Surveillance of antibody to measles, mumps, and rubella by age

Targeted sampling reduces the uncertainty in force of infection estimates from serological surveillance

Age bins are frequently used in serological studies of infectious diseases in wildlife to deal with uncertainty in the age of sampled animals. This study analyzed how age binning and targeted sampling in serological surveillance affect the width of the 95% confidence interval (CI) of the estimated force of infection (FOI) of infectious diseases. We indicate that the optimal target population with the narrowest 95% CI differs depending on the expected FOI using computer simulations and mathematical models. In addition, our findings show that we can substantially reduce the number of animals required to infer transmission risk by tailoring targeted, age-based sampling to specific epidemiological situations.

Rubella infection in pregnancy and congenital rubella in United Kingdom, 2003 to 2016

Rubella vaccination has been included in the United Kingdom's (UK) routine childhood schedule for nearly 30 years. The UK achieved World Health Organization (WHO) elimination status in 2016 and acute rubella infections are rare. In the period 2003-16, 31 rubella infections in pregnancy (0.23 per 100,000 pregnancies) were identified through routine surveillance, of which 26 were in women who were born abroad. Five of the 31 rubella infections led to congenital rubella syndrome in the infant and three had confirmed congenital rubella infection without congenital rubella syndrome. An additional seven babies were identified with congenital rubella syndrome, although rubella infection in pregnancy had not been reported. Place of birth was known for six of these seven mothers, all of whom were born outside the UK, and in five cases maternal infection was acquired abroad. WHO Europe has set targets for measles and rubella elimination and prevention of congenital rubella syndrome by 2015. Vaccination uptake and rubella immunity is high in the UK population and most infections in pregnancy since 2003 were acquired abroad and in unvaccinated women. Every contact with a health professional should be used to check that women are fully immunised according to UK schedule.

Evidence of Mumps Infection Among Children in the Democratic Republic of Congo

BACKGROUND

Mumps is an acute viral infection and while the infection is usually mild, complications can lead to permanent sequelae including brain damage and deafness. The burden of mumps is currently unknown the Democratic Republic of Congo (DRC), we therefore assessed susceptibility to mumps infection among children 6-59 months of age.

METHODS

In collaboration with the 2013-2014 DRC Demographic and Health Survey, we conducted a serosurvey to assess population immunity to vaccine preventable diseases. Dried blood spot samples were collected from children 6 to 59 months of age and processed at the UCLA-DRC laboratory in Kinshasa, DRC using the Dynex Technologies Multiplier FLEX chemiluminescent immunoassay platform (Dynex multiplex assay, Chantilly, VA). Logistic multivariate analyses were used to determine risk factors for mumps seropositivity.

RESULTS

Serologic and survey data were matched for 7195, 6-59 month-old children, among whom 22% were positive and 3% indeterminate for mumps antibodies in weighted analyses. In multivariate analyses, the odds of seropositivity increased with increasing age, female gender, number of children in household, increasing socioeconomic status and province (Kinshasa with the highest odds of positive test result compared with all other provinces).

CONCLUSION

These data suggest that mumps virus is circulating in DRC and risk of exposure increases with age. At present, the introduction of a combined measles-mumps-rubella vaccine remains unlikely, as the capacity to maintain adequate vaccine coverage levels for routine immunization must be improved before additional antigens can be considered for the routine immunization schedule.

Waning Immunity Is Associated with Periodic Large Outbreaks of Mumps: A Mathematical Modeling Study of Scottish Data

Vaccination programs for childhood diseases, such as measles, mumps and rubella have greatly contributed to decreasing the incidence and impact of those diseases. Nonetheless, despite long vaccination programmes across the world, mumps has not yet been eradicated in those countries: indeed, large outbreaks continue. For example, in Scotland large outbreaks occurred in 2004, 2005, and 2015, despite introducing the MMR (Measles-Mumps-Rubella) vaccine more than 20 years ago. There are indications that this vaccine-preventable disease is re-emerging in highly vaccinated populations. Here we investigate whether the resurgence of mumps is due to waning immunity, and further, could a booster dose be the solution to eradicate mumps or would it just extend the period of waning immunity? Using mathematical modeling we enhance a seasonally-structured disease model with four scenarios: no vaccination, vaccinated individuals protected for life, vaccinated individuals at risk of waning immunity, and introduction of measures to increase immunity (a third dose, or a better vaccine). The model is parameterised from observed clinical data in Scotland 2004–2015 and the literature. The results of the four scenarios are compared with observed clinical data 2004–2016. While the force of infection is relatively sensitive to the duration of immunity and the number of boosters undertaken, we conclude that periodic large outbreaks of mumps will be sustained for all except the second scenario. This suggests that the current protocol of two vaccinations is optimal in the sense that while there are periodic large outbreaks, the severity of cases in vaccinated individuals is less than in unvaccinated individuals, and the size of the outbreaks does not decrease sufficiently with a third booster to make economic sense. This recommendation relies on continuous efforts to maintain high levels of vaccination uptake.

