A study of maternally derived measles antibody in infants born to naturally infected and vaccinated women

Seroprevalence of Measles in Pairs of Mothers and Newborns in Southern Greece

Maternal immunoglobulin G (IgG) antibodies that are passively transferred to newborns through the placenta confer protection if they are exposed to measles virus. A measles outbreak occurred in several European countries including Greece, between 2016 and 2018. A prospective study was conducted in the General Hospital of Lakonia, regarding the measles seropositivity status of mother and newborn pairs. IgG antibody titer for measles was measured in serum samples acquired from pairs of mothers and newborns. The samples were analyzed through quantitative enzyme-linked immunosorbent assay, and antimeasles IgG >200 IU/mL was considered to be protective. Demographic data for mothers and neonates and data regarding immunization status of mothers were analyzed. Study population included 206 mothers and their newborns. In total, 12.6% of mothers (n = 26) and 10.7% of newborns (n = 22) did not have protective serology. A statistically significant positive linear association between maternal and neonatal antibodies was found (rho = 0.924) (p = 0.001). Neonates whose mothers were seropositive had higher antibodies [geometric mean concentration (GMC): 804.8 (728.3-889.2)] than neonates whose mothers were seronegative/borderline [GMC: 97.7 (64.2-148.8)] (p = 0.001). In the study area, a significant rate of mothers and newborns was found to have nonprotective measles serology that exceeds the limit required for herd immunity. Vaccination coverage in women of reproductive age should be increased to reduce potential for future measles epidemics.

Measles susceptibility in maternal-infant dyads-Bamako, Mali

Measles is endemic in Africa; measles mortality is highest among infants. Infant measles antibody titer at birth is related to maternal immune status. Older mothers are likelier to have had measles infection, which provides higher antibody titers than vaccine-induced immunity. We investigated the relationship between maternal age and measles susceptibility in mother-infant pairs in Mali through six months of infancy. We measured serum measles antibodies in 340 mother-infant pairs by plaque reduction neutralization test (PRNT) and calculated the proportion of mothers with protective titers (>120 mIU/mL) at delivery and the proportion of infants with protective titers at birth, and at three and six months of age. We explored associations between maternal age and measles antibodies in mothers and infants at the timepoints noted. Ten percent of Malian newborns were susceptible to measles; by six months nearly all were. Maternal and infant antibody titers were highly correlated. At delivery, 11% of mothers and 10% of newborns were susceptible to measles. By three and six months, infant susceptibility increased to 72% and 98%, respectively. Infants born to younger mothers were most susceptible at birth and three months. Time to susceptibility was 6.6 weeks in infants born to mothers with measles titer >120-<430 mIU/mL versus 15.4 weeks when mothers had titers ≥430 mIU/mL. Maternal and newborn seroprotective status were positively correlated. Improved strategies are needed to protect susceptible infants from measles infection and death. Increasing measles immunization coverage in vaccine eligible populations, including nonimmune reproductive-aged women and older children should be considered.

The half-life of maternal transplacental antibodies against diphtheria, tetanus, and pertussis in infants: an individual participant data meta-analysis

AIM

There are few reliable estimates of the half-lives of maternal antibodies to the antigens found in the primary series vaccines. We aimed to calculate the half-lives of passively acquired diphtheria, tetanus and pertussis (DTP) antibodies in infants. We aimed to determine whether decay rates varied according to country, maternal age, gestational age, birthweight, World Bank income classifications, or vaccine received by the mother during pregnancy.

METHODS

De-identified data from infants born to women taking part in 10 studies, in 9 countries (UK, Belgium, Thailand, Vietnam, Canada, Pakistan, USA, Guatemala and the Netherlands) were combined in an individual participant data meta-analysis. Blood samples were taken at two timepoints before any DTP-containing vaccines were received by the infant: at birth and at 2-months of age. Decay rates for each antigen were log₂-transformed and a mixed effects model was applied. Half-lives were calculated by taking the reciprocal of the absolute value of the mean decay rates.

RESULTS

Data from 1426 mother-infant pairs were included in the analysis. The half-lives of the 6 antigen-specific maternal antibodies of interest were similar, with point estimates ranging from 28.7 (95% CI: 24.4 - 35) days for tetanus toxoid antibodies to 35.1 (95% CI: 30.7 - 41.1) days for pertactin antibodies. The decay of maternal antibodies did not significantly differ by maternal age, gestational age, birthweight, maternal vaccination status or type of vaccine administered.

CONCLUSION

Maternal antibodies decay at different rates for the different antigens; however, the magnitude of the difference is small. Decay rates are not modified by key demographic or vaccine characteristics.

Dynamics of maternally transferred antibodies against measles, mumps, and rubella in infants in Sri Lanka

BACKGROUND

Determining the dynamics of maternally transferred antibodies against measles, mumps, and rubella infections in infants is important for making evidence-based policy decisions regarding the timing of vaccination.

