Serological evidence of reinfection among vaccinees during rubella outbreak

Use of rubella seroepidemiological data for assessment of previous vaccination policy and for decision making in response to epidemics in Israel

We examined the prevalence of rubella antibodies in a representative sample of the Israeli population. Three thousand three hundred and twenty-six sera collected during 1997 and 1998, from an age-stratified general population sample were tested for specific IgG antibodies against rubella. The sero-positivity rates to rubella were higher among females as compared with males (89.1% versus 82.3%, respectively (p < 0.001). This difference was the result of much lower sero-positivity rates among males in the age group 13-17, with the lowest value (56.3%) among subjects aged 16. Male subjects of this age group were in 2000 the target of an outbreak of rubella among 18-19-year old male recruits of the Israel Defense Force. The data of this study served to assess previous exposure to the wild virus or vaccine strains, to identify pockets of low level of immunity and contributed to decision making in response to the onset of a rubella outbreak.

Cytokine profile after rubella vaccine inoculation: evidence of the immunosuppressive effect of vaccination

BACKGROUND AND AIM: Immunization with live virus vaccines may cause an immunosuppression with lymphopaenia, impaired cytokine production and defective lymphocyte response to mitogenes. These abnormalities were described in subjects vaccinated against measles. This study was performed to analyse the host immune response related to immunosuppression in subjects vaccinated with live attenuated rubella vaccine. METHODS: Eighteen schoolgirls, aged 11-13 years, were vaccinated with live attenuated rubella vaccine Rudivax. Before immunization, and 7 and 30 days after, peripheral blood was collected. Cellular fractions were subjected to flow cytometric analysis, and the lymphocyte response to phytohaemagglutinin was investigated. Plasma samples were analysed for cytokines (interleukin (IL)-4, IL-10, tumour necrosis factor-alpha, and interferon-gamma) by enzyme-linked immunosorbent assay techniques. RESULTS: On day 7 after vaccination, the number of each lymphocyte subset was decreased; however, only for CD3 and CD4 lymphocytes has a significant reduction been shown. On the contrary, tumour necrosis factor-alpha and IL-10 levels markedly increased and amounted to its maximum on day 30. Simultaneously, a significant reduction in plasma interferon-gamma and a profound decrease of the lymphocyte response to phytohaemagglutinin were shown. The changes were accompanied with marked elevation of plasma IL-4. CONCLUSIONS: Our data indicate that the vaccination with live attenuated rubella vaccine results in moderate but sustained immune disturbance. The signs of immunosuppression, including defective lymphocyte response to mitogene and impaired cytokine production, may persist for at least 1 month after vaccination.

A synthetic peptide ELISA for the screening of rubella virus neutralizing antibodies in order to ascertain immunity

One hundred and fifty-one human sera from patients exposed to rubella virus (RV) and shown to be negative for IgM antibodies were tested for total RV-IgG, hemagglutination inhibition (HAI) and for virus neutralizing (VN) antibodies using a peptide enzyme-linked immunosorbent assay (ELISA) based on BCH-178, a peptide representing one of several known neutralizing epitopes on RV hemagglutinin (E1). The data showed that, among 39 and 51 sera with HAI and RV-IgG titres of 1/128 and >150 IU/ml, respectively, neutralizing antibody readings using the BCH-178 ELISA were above cut-off values. However, 13% of HAI positive sera (titre > or =1/16) and 16% of RV-IgG ELISA positive sera (> or =20 IU/ml) were below the cut-off value of the BCH-178 ELISA. This may explain why several cases of congenital rubella syndrome (CRS) have been observed in spite of positive titres. We suggest that a diagnosis of sufficient immunity against RV infection or reinfection may be safer if an additional test detecting antibodies against VN RV epitopes is positive as well.