Parametric overdispersed frailty models for current status data

Frailty models have a prominent place in survival analysis to model univariate and multivariate time-to-event data, often complicated by the presence of different types of censoring. In recent years, frailty modeling gained popularity in infectious disease epidemiology to quantify unobserved heterogeneity using Type I interval-censored serological data or current status data. In a multivariate setting, frailty models prove useful to assess the association between infection times related to multiple distinct infections acquired by the same individual. In addition to dependence among individual infection times, overdispersion can arise when the observed variability in the data exceeds the one implied by the model. In this article, we discuss parametric overdispersed frailty models for time-to-event data under Type I interval-censoring, building upon the work by Molenberghs et al. (2010) and Hens et al. (2009). The proposed methodology is illustrated using bivariate serological data on hepatitis A and B from Flanders, Belgium anno 1993-1994. Furthermore, the relationship between individual heterogeneity and overdispersion at a stratum-specific level is studied through simulations. Although it is important to account for overdispersion, one should be cautious when modeling both individual heterogeneity and overdispersion based on current status data as model selection is hampered by the loss of information due to censoring.

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.

Correlated infections: quantifying individual heterogeneity in the spread of infectious diseases

In this paper, we propose new methods for investigating the extent of heterogeneity in effective contact rates relevant to the transmission of infections. These methods exploit the correlations between ages at infection for different infections within individuals. The methods are developed for serological surveys, which provide accessible individual data on several infections, and are applied to a wide range of infections. We find that childhood infections are often highly correlated within individuals in early childhood, with the correlations persisting into adulthood only for infections sharing a transmission route. We discuss 2 applications of the methods: 1) to making inferences about routes of transmission when these are unknown or uncertain and 2) to estimating epidemiologic parameters such as the basic reproduction number and the critical immunization threshold. Two examples of such applications are presented: elucidating the transmission route of polyomaviruses BK and JC and estimating the basic reproduction number and critical immunization coverage of varicella-zoster infection in Belgium, Italy, Poland, and England and Wales. We speculate that childhood correlations stem from confounding of different transmission routes and represent heterogeneity in childhood circumstances, notably nursery-school attendance. In contrast, it is suggested that correlations in adulthood are route-specific.

Role of genetic and environmental factors in British twins with inflammatory bowel disease

BACKGROUND

Twin studies provide insight into the complex interaction between genetic and environmental factors in the development of inflammatory bowel disease (IBD). We assessed associations between childhood environmental factors and development of Crohn's disease (CD) and ulcerative colitis (UC) in twins.

METHODS

Questionnaires on clinical demographics and exposure to environmental factors were sent to twins with IBD, their healthy co-twins, and their doctors. Kappa statistics were used to examine agreement between twin pairs and odds ratios were calculated by conditional logistic regression.

RESULTS

In all, 250 IBD twin pairs (122 CD; 125 UC; 3 CD/UC; 28 concordant pairs) were analyzed. Concordant monozygotic twins with CD showed good agreement for disease location (κ 0.88; 95% confidence interval [CI]: 0.45-1.00), disease behavior (κ 1.00; 95% CI: 0.43-1.00), and moderate agreement for age at diagnosis and need for medical and surgical therapy. Concordant monozygotic twins with UC showed good agreement for disease extent (κ 0.60; CI 0.13-1.00) and use of thiopurines (κ 0.73; CI 0.10-1.00). In discordant twins, symptomatic childhood mumps infection (odds ratio [OR], 3.8; 95% CI, 1.2-11.3) and oral contraceptives (OR, 4.0; 1.1-14.2) were associated with CD. Smoking was associated with CD (OR, 4.3; 95% CI, 1.9-9.8) but inversely associated with UC (OR, 0.3; 95% CI, 0.1-0.9). Both CD and UC twins had suffered more "gastroenteritis" and spent more time with animals than their co-twins.

CONCLUSIONS

Disease phenotype in CD and disease extent in UC appeared to be genetically influenced. Smoking is a risk factor for CD but is protective for UC. Early exposure to "infections" during childhood may be associated with the development of IBD.

Effect of weather variability on the incidence of mumps in children: a time-series analysis

The increasing international interest in the potential health effects of climate change has emphasized the importance of investigations into the relationship between weather variability and infectious diseases. However, few studies have examined the impact of weather variability on mumps in children, despite the fact that children are considered particularly vulnerable to climate change. We acquired data about cases of mumps in children aged <15 years and weather variability in Fukuoka, Japan from 2000 to 2008, and then used time-series analyses to assess how weather variability affected mumps cases, adjusting for seasonal variations, inter-annual variations, and temporal variations of two large epidemics in 2001 and 2004-2005. The weekly number of mumps cases increased by 7·5% (95% CI 4·0-11·1) for every 1°C increase in average temperature and by 1·4% (95% CI 0·5-2·4) for every 1% increase in relative humidity. The percentage increase was greatest in the 0-4 years age group and tended to decrease with increasing age. The number of mumps cases in children increased significantly with increased average temperature and relative humidity.

