenital rubella syndrome (CRS) which may include miscarriage and severe alterations in the growth and development of the foetus, microcephaly, cataracts, hepatosplenomegaly, heart disease, deafness, meningitis and other disorders.
Given the availability of a highly efficacious vaccine, in 1998, the European Regional Committee of the WHO, established the objective of reducing the incidence of CRS to <1/100 000 live births by 2010. The number of European countries that administer two doses of rubella vaccine has increased considerably in recent years, although coverage is still suboptimal in some countries.2 Finland, which introduced a vaccination policy in 1982, eliminated CRS in 1986 and post-natal rubella in 1996.3
In Catalonia, an authonomous region in the northeast of Spain with nearly 7 million inhabitants, rubella vaccination at age 11 began in 1978, with a policy of double vaccination with the measles mumps and rubella vaccine (MMR) at 12 months and the rubella vaccine at 11 years from 1981. Vaccination of all children with the MMR at 15 months and 11 years was introduced in 1988. Given the good results obtained with the measles elimination programme, with the last indigenous outbreak taking place in 1999, the Autonomous Government of Catalonia, in 2002, established a programme for the elimination of indigenous post-natal and congenital rubella before the end of 2005. However, the high vaccination coverage in children reduces the risk of infection of seronegative women but does not eliminate it completely.1 Thus, in order to eliminate congenital rubella, surveillance of the immune status of fertile women against the rubella virus is vital. The objective of this study was to determine the prevalence of rubella antibodies in a representative sample of pregnant women in Catalonia in order to identify risk groups with a low prevalence and to advise on targeted vaccination.
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Selection of the sample
A representative sample of pregnant women in Catalonia was obtained by random sampling by clusters (hospitals with maternity units) stratified by provinces. The sampling was carried out in two stages. Firstly, 27 hospitals were selected randomly from a total of 87 hospitals with obstetric wards and a total of 13 089 deliveries during the study period. Secondly, all pregnant women who gave birth in the selected hospitals during July and August 2004 were selected. In each hospital, the women were informed of the objectives of the study and asked to participate. Informed consent was obtained for the taking of blood samples and the collection of personal data using a questionnaire.
Questionnaire
All participants, after delivery, completed a questionnaire which collected personal data, place of birth, age, place of residence (rural if <10 000 inhabitants and urban if 
10 000 inhabitants), educational level, socioeconomic level and rubella vaccination history. The variable immigration was defined according to the place of birth. Immigrants were considered as women who had not been born in Catalonia or another region of Spain. The socioeconomic level was determined by the profession, classifying all participants in two socioeconomic levels (high: I–III; low: IV–VI), according to the English classification of the Office of Population Census and Surveys. Written informed consent was obtained from each subject included in the study.
Serological analysis
Blood samples were obtained from the umbilical cord at birth. The samples were left to coagulate at room temperature and serum was obtained by centrifugation. An aliquot of the serum obtained was frozen at –20°C until serological analysis, which was carried out in the microbiology laboratory of the Hospital Clinic of Barcelona. Rubella IgG antibodies were determined by ELISA [ETI-RUBEK-G PLUS (Diasorin, 13040 Saluggia-Vercelli, Italy)].
Statistical analysis
The prevalence of rubella antibodies and the prevalence Odds Ratio (OR) were calculated for the different socioeconomic groups. The Chi-square test was used to study the differences. The level of statistical significance was established at P < 0.05. The 95% confidence intervals (CI) and the OR of the prevalences were calculated. The 95% CI of the OR were calculated by Cornfield's method. The statistically significant OR in the bivariate analysis were adjusted by multiple logistic regression analysis (SPSS statistical programme) to determine the variables independently associated with the presence of antibodies. A logistic regression analysis was carried out to determine the significant variables in the bivariate analysis that were independently associated with the prevalence of antibodies. All statistically significant sociodemographic variables, as well as age and a history of vaccination were included.
