Evaluation of the measles, mumps and rubella immunisation programme in Spain by using a sero-epidemiological survey

Antibodies against measles and rubella virus among different age groups in Thailand: A population-based serological survey

Measles and rubella are highly contagious viral diseases transmitted via respiratory secretions and aerosolized droplets. Thailand has implemented universal vaccination against measles using the monovalent measles (M) or the trivalent measles-mumps-rubella (MMR) vaccine for the past 30 years. Nevertheless, incidence of measles and rubella remains in some parts of the country. We conducted a seroprevalence study to evaluate the antibodies to measles and rubella virus among Thais of all ages and to determine pre-existing immunity resulting from either vaccination and/or natural exposure. A total of 1,781 serum samples collected in 2014 was tested for IgG to measles and rubella virus by commercial enzyme-linked immunosorbent assays (ELISA). Percentages of individuals with protective antibody levels and the geometric mean concentrations (GMC) of IgG in each age group were analysed. The GMC of anti-measles IgG and anti-rubella IgG were 653.7 IU/L (95% confidence interval (CI); 555.9–751.4) and 39.5 IU/mL (95% CI;35.0–43.9), respectively. Thais between the ages of six months and 25 years did not demonstrate sufficient protective herd immunity for measles. This observation is consistent with the recent measles outbreaks in this age group. Lower prevalence of immunity against rubella was found among children ages 5–6 years who may not have completed vaccination as infants. Our findings identify gaps in rubella and measles immunity in specific age groups and support recommendations for catch-up MMR vaccination in individuals 30 years of age or younger.

Shift within age-groups of mumps incidence, hospitalizations and severe complications in a highly vaccinated population. Spain, 1998-2014

The mumps vaccine (Jeryl-Lynn-strain) was introduced in Spain in 1981, and a vaccination policy which included a second dose was added in 1995. From 1992-1999, a Rubini-strain based vaccine was administered in many regions but later withdrawn due to lack of effectiveness. Despite high levels of vaccination coverage, epidemics have continued to appear. We characterized the three epidemic waves of mumps between 1998 and 2014, identifying major changes in susceptible populations using Poisson regression. For the period 1998-2003 (P1), the most affected group was from 1 to 4years old (y) [Incidence Rate (IR)=71.7 cases/100,000 population]; in the periods 2004-2009 (P2) and 2010-2014 (P3) IR ratio (IRR) increased among 15-24y (P2=1.46; P3=2.68) and 25-34y (P2=2.17; P3=4.05). Hospitalization rate (HR), complication rate (CR) and neurological complication rate (NR) among hospitalized subjects decreased across the epidemics, except for 25-34y which increased: HR ratio (HRR) (P2=2.18; P3=2.16), CRR (P3=2.48), NRR (P3=2.41). In Spain mumps incidence increased, while an overall decrease of hospitalizations and severe complications occurred across the epidemics. Cohorts born during periods of low vaccination coverage and those vaccinated with Rubini-strain were the most affected populations, leading to a shift in mumps cases from children to adolescents and young adults; this also reveals the waning immunity provided by the mumps vaccine. Despite not preventing all mumps cases, the vaccine appears to prevent serious forms of the disease.

Seroprevalence of vaccine-preventable diseases among young children in the United Arab Emirates

OBJECTIVES

In the United Arab Emirates (UAE), many vaccine-preventable diseases are notifiable and are often reported despite high estimated immunization coverage. The serological assessment of immunity against these infections (serosurveillance) complements disease surveillance (notification). This study aimed to assess the yet unmeasured serological immunities to nine vaccine-preventable infections among vaccinated Emirati children.

METHODS

This cross-sectional study involved children who attended the Well-Child Care Programme of the Ambulatory Healthcare Services (Al-Ain, UAE) between July 2014 and September 2015. Serological testing was performed in 227 Emirati children (49% females); subjects were aged (mean±standard deviation) 45±14 months (median 43, range 23-71 months).

RESULTS

The seroprevalence rates varied markedly among the studied vaccine-preventable diseases, ranging from 39.2% (pertussis) to 98.3% (rubella). Other high seroprevalence rates were noted for measles (98.2%) and poliovirus (92%). The seroprevalence rate for mumps was 82.8%, for varicella was 68.3%, for diphtheria was 86.4%, for tetanus was 89.9%, and for Haemophilus influenzae type B was 84.1%.