Measures of disassortativeness and their application to directly transmitted infections

We propose a measure of disassortativeness to summarize contact patterns relevant to the transmission of directly transmitted infections. We discuss the properties of this measure, describe standardization relative to homogeneous mixing, and generalize it to multivariate contact structures. We explore some of its properties and apply our methods to serological surveys of close contact infections and surveys of self-reported social contacts obtained in several European countries.

Age-stratified prevalences of pneumococcal-serotype-specific immunoglobulin G in England and their relationship to the serotype-specific incidence of invasive pneumococcal disease prior to the introduction of the pneumococcal 7-valent conjugate vaccine

Recent changes to the childhood immunization schedule in the United Kingdom have resulted in the inclusion of the 7-valent pneumococcal conjugate vaccine. However, the seroprevalence of pneumococcal antibodies in the population was unknown. To address this, we measured pneumococcal, age-specific immunoglobulin G (IgG) concentrations specific for nine serotypes by an assay run on the Bioplex platform, using 2,664 serum samples collected in England from 2000 to 2004. The lowest concentrations of IgG specific to all serotypes and the proportions of serotype-specific IgG concentrations of >/=0.35 microg/ml were observed in children aged <1 year. From 1 year on, there was a general increase in antibody levels with increasing age, and they remained high in adults. Maternal antibody was detected in young children aged <36 days but waned rapidly. Comparison of the age-specific seroprevalence of serotype-specific IgG to the serotype-specific incidence of invasive pneumococcal disease demonstrated a general inverse relationship for all age groups except the elderly. These data provide a baseline for natural immunity to the pneumococcal serotypes analyzed prior to the introduction of pneumococcal conjugate vaccine in the United Kingdom.

Prevalence of IgG antibody against measles, mumps and rubella in bangladeshi children: a pilot study to evaluate the need for integrated vaccination strategy

The present study was carried out to determine the seroprevalence of IgG antibodies in Bangladeshi children against measles (irrespective of vaccination status), mumps and rubella (MMR) to assess strategic need of combined vaccination for these diseases. A total of 456 children of 1 month to 15 years, were studied. Serum IgG antibodies against MMR were measured by enzyme-linked immunosorbent assay (ELISA). By 3 months, protective IgG antibody level (>40 AU for measles and mumps and >15 IU/ml for rubella) for the diseases found to be between 50% and 80% among the studied children. Protective measles antibody (IgG) was not detected in all the children of 3-9 months and significant number of children between 9 months and 5 years were unprotected (87-65%; P < 0.001). Moreover, children of 3-15 months had no protective antibody level against mumps and significant number of children between 15 months and 5 years were unprotected (92-71%; P < 0.001). Between 5 and 15 years of age, significant number of children became protective (63-85%, P < 0.001). Although, a majority of children between 3 months and 5 years had shown to have no protective antibody against rubella (89-71%; P < 0.01-0.001) between >10 and 15 years 71% children had protective level of antibodies (P < 0.001). No significant difference was observed in antibody prevalence regarding socioeconomic classes, nutritional status and parental education. The data showed that: (i) a significant number of children remain unprotected against MMR in childhood and (ii) an extensive nationwide survey is required to suggest an integrated vaccination strategy in order to implement appropriate control measures of the three infectious diseases.

Mumps in Poland since 1990 to 2003; epidemiology and antibody prevalence

The annual incidence of mumps in Poland over the period 1990-2003 was 45-570 per 100,000 population with the epidemic peak every 4-5 years. Till 2003, mumps vaccination has not been included in the part of National Immunisation Program in Poland that comprises the obligatory vaccinations. However, mumps vaccination was recommended by National Health Authority for children at the second year of life and it could be obtained privately. The proportion of vaccinated children has increased by 50% in last years. It has influenced on decreasing of number of notified mumps cases in Poland, on lengthening of inter-epidemic period as well as on drift of infections towards older groups of children. The results of serological survey carried out on 1390 serum samples have indicated, that the proportion of positive serum samples (>11 VE/ml) was only 24.1% for children aged 1-4 years, 45.4% for children aged 5-9 years, 72.5% for age group 10-14 years, and over 85% for persons aged 15-30 years. Epidemiological data and the high proportion of individuals with negative titres of specific mumps IgG antibodies justify the need of introduction of obligatory mass immunisation against mumps in Poland.

Seroepidemiology of group C rotavirus infection in England and Wales

A total of 3199 serum samples collected in 1993--1994 from two population cohorts from England and Wales were tested for the prevalence of IgG antibodies specifically directed against group C rotavirus VP6. Seroprevalence was 39% (95% confidence intervals: 37.0-40.4%). Seroprevalence was highest (46.0%) in the oldest age group (61-70 years of age). Infection with group C rotaviruses occurred at an earlier age and with higher incidence in rural than in urban populations. These results may suggest transmission from animals to humans, however further work is required to identify the reservoir of group C rotavirus for human infection.