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Results |
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A total of 1538 women participated in the study. The distribution of the sample studied was similar to the distribution of the Catalan population with respect to sociodemographic variables according to data from the Statistics Institute of Catalonia for the year 2003 (table 1). The distribution of the sample according to place of birth was: 1058 (68.8%) born in Catalonia, 172 (11.2%) born in another region of Spain, 60 (3.9%) in another European country, 30 (2%) in Asia, 85 (5.5%) in Africa, 131 (8.5%) in America and 2 (0.1%) in Oceania. A total of 1437 samples were positive for rubella antibodies, a prevalence of 93.4% (95%CI: 93.3–93.5) (table 2). In immigrant women, the prevalence was 89% (95%CI: 85.5–92.5), lower than the 94.6% (95%CI: 93.3–95.9) found in indigenous women. The prevalence of antibodies in indigenous and immigrant women according to the study variables is shown in table 3. A history of vaccination was reported in 58% of indigenous women, compared with only 38% in immigrants. In women aged <25 years the prevalence of antibodies was 89.9% (95%CI: 86.5–93.3), lower than other age groups, although the differences were only statistically significant (P < 0.01) with respect to the 25–29 years age group, which had a prevalence of 95.4% (95%CI: 93.3–97.5), while the 30–34 and the >34 years age groups had a prevalence of 94.1% (95%CI: 92.1–96.1) and 93.2% (95%CI: 90.4–96.0), respectively. The prevalence of antibodies was greater in indigenous women, in residents of rural habitats, and in women belonging to the higher social classes (I–III), with crude OR of 2.15 (95%CI: 1.40–3.32), 2.54 (95%CI: 1.22–5.30) and 2.17 (95%CI: 1.24–3.81), respectively. In women with a history of rubella vaccination the prevalence of antibodies was higher than in non-vaccinated women (94.8% versus 91.8%, P = 0.019) (table 4). The results of the logistic regression analysis showed that indigenous status, rural habitat and high social class were independently associated with the prevalence of antibodies, with adjusted Odds Ratios (aOR) of 1.75, 2.33 and 1.90, respectively.
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Discussion |
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This study found that 6.6% of fertile women in Catalonia are susceptible to rubella infection. The only seroprevalence survey carried out in Catalonia in similar population dates from 1985 and found a global prevalence of antibodies of 97.5%. The authors concluded that, given the low vaccination coverage, this prevalence was due more to circulation of the virus than to vaccination.4
The main objective of rubella vaccination programmes is to prevent congenital rubella syndrome, i.e. to avoid infections during pregnancy. To reach this objective, two not incompatible strategies have been formulated: (i) to vaccinate all fertile women; (ii) to obtain vaccination coverage >95% in children.
The first strategy is followed mainly by the United Kingdom, where screening of pregnant women in order to offer postpartum vaccination to susceptible women is widespread.5 The second strategy has been implemented by countries such as Finland and Sweden, where, after selectively vaccinating girls from 1975, double universal vaccination with the MMR was introduced in 1982.3,6
In Catalonia, the main strategy has been to ensure high coverage by two doses of vaccine in children. According to a recent study carried out in a representative sample of children, coverage of the first dose of MMR was 98% in indigenous children and 93% in the children of immigrants.7 The last indigenous case of congenital rubella occurred in 1991 and a single imported case occurred in 2004.
The present study found that susceptibility to rubella infection is greater in immigrant women (11%) than in indigenous women (5.4%). Vaccination coverage was 58% in indigenous women and 38% in immigrant women. The gap between these figures and the prevalence of antibodies could be explained by circulation of the wild virus or by a lack of vaccine certification. Thus, the validity of this coverage may be questioned, because it is probable that some vaccinated women did not remember having been vaccinated or did not have the correct documentation, as suggested by other reports both on rubella8,9 and on other vaccine preventable diseases.10 The global prevalence of antibodies found in the present study is somewhat lower than that found by studies in 2001 and 2002 in two other Spanish regions.11,12 A more recent study in Madrid13 found prevalences of 96.7% in indigenous women and 89.3% in immigrants, very similar to the results in Catalonia.