CONCLUSIONS

A large number of the studied children had low seroprevalence rates against pertussis, varicella, and mumps. Studies are needed to explore whether modifying the national immunization programme could improve these low seroprevalence estimates.

Synthesis of Evidence to Characterize National Measles and Rubella Exposure and Immunization Histories

Population immunity depends on the dynamic levels of immunization coverage that countries achieve over time and any transmission of viruses that occur within the population that induce immunity. In the context of developing a dynamic transmission model for measles and rubella to support analyses of future immunization policy options, we assessed the model inputs required to reproduce past behavior and to provide some confidence about model performance at the national level. We reviewed the data available from the World Health Organization (WHO) and existing measles and rubella literature for evidence of historical reported routine and supplemental immunization activities and reported cases and outbreaks. We constructed model input profiles for 180 WHO member states and three other areas to support disease transmission model development and calibration. The profiles demonstrate the significant variability in immunization strategies used historically by regions and member states and the epidemiological implications of these historical choices. The profiles provide a historical perspective on measles and rubella immunization globally at the national level, and they may help immunization program managers identify existing immunity and/or knowledge gaps.

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.

A 16-year review of seroprevalence studies on measles and rubella

The determination of the seroprevalence of vaccine-preventable diseases is critical in monitoring the efficacy of vaccination programmes and to assess the gaps in population immunity but requires extensive organisation and is time and resource intensive. The results of the studies are frequently reported in peer-reviewed scientific, government and non-government publications. A review of scientific literature was undertaken to advise the development of WHO guidelines for the assessment of measles and rubella seroprevalence. A search of the National Library of Medicine's PubMed online publications using key words of 'measles', 'rubella', combined with 'serosurvey', 'seroprevalence', 'immunity' and 'population immunity' was conducted. A total of 97 articles published between January 1998 and June 2014 were retrieved, 68 describing serosurveys for measles and 58 serosurveys for rubella, conducted in 37 and 36 different countries respectively. Only 13 (19%) and 8 (14%) respectively were UN classified "least developed countries". The study sample varied markedly and included combinations of male and female infants, children, adolescents and adults. The study sizes also varied with 28% and 33% of measles and rubella studies respectively, having greater than 2000 participants. Microtitre plate enzyme immunoassays were used in 52 (76%) measles studies and 40 (69%) rubella studies. A total of 39 (57%) measles and 44 (76%) rubella studies reported quantitative test results. Seroprevalence ranged from 60.8% to 95.9% for measles and 53.0% to 99.3% for rubella studies. The review highlighted that infants lost maternally-acquired immunity within 9months of birth and were unprotected until vaccination. Two groups at higher risk of infection were identified: young adults between the ages of 15 and 30years and immigrants.

A review of testing used in seroprevalence studies on measles and rubella

Seroprevalence studies are an essential tool to monitor the efficacy of vaccination programmes, to understand population immunity and to identify populations at higher risk of infection. An overarching review of all aspects of seroprevalence studies for measles and rubella published between 1998 and June 2014 was undertaken and the findings reported elsewhere. This paper details the considerable variation in the testing formats identified in the review. Apart from serum/plasma samples, testing of oral fluid, breast milk, dry blood spots and capillary whole blood were reported. Numerous different commercial assays were employed, including microtitre plate assays, automated immunoassays and classical haemagglutination inhibition and neutralisation assays. A total of 29 of the 68 (43%) measles and 14 of the 58 (24%) rubella studies reported qualitative test results. Very little information on the testing environment, including quality assurance mechanisms used, was provided. Due to the large numbers of testing systems, the diversity of sample types used and the difficulties in accurate quantification of antibody levels, the results reported in individual studies were not necessarily comparable. Further efforts to standardise seroprevalence studies may overcome this deficiency.