Time-resolved fluorometric immunoassay for rubella antibody--a useful method for serosurveillance studies

Rubella antibody (IgG) has been measured in females reporting for antenatal screening using single radial haemolysis (SRH) and time-resolved fluorescence immunoassay (TRFIA). We have shown TRFIA to be a simple, specific, highly sensitive, quantitative assay for rubella IgG with a lower limit of detection of 0.2IU/ml. Out of 506 sera tested by SRH, 18 (3.6%) had low levels of antibody (< 15IU/ml) compared to 83 (16.4%) tested by TRFIA and, of these, 32 (6.3%) had rubella antibody concentrations < 10IU/ml. The lowest level (3.1%) of rubella susceptibility (antibody levels < 10IU/ml) was found in females aged 25-29 and the highest level of susceptibility (23.5%) occurred in females aged 40 years, and over. Geometric mean rubella antibody concentrations (IU/ml) were 26.8, 34.4, 34.8, 29.7, 27.5 and 20.0 for age groups <20, 20-24, 25-29, 30-34, 35-39 and > or =40 years, respectively. Our rubella vaccination policies have built up good levels of rubella immunity in women of childbearing age in our locality, and using TRFIA technology we can accurately monitor changes over time.

Vaccine programmes and policies

Management of an effective national vaccine strategy necessitates careful planning. In the face of budgetary constraints and the likely development of many new vaccines over the next few years, a rational choice of which vaccines to use and how best to use them will depend on first class disease surveillance, economic analysis of cost effectiveness and mathematical modelling to ensure optimal vaccine delivery. Effective immunisation programmes require strategic planning that integrates the outputs of these parameters with available health facilities with the least possible disruption. At the present time, the greatest threat to vaccination is resistance to continuing vaccination in the face of declining prevalence of many infectious diseases and heightened fears over vaccine safety. Re-assurance of the public that vaccines are safe demands effective detection of vaccine-related side-effects and rigorous investigation of any safety concerns.

The burden of infection with HSV-1 and HSV-2 in England and Wales: implications for the changing epidemiology of genital herpes

OBJECTIVE

To measure the burden of infection with herpes simplex type 1 (HSV-1) and herpes simplex type 2 (HSV-2) in the general population of England and Wales and to assess temporal changes in the incidence of HSV-1 infection in childhood.

METHODS

4930 residual blood samples taken from people aged 0-69 years and submitted to 15 public health laboratories in England and Wales between January 1994 and June 1995, and 500 samples taken from people aged 10-14 years between November 1986 and December 1987, were screened for IgG antibody to HSV-1 and HSV-2 using type specific ELISA assays.

RESULTS

The prevalence of antibody to HSV-1 in 10-14 year olds declined from 34% in samples collected in 1986-7 to 24% in samples collected in 1994-5 (p < 0.001). HSV-1 antibody prevalence in adults increased with age and was higher in females than males, reaching 54% in females aged 25-30 years in 1994-5. In samples collected in 1994-5 from people aged 16-69 years HSV-2 antibody was detected in sera from 3.3% of men and 5.1% of women.

CONCLUSIONS

The incidence of HSV-1 infection in childhood is falling in England and Wales. The prevalence of HSV-2 infection in the general population is low, with the rate of infection significantly lower than that described for the general population in the United States and developing countries. The falling rate of HSV-1 infection in childhood may be one factor contributing to the increasing incidence of genital HSV-1 infection.

Maternal rubella-specific antibody prevalence in Ethiopian infants

In countries with a high transmission rate of rubella the optimal age for universal rubella vaccination of infants is critically dependent upon the rate of loss of maternal antibodies. Few studies have investigated the decay characteristics of such antibodies. Mother:infant pairs were recruited at the Ethio-Swedish Children's Hospital, Addis Ababa, in 1994/95. Rubella antibody levels, determined by radial haemolysis, were available for analysis from 1542 infants aged 0-12 months, with 942 repeat measures, and from 846 mothers. Decay in seropositivity was well described by a delayed exponential function. The proportion seropositive at age 6, 9, or 12 months was 6-13%, 1-4%, or 0-1%, respectively, dependent upon assay cutoff level. Only infant age and mother's antibody level were important predictors of seropositivity. Results suggest that the success of vaccination at age 9 months or above would be little affected by residual maternal antibodies.

Ten years of serological surveillance in England and Wales: methods, results, implications and action

BACKGROUND

The first age-stratified serological survey of antibody to measles, mumps and rubella in the UK was conducted in 1986/87 prior to the introduction of MMR vaccine into the immunization programme. Serum collection and testing have continued annually, allowing trends over time to be monitored. These sera have also been available for ad hoc surveys of other infections.

METHODS

Residual sera are collected in participating laboratories and sent to a central store where they are irrevocably unlinked from identifying data. A unique identity number is assigned to each serum and details of age and sex are collated on a database. The sera are accessed for testing as required.

RESULTS

The results of recurring and other surveys performed over the last ten years are presented. These demonstrate that opportunistic serum samples are an ideal resource for serological surveillance programmes.

CONCLUSIONS

The serological surveillance programme has provided past exposure profiles for many infections. These data have resulted in a number of national policy changes and have been instrumental in shaping the UK vaccination programme.