Evaluation of antibodies against a rubella virus neutralizing domain for determination of immune status

The protective immune responses against rubella virus (RV) are related to its neutralizing epitopes, an issue that is important to consider when assessing the immune status of patients with remote infection. In the present paper, we compare the antibodies detected by a synthetic-peptide-based enzyme immunoassay (EIA) with antibodies detected by the traditional technique of hemagglutination inhibition (HIA) in patients with remote RV infection. The synthetic peptide used as an antigen (SP15) represents a neutralizing epitope that corresponds to amino acids 208 to 239 of the E1 glycoprotein. The SP15-EIA was developed, all variables that affected the assay were standardized, and the test was validated using reference sera. Serum samples (n = 129) from patients with remote RV infection were tested by HIA and SP15-EIA. Discrepant sera were assayed by MEIA (IMX/Abbot). The comparison between HIA and SP15-EIA, taking HIA as the standard methodology for determining immune status, showed that SP15-EIA is very specific and sensitive for detecting protecting antibodies (specificity, 100%; sensitivity, 98.20%). This study demonstrates that antibodies against the neutralizing domain represented by SP15 would be important in the memory response after natural infection and may be a good tool in the determination of the true immune status of patients with remote infection with regard to RV.

Clinical rubella reinfection during pregnancy in a previously vaccinated woman

We report a documented case of clinically apparent rubella reinfection during pregnancy with rubelliform rash and fever followed by lymphodenopathy at the 18th week of gestation, in a previously vaccinated woman with haemagglutination inhibition (HI) antibody titre of 1:32. The serological tests results (including neutralizing antibodies) demonstrated a significant rise in her rubella specific IgG level with strongly positive IgM reactivity. In addition, rubella-specific IgG antibody avidity testing displayed high avidity index (53-88%) typical of rubella reinfection. Umbilical cord blood, drawn by sonographic-guided cordocentesis at 24 weeks' gestation, was found to be negative for rubella-specific IgM antibody. The pregnancy was continued to term, and a healthy infant was born.

Duration of rubella immunity induced by two-dose measles, mumps and rubella (MMR) vaccination. A 15-year follow-up in Finland

A national two-dose vaccination program with a combined measles, mumps and rubella (MMR-II) vaccine was introduced in Finland, in 1982, immunizing children at the ages of 14-18 months and 6 years. Antibody levels were determined from serial samples from a group of originally 350 children during 15 years. The latest samples were taken 15.5 years after the first vaccination and 70% of the children could still be reached. The aim of this study was to determine the kinetics of rubella antibodies induced by the MMR-II vaccine in these individuals. Rubella antibodies were analyzed from three different cohorts: Group I seronegative children (n=166) vaccinated at 14-18 months and 6 years, Group II seronegative children (n=139) and Group III seropositive children (n=16) vaccinated at 6 and 11-13 years. Samples collected 0-9 years after vaccination were analyzed by hemolysis-in-gel (HIG) and later samples by enzyme immunoassay (EIA) techniques. The primary vaccination induced 100% seropositivity in vaccinees with a mean zone diameter of 10 (+/-1.3), 10.2 (+/-1.1) and 11.5 (+/-0.9) mm, in Groups I, II and III, respectively. The seropositivity rate was still high at 15 years, 99%, 100% and 100% with the geometric mean titer 23, 46 and 105 IU/ml, respectively. At 15 years, antibody levels <15 IU/ml which is the suggested protective level, were found in 31, 9 and 0% of children in Groups I, II and III, respectively. Because almost a third of the individuals in Group I now, at the age of 17 years, had low levels of rubella antibodies, it is possible that rubella infections may re-emerge during pregnancy. A careful surveillance including serological follow-up is therefore very important.

Subclinical rubella reinfection during pregnancy followed by transmission of virus to the fetus

We report a documented case of rubella reinfection during pregnancy in a previously vaccinated woman with residual antibody titre to rubella of 15 IU/ml. The reinfection occurred following an exposure to rubella virus (contact with 6-year-old daughter with clinical rubella) between the 7th and 10th week of pregnancy which resulted in transmission of the virus to the fetus. Umbilical cord blood drawn by cordocentesis was found to be strongly positive for rubella IgM antibody. After termination of the pregnancy rubella virus was isolated in cell culture from fetal tissues.

