Current lessons from 20th century serosurveillance data on rubella

Lack of immunity against rubella among Italian young adults

BACKGROUND

To support the evaluation of the 2010-15 National Plan for Measles and Congenital Rubella Elimination, the authors designed and performed a serosurveillance survey to verify the immunity/susceptibility rate against rubella among Apulian young adults.

METHODS

The study was carried out from May 2011 to June 2012 in the Department of Transfusion Medicine/Blood Bank of Policlinico General Hospital in Bari. Subjects were enrolled by a convenience sampling. For each enrolled patient a 5 ml serum sample was collected and tested for anti-rubella IgG. The geometrical means (GMT) of anti-rubella IgG was calculated. T student test or ANOVA test, when appropriate, was used to compare the means of age per gender and GMT of anti-rubella IgG titres per age classes. Chi-square test was used to compare the proportion of anti-rubella IgG positive subjects per gender and per age classes. For all tests, a p value <0.05 was considered as significant.

RESULTS

At the end of the study 1764 subjects were enrolled, 1362 (77.2%) of which were male. The mean age was 38.4 ± 11.7 years (range: 17-65). 86.7% (95% CI = 85.0-88.2) had a positive titre of anti-rubella IgG. GMT of anti-rubella IgG titre was 4.3. The proportion of positive subjects was of 76.8% (n = 279/363; 95% CI = 72.2-81.1) in persons aged 18-26 years; 88.1% (n = 310/352; 95% CI = 84.2-91.3) in 27-35 year-old people; 88.5% (n = 464/524; 95% CI = 85.5-91.1) in 36-45 year-old people; 90.7% (n = 350/386; 95% CI = 87.3-93.4) among people aged 46-55 years and 90.6% (n = 126/139; 95% CI = 84.5-94.9) in 55-65 year-old people (Chi-square = 39.7; p < 0.0001). GMT of anti-rubella IgG titre was 4.3 (4.3 in male and 4.2 in female, t = 2.2; p = 0.03) and seems to differ dividing the enrolled subjects by age group (F = 14.3; p < 0.0001).

CONCLUSIONS

According to our data, too many women of child-bearing age are still unprotected from rubella in the elimination era and in this scenario the public health efforts should be oriented to catch-up activities.

Seroprevalence of measles, rubella, and mumps antibodies in Catalonia, Spain: results of a cross-sectional study

Determination of antibody levels against vaccine-preventable diseases is of great value to assess immunization programmes. The objective of this study was to determine the prevalence of measles, rubella, and mumps antibodies in representative samples of the child and adult population of Catalonia and compare the findings to those obtained in 1996. A representative sample of the child and adult (>or=15 years) population of Catalonia was studied. Enzyme-linked immunosorbent assay techniques were used to determine the presence of antibodies. Equivocal results for antibodies against measles and rubella were tested using an immunofluorescence technique. To compare proportions, the chi-square test and the Fisher's exact test were used. Statistical significance was set at 0.05. Adjusted odds ratios were calculated using multiple logistic regression analysis. Samples from 2,619 people were analyzed. The global prevalence of antibodies was 98.3% for measles, 91.1% for mumps, and 98.1% for rubella. The prevalence of rubella antibodies was higher in women than in men (98.8 vs. 97.2%, respectively). Compared with the results obtained in the 1996 seroprevalence study, only the prevalence of rubella antibodies showed a statistically significant increase in men (97.2 vs. 94.6%; p=0.002) and, in particular, in women (98.8 vs. 95.3%; p<0.001). The low prevalence of susceptible subjects has already led to the elimination of indigenous measles in Catalonia and should allow the elimination of indigenous rubella by 2005. The level of antibodies necessary to interrupt the transmission of mumps has still not been reached in all age groups.

Estudio del rendimiento diagnóstico de la detección de IgM específica y de la amplificación genómica de rubéola

Nowadays, most exanthematic diseases for which a vaccine is available affect young adults. A large percentage of these cases prove to be rubella. The aim of this study is to assess the performance of specific IgM and RT-PCR for the diagnosis of rubella infection. Fifty-nine patients with clinically suspected measles or rubella, and with available serum, whole blood, urine and pharyngeal exudate specimens were studied. RT-PCR in pharyngeal exudate was found to be the most effective marker at the start of the disease (mean, 2.5 days). IgM detection yielded a larger percentage of positive results (76.2%), but at a later time (3.7 days).

Rubéola: el nuevo escenario de una vieja enfermedad

World Health Organization has the target by the year 2010 of reducing congenital rubella syndrome to less than 1/100,000 live births, being necessary the control of the virus circulation. Rubella is currently a low-incidence disease, that affected to children in the pre-vaccine era. The excellent measles-mumps-rubella vaccine coverage in children, together with the vaccination campaigns in childbearing age women, leads to get very high protection. Until recently, susceptible individuals were grouped in a reduced fraction of young men, born after the decline of wild virus circulation and that did not receive the vaccine, due to its age. The new demographic situation derived from the immigration is causing important changes in the susceptibility pattern. Many immigrants came to Spain from regions where rubella vaccine is not (or until recently was not) administered; as result, it can emerge an accumulation of susceptible individuals (especially among adults) allowing the re-circulation of the virus.