Serum levels of measles IgG antibody activity in children under 5 years in Dar-es-Salaam, Tanzania

Measles IgG antibody levels were estimated in sera from 685 Tanzanian children, 374 (54.6%) boys and 311 (45.4%) girls aged 18 months to 5 years, using an enzyme-linked immunosorbent assay (ELISA). The children were screened for HIV-1 and 2 antibodies using ELISA, and reactive sera were confirmed by Western blot. Nutritional status was assessed by anthropometry. Overall measles vaccination coverage was 98.8%. Measles antibody activity was not detected in 41 (6.0%) children, and ten (1.5%) had antibody levels below 200 mIU/ml, the cut-off level considered to be protective. The non-reactive samples were from one unvaccinated child, one child with unknown vaccination status and 39 vaccinated children. Measles IgG antibody levels were higher in girls (3452.1 mIU/ml) than in boys (2928.2 mIU/ml) (p = 0.02). Higher mean levels were found in children with a history of low birthweight (< 2.5 kg) (p = 0.03). There were no significant differences in measles antibody levels with regard to variations in nutritional status. No correlation (r2 = 0.002) was found between antibody levels and time elapsed since vaccination. In a multivariable logistic regression analysis, children who were HIV-seropositive (n = 9) were more likely to have non-protective antibody levels < 200 mIU/ml (OR = 5.85; 95% CI: 1.37-24.93).

Measles immunity and vaccination policy in Catalonia

The prevalence of antibodies against measles in a representative sample of the school population in Catalonia was established and the results compared with previous studies. The study was carried out in 1996 using blood samples obtained from schoolchildren aged 6-7 years, 10-11 years, 13 14 years and 15-16 years. 1231 schoolchildren were studied. The global prevalence of antibodies was 96.3%, and a considerable increase was observed with respect to the prevalence in 1986 (89.4%). The level of antibodies was 94% at 6-7 years and 10-11 years, 99.7% at 13-14 years and 98.3% at 15 16 years. These data would suggest the advancement of the administration of the second dose of measles-mumps rubella vaccine to 4 6 years instead of at 11 years.

An evaluation of nine commercial EIA kits for the detection of measles specific IgG

Nine commercial EIAs for measles-specific IgG were compared with haemagglutination inhibition (HI) and plaque reduction neutralization (PRN). A total of 174 sera selected, to give approximately half of the sera without measles antibody by HI, were tested by all EIAs and HI. However, there was sufficient volume of only 101 samples for testing by PRN. A dilution curve of the British Standard measles antibody serum was also tested by each EIA. Assays were evaluated qualitatively against a consensus EIA result, HI and PRN: Gull, Melotest and Behring EIAs performed best. Quantitative evaluation was by assessment of the characteristics of the standard dilution curve, and by plotting differences with PRN against mean: Gull and Melotest EIAs were best.

Anti-Toxoplasma gondii immunoglobulins A and G in human saliva and serum

Paired human saliva and serum samples from 60 individuals were tested for specific IgA and IgG antibodies to Toxoplasma gondii. The study in both fluids was carried out by indirect immunoenzymatic assay (ELISA). Saline antigenic extract of T. gondii was used to coat plastic surfaces upon which the samples were then incubated; monospecific conjugates of anti-IgA and anti-IgG-peroxidase were then incubated with the samples after a washing procedure to separate the unbound antibodies. The enzymatic activity was measured and the results expressed in terms of ELISA index. Toxoplasma-specific IgG antibodies were detected in 43 of the serum samples (71.7%) and in 12 of the saliva samples (20.0%) whereas Toxoplasma-specific IgA antibodies were detected in 18 of the serum samples (30.0%) and in 12 of the saliva samples (20.0%). No association was observed when the Toxoplasma-specific IgG reactive and non-reactive serum samples were compared with the reactive and non-reactive saliva samples for this class of immunoglobulin. On the other hand, a significant association was observed when the Toxoplasma-specific IgA reactive and non-reactive serum samples were compared with the reactive and non-reactive saliva for this type of antibody. In conclusion, our results show that the detection of salivary IgA reflects the serum level of this isotype but salivary IgG does not. Moreover, the isolated detection of salivary IgG may not contribute to epidemiological studies of chronic toxoplasmic infections.

Control of rubella and congenital rubella syndrome (CRS) in developing countries, Part 2: Vaccination against rubella

In 1995-96 we conducted a review of rubella immunization strategies. Worldwide, 78 countries (more than one-third) reported a national policy of using rubella vaccine. This was closely related to country economic status. Based on the United Nations country classification, rubella vaccine is used in 92% of industrialized countries, 36% of those with economies-in-transition, and 28% of developing countries. Cases of congenital rubella syndrome (CRS) may be prevented as follows: by providing direct protection to women and/or schoolgirls (a selective vaccination strategy); by vaccinating boys and girls to provide indirect protection by reducing the transmission of rubella virus (a childhood vaccination strategy); or by a combination of these approaches (a combined strategy). A combined strategy was most commonly reported (60% of countries); seven countries (9%) reported a selective strategy; and 24 countries (31%) reported only childhood immunization. Experience has shown that it is essential to include vaccination of women of childbearing age in any rubella control strategy. Childhood vaccination alone may pose a risk of an increase in CRS cases. Although many countries have introduced rubella vaccine, few report any data on the impact of vaccination. Countries using rubella vaccine need to establish surveillance for rubella and CRS and monitor coverage in each of the target groups.