High risk of a large measles outbreak despite 30 years of measles vaccination in The Netherlands

Our aim was to assess progress towards measles elimination from The Netherlands by studying humoral measles immunity in the Dutch population. A population-based seroepidemiological study was conducted in 2006-2007 (N = 7900). Serum samples were analysed by a bead-based multiplex immunoassay. IgG levels ⩾0·2 IU/ml were considered protective. The overall seroprevalence in the Dutch population was 96%. However, 51% of socio-geographically clustered orthodox Protestant individuals aged <10 years were susceptible. Infants might be susceptible to measles between ages 4 months and 14 months, the age at which maternal antibodies have disappeared and the first measles, mumps, rubella (MMR) vaccination is administered, respectively. Waning of antibody concentrations was slower after the second MMR vaccination than after the first. The Netherlands is at an imminent risk of a measles outbreak in the orthodox Protestant minority. To prevent subsequent transmission to the general population, efforts to protect susceptible age groups are needed.

Seroprevalence of antibodies against measles, rubella, mumps, varicella-zoster, and B. Pertussis in young adults of Madrid, Spain

In recent years, there has been an increase in the number of cases of certain immunopreventable diseases in our country. A high proportion of these have been recorded among the young adult population. The aim of this study was to determine the seroprevalence of antibodies against immunopreventable diseases with the greatest health impacts on the young adult population (19-39 y of age) in Madrid. We collected a total of 1,153 serum samples from healthy volunteers undergoing routine medical visits and used ELISA to determine the presence of IgG antibodies against measles, rubella, mumps, and varicella zoster, as well as Bordetella pertussis. The Pearson's χ(2) test was used to compare prevalences, the Mann-Whitney U test was used to compare means, and the Kruskal-Wallis test was applied for variables with more than 2 categories. Statistical significance was achieved with p values of<0.05. The global prevalence of antibodies was 92.1% for measles, 94.4% for rubella, 88.3% for mumps, 92.8% for varicella zoster, and 70.2% for B. pertussis. No statistically significant differences were found between genders. The prevalence of antibodies against measles was more than 95% in the group of individuals born after 1986, and the percentage of individuals susceptible to rubella was less than 5% in women born after 1986. In spite of adequate vaccination coverage, in our region, a population of young adults exists who have not achieved the objectives of the WHO for the elimination of measles and congenital rubella syndrome.

Prevalence of measles, mumps, rubella, and varicella susceptibility among health science students in a University in India

BACKGROUND

Health science students (HSS) are at increased risk of contracting and transmitting viral diseases such as measles, mumps, rubella, and varicella (chickenpox). This study was undertaken to determine the prevalence of susceptibility of HSS to these infections.

METHODS

Using a cross-sectional design, 790 HSS of Manipal University, Manipal, India, answered a questionnaire and provided a blood sample which was tested for specific IgG antibodies to measles, mumps, rubella and varicella by ELISA (Enzygnost(®)).

RESULTS

The study group was comprised of medical (53.9%), nursing (16.6%), and allied health (29.5%) students. Among the overall group (n = 790), the prevalence of serological susceptibility to measles, mumps, rubella, and varicella were 9.5%, 32.0%, 16.6%, and 25.8%, respectively. Among the subgroup of vaccinated subjects, susceptibility to measles, mumps, rubella, and varicella were 7.9%, 34.7%, 10.7%, and 35.2%, respectively.

CONCLUSION

HSS susceptible to measles, mumps, rubella, and/or varicella are at risk of acquiring these diseases during their training period. In addition, they may be a potential source for nosocomial transmission posing a risk to immunocompromised patients. Hence, in the Indian setting, HSS should be immunized against measles, mumps, rubella, and varicella at the time of joining the medical school.

Hospitalizations due to rotavirus gastroenteritis in Catalonia, Spain, 2003-2008

Background

Rotavirus is the most common cause of severe gastroenteritis among young children in Spain and worldwide. We evaluated hospitalizations due to community and hospital-acquired rotavirus gastroenteritis (RVGE) and estimated related costs in children under 5 years old in Catalonia, Spain.