Of the 52 member states of the European Region of the World Health Organization, although there are slight differences in timing, only Tajikistan and Turkmenistan do not include rubella in their vaccination schedules.14 In countries with established rubella vaccination programmes, the susceptibility of women is under 2% in the United Kingdom and Holland and is similar to Catalonia in Germany and Italy.15 In France, in women aged 15–19 years, the level of susceptibility of 12% is greater than the 10.1% found in Catalonia in women aged <25 years of age.15 In the present study, Latin-American women had a greater susceptibility, probably because in their countries of origin there is either no vaccination or coverage is very low.8 Yamamoto et al.16 found that, in some areas of Mexico, the susceptibility was 62%, with a range of 29–76%.
In Spain, Latin-American immigration is significant and outbreaks which selectively affect this group have been reported.17,18 Susceptibility in immigrants from other countries varies enormously and is higher in women from rural, isolated areas where the virus only circulates during epidemic periods.19 Cutts et al.20 carried out a study in developing countries and found levels of susceptibility in pregnant women ranging from 4% in some regions of Oman to 64% in rural areas of Panama and 68% in Trinidad and Tobago. In our study, the prevalence of antibodies was lower in women living in urban compared with rural habitats, because immigrant women tend to live in larger cities, where the possibilities of finding work and services are greater.1 Finally, we found that higher social class was associated positively with the prevalence of antibodies, results similar to those of Gutiérrez et al.21
In conclusion, the level of susceptibility to rubella virus infection in Catalonia in fertile immigrant women is suboptimal in relation to the target of eliminating congenital rubella. This indicates the need to use any contact between this group of women and the health services to offer them vaccination whenever a vaccination history cannot be provided, and also to systematically vaccinate fertile immigrant women from countries without vaccination or with low coverage.22
The first policy has been suggested by various authors8,23 and is included in the guide for the elimination of rubella in Catalonia,24 although compliance seems to be low and suggests that greater effort is required. Schluter et al.8 report that, among the cases of CRS studied, in 81% the opportunity to vaccinate postpartum had been lost. The second policy is not easy to achieve, but we agree with Tookey et al.25 that it is essential to avoid outbreaks of the disease such as those that have occurred both in Spain (Catalonia and Madrid)17,18 and in other countries.9 Danovaro et al.9 found that although the prevalence of antibodies before an outbreak was 87%, this level was not sufficient to avoid the outbreak. Biologically, rubella may be eliminated if there is political consensus and the necessary resources are mobilized.26 The need to identify susceptible fertile women is unquestionable.15,27 In addition, interventions in immigrant women are not only a good investment with respect to achieving the stated target but may also help to control the situation in the countries of origin.
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We thank the collaboration in the making of this study of the Obstetrics and Clinical Pathology Departments of the following hospitals: Centre Mèdic Delfos, Consorci Hospitalari de Mataró, Centre Mèdic Sant Jordi de Sant Andreu, Fundació Sant Hospital de la Seu d’Urgell, H. Casa de la Maternitat de Barcelona, H. Clínic de Barcelona, H. Comarcal de Palamós, H. Comarcal de Mora d'Ebre, H. Comarcal de Sant Boi, H. Creu Roja de L’Hospitalet, H. Dr Trueta de Girona, H. General de Granollers, H. General Fundació Althaia de Manresa, H. General d'Igualada, H. Germans Trias i Pujol Badalona, H. Joan XXIII de Tarragona, H. Nª Sª del Remei de Barcelona, H. Materno-Infantil de la Vall d'Hebrón, H. Sagrat Cor de Barcelona, H. Sant Bernabé de Berga, H. Sant Jaume de Calella, H. Sant Jaume d'Olot, H. Sant Jaume de Blanes, H. Santa Creu i Sant Pau de Barcelona, H. Verge de Cinta de Tortosa, Pius Hospital de Valls, Quinta de Salut L'Aliança de Lleida. The study was funded by the Directorate of Public Health, Department of Health, Generalitat of Catalonia and by a grant from the Fondo de Investigaciones Sanitarias, Instituto de Salud Carlos III (RCESP, Epidemiology and Public Health Research Network).
Conflict of interest: None.
Key points
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