Interpretation of serological surveillance data for measles using mathematical models: implications for vaccine strategy

Serological surveillance of measles immunity has been carried out in England since 1986/7. Results from sera collected in 1989-91 revealed that the proportion of school age children who were susceptible to measles was increasing, following the introduction of the measles, mumps and rubella vaccination programme in October 1988. Mathematical models are used to interpret these data and determine whether this increasing susceptibility is sufficient to allow a resurgence of disease from the low levels achieved by 1993. The models summarize serological profiles by a single parameter, the reproduction number R, which quantifies the level of herd immunity in the population. Results showed that there was cause for concern over the levels of susceptibility to measles, with an epidemic of over 100,000 cases likely in 1995/6. These predictions are consistent with trends in the incidence and age distribution of measles and have enabled the planning of a major vaccination campaign.

Reasons for non-uptake of measles, mumps, and rubella catch up immunisation in a measles epidemic and side effects of the vaccine

OBJECTIVE

To investigate the reasons for poor uptake of immunisation (non-immunisation) and the possible side effects of measles, mumps, and rubella vaccine in a catch up immunisation campaign during a community outbreak of measles.

DESIGN

Descriptive study of reasons for non-immunisation and retrospective cohort study of side effects of the vaccine.

SETTING

Secondary schools in South Glamorgan.

SUBJECTS

Random cluster sample of the parents of 500 children targeted but not immunised and a randomised sample of 2866 of the children targeted.

MAIN OUTCOME MEASURES

Reasons for non-immunisation; symptoms among immunised and non-immunised children.

RESULTS

Immunisation coverage of the campaign was only 43.4% (7633/17,595). The practical problems experienced included non-return of consent forms (6698/17,595), refusal of immunisation (2061/10,897 forms returned), and absence from school on day of immunisation (1203/8836 children with consent for immunisation). The most common reasons cited for non-immunisation were previous measles infection (145/232), previous immunisation against measles (78/232), and concern about side effects (55/232). Symptoms were equally common among immunised and non-immunised subjects. However, significantly more immunised boys than non-immunised boys reported fever (relative risk 2.31 (95% confidence interval 1.36 to 3.93)), rash (2.00 (1.10 to 3.64), joint symptoms (1.58; 1.05 to 2.38), and headache (1.31 (1.04 to 1.65)).

CONCLUSIONS

Many of the objections raised by parents could be overcome by emphasising that primary immunisation does not necessarily confer immunity and that diagnosis of measles is unreliable. Measles, mumps, and rubella vaccine is safe in children aged 11-15.

Predicting the impact of measles vaccination in England and Wales: model validation and analysis of policy options

Measles incidence in England and Wales has fallen to an all-time low. Attention is now focused on preventing local outbreaks, and, in the long run, on the elimination of indigenous measles. A realistic age-structured (RAS) mathematical model of measles transmission is used to reconstruct the impact of measles vaccination in England and Wales from 1968 to the present and to evaluate the merits of future policy options. In general, the predictions of the model show good agreement with long-term age stratified case reports and seroprevalence surveys. The model underestimates the proportion of cases that are notified in 0-2-year-old children. However, recent work suggests a high degree of misdiagnosis in this age group. Projections on the basis of the existing vaccination strategy in the UK suggest that the present level of measles vaccine coverage will be insufficient to eliminate small seasonal outbreaks of measles. This result is, however, sensitive to the assumed level of vaccine efficacy. Explorations of a variety of changes to current vaccination strategy favour a 2-dose schedule with the second dose administered at age 4 years irrespective of vaccination history. A vaccination campaign in school-age children, to reduce deficits in herd immunity, would accelerate progress towards measles elimination.

[Mumps epidemiology--worldwide]

Mumps is an acute viral infection that is endemic worldwide and that occurs primarily in school-age children and adolescents. The most prominent manifestation is tender swelling of the parotid gland. The course of the disease is usually mild and selflimited. Meningitis and orchitis, the latter more common in postpubertal persons, are less frequent manifestations of this disease. As characteristic of many viral infections the severity of the illness increases with age. In the present review first the most important epidemiologic parameters of mumps are presented, as well as the various clinical manifestations and complications. Further the epidemiology of mumps in developing and in industrialized countries is discussed. Breakthrough infections with mumps occurring with either low or high vaccination coverage are described.