Results

We analyzed hospital discharge data from the Catalan Health Services regarding hospital admissions coded as infectious gastroenteritis in children under 5 for the period 2003-2008. In order to estimate admission incidence, we used population estimates for each study year published by the Statistic Institut of Catalonia (Idescat). The costs associated with hospital admissions due to rotavirus diarrhea were estimated for the same years. A decision tree model was used to estimate the threshold cost of rotavirus vaccine to achieve cost savings from the healthcare system perspective in Catalonia. From 2003 through 2008, 10655 children under 5 years old were admitted with infectious gastroenteritis (IGE). Twenty-two percent of these admissions were coded as RVGE, yielding an estimated average annual incidence of 104 RVGE hospitalizations per 100000 children in Catalonia. Eighty seven percent of admissions for RVGE occurred during December through March. The mean hospital stay was 3.7 days, 0.6 days longer than for other IGE. An additional 892 cases of presumed nosocomial RVGE were detected, yielding an incidence of 2.5 cases per 1000 child admissions. Total rotavirus hospitalization costs due to community acquired RVGE for the years 2003 and 2008 were 431,593 and 809,224 €, respectively. According to the estimated incidence and hospitalization costs, immunization would result in health system cost savings if the cost of the vaccine was 1.93 € or less. At a vaccine cost of 187 € the incremental cost per hospitalization prevented is 195,388 € (CI 95% 159,300; 238,400).

Conclusions

The burden of hospitalizations attributable to rotavirus appeared to be lower in Catalonia than in other regions of Spain and Europe. The relatively low incidence of hospitalization due to rotavirus makes rotavirus vaccination less cost-effective in Catalonia than in other areas with higher rotavirus disease burden.

Are we hitting immunity targets? The 2006 age-specific seroprevalence of measles, mumps, rubella, diphtheria and tetanus in Belgium

Susceptibility to vaccine-preventable diseases in Belgium in 2006 was estimated from a serum survey. Immunoglobulins against measles, mumps, rubella (MMR) and diphtheria at all available ages (1-65 years), and against tetanus in >40-year-olds, were measured by ELISA. Age-standardized overall seronegativity for MMR was low (3·9%, 8·0%, 10·4%, respectively). However, the World Health Organization's targets for measles elimination were not met in 5- to 24-year-olds and about 1 in 7 women at childbearing age (15-39 years) were seronegative for rubella. In adults >40 years, tetanus immunity (87·2%, >0·16 IU/ml) largely exceeded diphtheria immunity (20-45%, >0·1 IU/ml). Despite free universal vaccination against MMR for more than 20 years and against diphtheria and tetanus for almost 60 years, our study revealed specific age groups remaining at risk for infection with these pathogens.

Measles risk groups in Spain: implications for the European measles-elimination target

The European Region has set itself the goal of eliminating measles by 2010. Incidence has increased in recent years. This study sought to investigate outbreaks in Spain in the period 2005-2007, in order to identify measles-vulnerable groups and compare Spain to other European countries which have also had measles outbreaks. The pattern observed for Spain proved different to that of other European countries, i.e., whereas young adults and infants aged under 15 months were affected in Spain, children aged under 9 years comprised the predominant group in other European countries. Measles cases in Spain reflect low coverage when vaccination began, a pattern that could be repeated in neighbouring countries. Vaccination efforts should thus be targeted at vulnerable groups, namely: young adults; health professionals; travelling communities; and adopted infants and foreigners from countries with important pockets of susceptibles.

Internationally adopted children: what vaccines should they receive?

It is of paramount importance to know the vaccination status in internationally adopted children, so that they can be correctly immunized. This study ascertains the seroprotection rate for vaccine-preventable diseases and the validity of the immunization cards in 637 adopted children. The absence of the immunization card (13% of children) correlated with a poor global vaccine protection. Children with immunization records (87%) had a better global seroprotection but the information obtained from the card did not accurately predict seroprotection for each particular antigen. The best variable to predict the status of seroprotection was the country of origin. The highest rate of protection was found in children from Eastern Europe and, in descending order, India, Latin America, China and Africa. General recommendations for immunization of internationally adopted children are difficult to establish. Actions for vaccination have to be mainly implemented on the basis of the existence of the immunization card and of the country of origin.