The incidence of rubella virus infections in Switzerland after the introduction of the MMR mass vaccination programme

We have collected data on the incidence of rubella in Switzerland from 1987 to 1992 to help evaluating the impact of the measles, mumps and rubella (MMR) mass vaccination programme which started in 1985 in this country. We used detailed informations on samples submitted for diagnostic testing in conjunction with anonymous laboratory notifications to the Swiss Federal Office for Public Health, and data from the Swiss sentinel network of general practitioners to find trends in the incidence of rubella after the introduction of mass vaccination. We observed an unabated seasonal oscillation without decreasing trend during the observation period and were unable to detect a shift in the age distribution of cases. An important proportion of laboratory-confirmed rubella occurred in women of childbearing age. Immigrants from regions with low endemicity of rubella were at increased risk of contracting rubella and transmitting it to their offspring. We conclude, that MMR mass vaccination has not interrupted the circulation of rubella virus in Switzerland, and that improvements in the implementation and surveillance of the MMR vaccination campaign are necessary in order to avoid untoward effects of it.

Duration of the immune response to MMR vaccine in children of two age-different groups

A combined vaccine against measles, mumps and rubella (MMR) was administered to both a group of children aged 10-12 months simultaneously with booster doses of compulsory diphtheria-tetanus toxoids and oral poliovirus vaccine and a group of children aged 15-24 months who had previously received booster doses of the compulsory vaccines. Apart from one subject belonging to the second group who was non responder and one from the same group who did not seroconvert against the mumps virus alone, 5 to 6 weeks after MMR vaccine administration we found protective levels of antibodies against measles, mumps and rubella viruses in all children. The follow up of both groups at 3 years did not reveal difference between the two groups. Protective levels of serum antibodies against measles and mumps were found in the two groups, although a significant decline of rubella antibodies was shown (p < 0.05). Since the immunogenicity of the vaccines in the two groups did not differ, we recommend that the scientific community reconsider the vaccination schedule until now recommended. In our opinion the MMR vaccine should be administered simultaneously with booster doses of diphtheria-tetanus toxoids and oral poliovirus vaccine at 10-12 months of age because this policy improves parents' compliance, markedly reduces community costs and simplifies routine immunization schedule.

Congenital rubella syndrome after maternal reinfection

This report concerns a case of congenital rubella syndrome (CRS) with atypical immune response affecting an infant whose mother had repeated evidence of immunity before pregnancy. Laboratory diagnosis of CRS could only clearly be achieved by virus isolation after the second month of life despite typical clinical features of CRS and multiple organ involvement. After the first month of age, low concentrations of specific IgM antibodies were revealed by ELISA and confirmed by a reference test system (IgM-specific haemagglutination inhibition assay). Persistent and increasing high levels of IgM antibodies were detected only after the 6th month of life. Later on IgG antibody levels decreased. Immunological investigations showed an IgG1-hypoglobulinaemia. The unusual feature of the present case report is not only the failure of the maternal rubella immunity to prevent CRS, but the defect of the child's immune system, probably attributable to congenital infection. As a consequence, laboratory diagnosis of CRS could not be achieved initially by the proved serological methods.

Possibility of reinfection after immunisation with RA27/3 live attenuated rubella virus

A serological study was carried out on 527 girls immunized with RA 27/3 rubella vaccine. Data from all scheduled serum samples over a 5-year follow-up were available for 102 vaccinees, 10 (9.8%) of whom showed evidence of reinfection during the 5th year after immunisation, a year in which there was a rubella outbreak in the Siena area (Italy). We examined in greater detail the serological responses of these vaccinees after reinfection and the consequent implications pertinent to the duration of the protective immunity.