Salivary antibody detection in epidemiological surveys: a pilot study after a mass vaccination campaign against rubella in São Paulo, Brazil

The sensitivity and specificity of salivary rubella antibody detection was investigated using samples collected from 301 children after a mass vaccination campaign in the state of São Paulo, Brazil. Saliva samples were collected by 2 different methods: directly dribbling into a container or using a commercial collecting device. Corresponding finger-prick blood samples were collected on filter paper. Rubella specific immunoglobulin G (IgG) was measured in saliva by antibody capture radioimmunoassay and in blood samples by indirect enzyme-linked immunosorbent assay. The detection of salivary rubella specific IgG showed good correlation with the detection of rubella antibody in the blood samples. For both collecting techniques the predictive value for a positive saliva test was > 99% compared with the results from the blood tests. However, the predictive value for a negative saliva test was only 58.3% for a dribbled sample, compared to 100% for saliva collected using the commercial device. Moreover, collecting saliva by dribbling from children less than 4 years old was difficult. The detection of rubella specific IgG in saliva collected using a commercial device proved to be sensitive and specific in this epidemiological study, encouraging its more widespread application as a means of surveillance after mass vaccination.

Some bounds on estimates for reproductive ratios derived from the age-specific force of infection

In this paper we shall look at estimation of reproductive ratios for common childhood infections such as chickenpox, measles, mumps, and hepatitis A with and without a vaccination program. The paper starts with a survey of previous work in this area. We suppose that we are given data in the form of an age-related serological profile with a given vaccination program. This is used to estimate the reproductive ratio and evaluate vaccination campaigns. The effect of different mixing patterns, such as homogeneous mixing, assortative mixing, proportional mixing, and symmetric mixing are discussed. R phi denotes the reproductive ratio when a steady-state vaccination campaign phi is used. Assortative mixing maximizes the reproductive ratio R phi. A mixing pattern which minimizes R phi and a lower bound for R phi for the important symmetric mixing case are found. The most usual situation is that we are given the age-serological profile with no vaccination so that we have bounds for the basic reproductive ratio R0. These results are illustrated with an application to vaccination against hepatitis A in Bulgaria. Numerical evaluations of the effect of different elimination vaccination strategies are examined.

Outbreak of measles in a teenage school population: the need to immunize susceptible adolescents

An outbreak of measles occurred in a community school and the surrounding area in Crowborough, East Sussex, UK, from December 1992 to February 1993. There were 96 suspected cases reported: 66 cases among 1673 students at one school and 30 community cases. The majority of suspected cases were in those aged 11-17 (78%), 2 cases occurred in infants < 1 year old and 8 cases in adults aged 18 years or over. Data collected on 60 (91%) of the 66 suspect school cases showed 56 (93%) had an illness which met a case definition of measles. Eighteen had confirmatory IgM measles antibody. Two cases were hospitalized. The local percentage uptake for measles immunization for the school age years affected varied between 64% and 84%. A survey of parents showed that approximately 74% of the students attending the school had a history of measles immunization. The immunization rates reported by parents for children who developed measles was 21%, (29% based on GP records) compared with 77% for those who remained well. Vaccine efficacy was estimated to be 92%. This outbreak, along with others recently reported in older unimmunized children in the UK, reinforces the need for catch-up immunization programmes to reach this susceptible group of adolescents.

Risk of aseptic meningitis after measles, mumps, and rubella vaccine in UK children

Cases of aseptic meningitis associated with measles/mumps/rubella vaccine were sought in thirteen UK health districts following a reported cluster in Nottingham which suggested a risk of 1 in 4000 doses, substantially higher than previous estimates based on cases reported by paediatricians (4 per million). Cases were ascertained by obtaining vaccination records of children with aseptic meningitis diagnosed from cerebrospinal fluid samples submitted to Public Health Laboratories or discharged from hospital with a diagnosis of viral meningitis. Both methods identified vaccination 15-35 days before onset as a significant risk factor and therefore indicative of a causal association. With both, half the aseptic meningitis cases identified in children aged 12-24 months were vaccine-associated with onset 15-35 days after vaccine. The study confirmed that the true risk was substantially higher than suggested by case reports from paediatricians, probably about 1 in 11,000 doses. However, the possibility that the aseptic meningitis induced by vaccination was largely asymptomatic and a chance laboratory finding in children investigated for other clinical conditions, particularly febrile convulsions, could not be excluded. Comparison of national reports of virus-positive mumps meningitis cases before and after the introduction of this vaccine indicated that the risk from wild mumps was about 4-fold higher than from vaccine. Altogether, 28 vaccine-associated cases were identified, all in recipients of vaccines containing the Urabe mumps strain. The absence of cases in recipients of vaccine containing the Jeryl Lynn strain, despite its 14% market share, suggested a higher risk from Urabe vaccine. A prospective adverse event surveillance system using the study methods is currently being established to assess the risk, if any, from the Jeryl Lynn strain which is now the only mumps vaccine used in the UK.

The age of infection with varicella-zoster virus in St Lucia, West Indies

Sera from an age-stratified sample of 1810 people from the Caribbean island of St Lucia were tested for antibodies against varicella-zoster virus. The results indicate that very few infections occur in childhood, which agrees with clinical survey data from other tropical countries, but contrasts with the observed high case rate in children in temperate countries. The alternative hypotheses which may explain these results are discussed, and it is suggested that high ambient temperatures interfere with the transmission of the virus. Irrespective of the cause, the pattern of varicella incidence observed has important implications for any vaccination policy adopted in tropical countries.