Detection of measles- and mumps-specific IgG antibodies in paired serum and oral fluid samples from Norwegian conscripts

The aim of this study was to measure the seroprevalence to mumps in Norwegian conscripts belonging to the first children vaccination cohorts that had been offered two doses of MMR vaccine. The seroprevalence to mumps was 76% with the Microimmune assay and 85% with the Enzygnost assay. We also compared the performance of the Microimmune assay for detection of mumps- and measles-specific IgG antibodies in 340 paired serum and oral fluid samples from the conscripts and evaluated the effect of revaccination. Mumps-specific IgG antibodies were detected in only 61% of the oral fluids. In contrast, high levels of measles-specific IgG antibodies were detected in both the serum and oral fluid samples. Based on these results, we are only able to recommend the use of oral fluid for surveillance of measles in Norway. Our results may also indicate that the seroprevalence necessary to interrupt transmission of mumps has not been reached in vaccinated young adult Norwegians. Seroconversion was observed in all initially measles seronegative conscripts after revaccination, whereas 23 of 27 initially mumps seronegative conscripts failed to seroconvert.

Prevalence of mumps antibodies in the Israeli population in relation to mumps vaccination policy and incidence of disease

We examined the prevalence of mumps antibodies in the Israeli population in relation to mumps vaccination policy and past and subsequent incidence of disease. The levels of specific IgG antibodies against mumps were tested in 3330 residual sera collected during 1997-1998 from an age-stratified population sample. Against the background of a consistent MMR vaccination coverage of >90%, the age- and sex-adjusted seropositivity to mumps was 77.0%. No significant differences between genders were found. Seropositivity in the 10-13 years age group, born just before the introduction of the MMR vaccine, was the lowest (59%). These birth cohorts were the target of an outbreak of mumps in 2005 that occurred among high-school students and military recruits. A trend of waning immunity was observed between the first and second vaccine doses. The seroepidemiological data demonstrate that immunity levels below the herd immunity threshold, along with social mixing and crowded conditions facilitated the occurrence of mumps outbreaks. Periodical serosurveys are an essential component in the evaluation of the vaccination policy against mumps.

Rubella seroprofile of the Italian population: an 8-year comparison

The objective of this study is to evaluate how increasing MMR infant vaccination coverage in recent years has modified the epidemiology of rubella in Italy. A cross-sectional population-based seroprevalence study of rubella antibodies was conducted on 3094 sera, in 2004, and results were compared with data obtained by the same method in 1996. The overall proportion of rubella-seropositive individuals was found to be significantly higher in 2004 with respect to 1996 (84.6% vs. 77.4%). However, an increase in seropositivity was observed only in the 1-19 years age groups. Recent increases in childhood MMR vaccination coverage, therefore, have not had an impact on seroprevalence in women of childbearing age, over 5% of whom remain susceptible to rubella. Preconception screening and postpartum vaccination of susceptible women are fundamental if the WHO target of less than one case of congenital rubella syndrome per 100,000 live births is to be attained.

Sensitivity and specificity of immunoglobulin G titer for the diagnosis of mumps virus in infected patients depending on vaccination status

The aim of the study was to evaluate the usefulness of serological detection of mumps IgM and titration of IgG in patients with acute parotitis according to their vaccination status. The detection of mumps virus RNA in saliva by RT-PCR was used as reference. 116 patients (109 of them previously vaccinated) with mumps RT-PCR-negative results and 21 (19 vaccinated) with mumps RT-PCR-positive results were studied. Mumps-specific IgM and IgG were assayed by EIA (Enzygnost, Dade Behring, Germany). IgM results were expressed as positive or negative. For IgG, several cut-offs were calculated using receiver operating characteristic (ROC) curves. Seven RT-PCR-positive and five RT-PCR-negative patients showed IgM-positive results (sensitivity 33.3% and specificity 95.7%). Among vaccinated patients, the sensitivity and specificity of IgM were 26.3% (5/19) and 99.1% (108/109). For IgG, a titer of 5,000 in all the patients showed a sensitivity of 76.2% (16/21) and a specificity of 83.6% (97/116). In vaccinated patients, the corresponding figures for this cut-off were 84.2% (16/19) and 83.5% (91/109), respectively. Although IgM detection against mumps is highly specific, its sensitivity is very low in immunized subjects. In this group, the titration of IgG could serve as an additional diagnostic tool.

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.