Prevalence of antibodies to Norwalk virus in England: detection by enzyme-linked immunosorbent assay using baculovirus-expressed Norwalk virus capsid antigen

A total of 3,250 serum specimens collected in England in 1991 and 1992 were tested by an indirect enzyme-linked immunosorbent assay for antibody to Norwalk virus using baculovirus-expressed capsid antigen, and 2,382 (73.3%) were positive. The prevalence of Norwalk virus antibody differed regionally. It was lowest (24.6%) in 6- to 11-month-old infants and increased to 89.7% in persons over 60 years old.

Measles outbreak in Fife: which MMR policy?

The introduction of measles, mumps and rubella vaccine (MMR) into the United Kingdom childhood immunisation schedule has resulted in a substantial reduction in the incidence of all three diseases. None the less, there have recently been outbreaks of measles in parts of the country which have a record of high MMR uptake among young children. In these outbreaks it is mainly older children who have been affected. This report documents such an outbreak in Fife, an area with a very high MMR uptake among two-year-old children (96%). The current policy of giving MMR vaccine only once to children at 15 months of age may not be sufficient to enable the United Kingdom to achieve the WHO target of measles elimination by the year 2000. Other possible strategies to achieve this objective are discussed.

Vaccine safety versus vaccine efficacy in mass immunisation programmes

In community-wide immunisation programmes against childhood infections there is a conflict between the interests of the individual (vaccine safety and efficacy) and the interests of the community (vaccine uptake and level of herd immunity). Studies suggesting that the complication rate is greater with the high efficacy Urabe Am 9 mumps vaccine than with the lower efficacy Jeryl Lynn vaccine, have led to concern about whether the higher efficacy mumps vaccine should be introduced or retained in nationwide mass immunisation programmes. We describe the use of a mathematical model to assess benefits and risks to both individual and community, and illustrate this method by reference to immunisation programmes based on these vaccines. On the basis of current epidemiological data on viral transmission and vaccine coverage in England and Wales, data on vaccine-associated and infection-associated complication rates, and vaccine efficacies estimated from clinical trials, our analyses suggest there is little to choose between the two vaccines, but that overall performance depends on the level of vaccine coverage in a defined population. In community-based programmes, the greater apparent safety of the Jeryl Lynn vaccine (fewer vaccine-induced complications) is offset by the greater apparent efficacy of the Urabe Am 9 vaccine (fewer complications due to natural infection). The findings suggest that it may not always be in the interests of the community to use the vaccine with the lowest complication rate.

Rubella in Europe

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Rubella in the United Kingdom

The first description of rubella in the UK was by an English physician, Dr William Maton, who reported an outbreak of an illness resembling a mild form of scarlatina in a boys' public school in 1815 [1]. Some years later, when observing the spread of a rash-associated illness in a large family, Maton described the characteristic clinical features of rubella, namely a mild prodromal illness followed by a generalized and often tingling rash lasting for a few days and associated with enlarged and tender glands in the occipital and postauricular regions. He also correctly identified the relatively long incubation period of rubella and noted the absence of fever and other signs of constitutional upset. Maton did not suggest an English name for this disease which had been previously described and called Rothëln by German physicians in the late 18th century. The term ‘rubella’ (Latin for ‘little red’) was first used in 1866 by another English physician, Dr Henry Veale, when describing an outbreak of Rothëln in a boys' school in India [2].

Acute infectious erythemas in children: a clinico-microbiological study

One-hundred children with an acute illness comprising fever and widespread erythematous rash were prospectively studied to determine whether clinical presentations are helpful in defining the causative agent and to identify the most appropriate microbiological specimens. An infectious agent was identified in 65 children; 72% were viruses, 20% were bacteria, 5% were Mycoplasma pneumoniae and in 3% both viruses and bacteria were detected. The most common infectious agents were picornaviruses, an atypical presentation of measles and Group A beta-haemolytic Streptococcus. Different patterns of rash occurred with each of these infections. The clinical presentation of a child with an acute febrile illness and rash was unhelpful in defining the causative agent. Routine management should include a throat swab for bacterial investigation and in selected cases a blood sample for IgM viral titres.

Mumps vaccination of young adults is unwarranted

A clinical and epidemiological study of mumps was carried out over a 18-month period and included 104 soldiers (61% of the reported cases in the Israel Defence Forces). The average number of days off work was 12.9 +/- 9.2 days. The most common complication was orchitis (19/72 men; 26%), followed by 3 cases of pancreatitis (3%) and 2 cases of meningitis (2%). 13 men with orchitis were tested, and all had normal spermograms. No long term important sequelae were described. The transmission rate was low with no respondent reporting more than one secondary case among soldiers serving in the same unit. The socio-economic level of mumps patients was comparable to that of the general army population at the time of the study. Our data do not support a mass immunization program of the adult population.