Seroepidemiology study of rubella antibodies among pregnant women from seven Asian countries: Evaluation of the rubella vaccination program in Taiwan

During 2003-2004, approximately 13% of birth in Taiwan was given by foreign-born females. The aims of this study were to compare the seroprevalence of rubella antibodies between Taiwan-born and foreign-born pregnant women and evaluate the effect of rubella vaccination program in Taiwan. We reviewed the rubella antibody test results of 5007 women during routine pregnancy check-ups at Fooyin University Hospital during 1999-2002. In Taiwan-born women, rubella antibody was undetectable in 29.2%, 7.3%, and 8.3% of the cohorts born before 1971, between 1971 and 1976, and after 1976, respectively. In the cohorts born between 1971 and 1976 and after 1976, pregnant women born in China, Vietnam, Indonesia, and Philippines had significant higher chances of being susceptible. Our results suggested that the voluntary adult vaccination program was not as effective as the school or wipe-out programs. Both Taiwanese women born before 1971 and foreign-born women were more likely to be susceptible to rubella. The introduction of 'catch-up' immunization program and enforcement of the checking of immunization record and/or blood test before pregnancy for these women are necessary in preventing CRS.

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.

Evaluation of diagnostic markers for measles virus infection in the context of an outbreak in Spain

A measles outbreak occurred from January to July 2003 in Spain, despite the fact that the Plan of Eradication of Measles and its surveillance program had been set up in 2001. Different diagnostic markers for measles virus infection were compared for 246 patients in tests of serum, urine, and pharyngeal exudate specimens. Measles virus immunoglobulin M (IgM) and IgG and rubella virus and parvovirus IgM levels in serum were assayed. Multiplex PCR was done on urine, serum, and pharyngeal exudates, and isolation of measles virus in the B 95 a cell line from urine was attempted. At least one positive marker for measles virus was obtained from 165 patients (67.1%; total number of patients, 246). A total of 136 cases (82.4% of the patients showing positive markers) were diagnosed by PCR and/or isolation and IgM detection methods. The results for 27 patients (16.4%) were positive only by direct methods. The results for two patients (1.2%) were positive only by IgM detection. In the case of the first group (136 cases), the time elapsed from appearance of the rash was significantly longer than in the case of the group which was only positive by PCR. Besides, 8 out of 27 PCR-positive IgM-negative cases showed specific IgG results, suggesting either secondary vaccine failure or reinfection. Numbers resulting from PCR performed with pharyngeal exudates proved to be significantly higher than those obtained with other specimens. Phylogenetic analysis showed the presence of genotype B3. The results strongly back the World Health Organization recommendation that detection of IgM should be supplemented by PCR and isolation for the diagnosis of measles virus infection.

Detection of secondary mumps vaccine failure by means of avidity testing for specific immunoglobulin G

The aim of this study was to discriminate between primary and secondary vaccine failure in children with mumps using IgG avidity testing. Thirty-nine serum samples from children with mumps, confirmed by specific IgM, were studied. The patients were grouped according to their immunization status. The secondary immune response was defined by IgG with an avidity index >32%. A secondary response in infected children previously immunized was considered as a secondary vaccine failure. Vaccinated children presented higher IgG titers and IgG avidity than unvaccinated children. The proportion of secondary immune responses in unvaccinated patients was lower than that obtained in previously vaccinated infected patients. Avidity testing can be a useful tool to detect secondary vaccine failure in mumps.

Sero-epidemiology of measles and mumps in Korea: impact of the catch-up campaign on measles immunity

A catch-up campaign targeting children aged 8-16 years using measles-rubella (MR) vaccine was conducted during 2001 in Korea. To evaluate the impact of the campaign and assess mumps immunity, human IgG antibodies were detected using ELISA for measles (5826 samples) and mumps (5890 samples) in a national sample of opportunistically collected sera from a population aged 0-34 years. The measles immunity increased by 5-10% following the catch-up campaign in the targeted age group. Infants lost maternal antibodies rapidly and about 90% of infants were susceptible to measles and mumps at 6-8 months of life. The sero-prevalence of mumps antibody increased slowly with age and stabilized at a lower level when compared with that of measles. Despite an immediate reduction in susceptibility among the targeted age group of the catch-up campaign, continuous efforts to increase immunization coverage are needed to interrupt indigenous measles transmission. Furthermore, our results suggest continuous mumps outbreaks could occur because of the accumulation of susceptible individuals.