METHODS

The levels of serum immunoglobulin G (IgG) developed against measles, mumps, and rubella infections were assessed using commercial ELISA kits in mother-newborn pairs (n = 294) and 6-12-month-old infants (n = 280) recruited from Colombo District, Sri Lanka. Antibody levels of mothers and their newborns were assessed with respect to sex and parity. Antibody levels and the protection conferred were assessed in a sample of infants who completed 6-12 months of age in relation to their age and sex. Antibody levels were compared between different age and sex groups using the Mann-Whitney U-test, and correlations of antibody titers were performed using the Spearman correlation test.

RESULTS

The prevalence rates of seropositivity for measles, mumps, and rubella were 91.5%, 89%, and 88%, respectively, in mothers, and 95%, 91.5%, and 93%, respectively, in their newborns. The newborns had mean IgG levels exceeding those of the mothers (P < 0.001). Mothers with natural infections had higher antibody levels compared to vaccinated mothers, which resulted in a higher level of maternal transfer. All of the infants who were 9-10 months of age or older were seronegative for measles, all of those who were 10-11 months of age or older were seronegative for rubella, and all of those who were 11-12 months old were seronegative for mumps.

CONCLUSIONS

The maternal transfer of antibodies to newborns is efficient and renders protection until the infants are 6-7 months old in the case of mumps and rubella and 7-8 months old in the case of measles. Hence infants remain vulnerable to infections before the first dose of the MMR vaccine.

Humoral Immunity against Measles in Mother-Infant Pairs during the First Year of Life in Greece: A Cross-Sectional Study

Measles outbreaks have surfaced in Europe during the last decades. Infants <12 months of age were the most severely affected pediatric population. The aim of this study was to investigate the duration of maternally derived measles antibodies in infants aged 1 to 12 months in relation to maternal humoral immune status and other parameters. In a prospective, cross-sectional cohort study, 124 mother/infant pairs and 63 additional infants were recruited from October 2015 through December 2019. Infants were hospitalized in a university pediatric department of a general hospital. Demographic and epidemiological data were recorded and blood samples were collected from mothers and their infants. Commercially available enzyme-linked immunosorbent assay (ELISA) was used for measuring measles antibodies. Fifty nine percent of mothers had vaccine-induced and 15% infection-acquired measles immunity. Eighty-eight percent and 94% of infants were unprotected by 5 and 10 months of age, respectively. Maternal antibody levels and infant age were significant independent predictors of infants’ antibody levels whereas the method of maternal immunity acquisition, age, and origin [Greek/non-Greek] were not. Our findings suggest that about 90% of infants are susceptible to measles beyond the age of 4 months. To our knowledge, these are the first data from Greece reported under the current community composition and epidemiological conditions.

Epidemiological changes in measles infections in southern China between 2009 and 2016: a retrospective database analysis

Background

The incidence rate of measles in China reached a nadir in 2012 after 2 supplementary immunization activities (SIAs) were undertaken in 2009 and 2010. However, the disease began re-emerging in 2013, with a high prevalence rate observed in 2013–2014 in the southern province of Guangdong. In this study, we assessed the changes that occurred in measles epidemiology during 2009–2016, particularly between 2009 and 2011 (when the influence of the SIAs were in full effect) and between 2012 and 2016 (when this influence subsided).

Methods

Data from 22,362 patients with measles diagnosed between 2009 and 2016, and whose diagnoses were confirmed clinically and/or with laboratory testing, were extracted from the National Infectious Disease Monitoring Information System. Descriptive analyses were performed, and changes in epidemiological characteristics between 2009 and 2011 and 2012–2016 were compared.

Results

There was a substantial surge in 0–8-month-old patients after 2012; the incidence rate increased from 4.0 per 100,000 population in 2011 (10.3% of the total) to 280 per 100,000 population in 2013 (32.8% of the total). Patients aged 0–6 years represented 73.4% of the total increase between 2011 and 2013. Compared with 2009–2011, adults aged ≥25 years accounted for a higher proportion of patients in 2013 and after (p < 0.01), and were highest in 2016 (31% of the patient total).

Conclusion

Despite the remarkable results achieved by SIAs in terms of providing herd immunity, the 2013 resurgence of measles revealed insufficient immunization coverage among children. Therefore routine immunization programs should be strengthened, and supplementary vaccinations targeting adults should also be contemplated.

Emergent measles-containing vaccination recommendation for aged 6-11 months and detection of vaccine-associated measles during a large measles outbreak in Okinawa, Japan, in 2018

Okinawa Prefecture, Japan, experienced a large measles outbreak from March to May 2018. During this outbreak, there were 99 laboratory-confirmed cases and 14 vaccine-associated measles cases. In addition to the reinforcement of routine immunization, Okinawa prefectural government introduced emergent measles-containing vaccination recommendations for infants aged 6-11 months as part of the outbreak response. Increased concern exists in Okinawa about measles in infants following a previous outbreak from 1998 to 2001, when nine children including four infants died. Of 8062 infants aged 6-11 months who received measles-containing vaccine (MCV), six developed vaccine-associated measles; incidence was 0.74 per 1000 doses (95%CI 0.27-1.62). This was similar to that of first dose routine immunization recipients at one year of age (IR 0.60, 95%CI 0.20-1.78). Among 14 vaccine-associated measles cases, throat swab samples showed the highest positive rate (92.9%) by real-time reverse transcription polymerase chain reaction (RT-qPCR), followed by urine (25.0%) and whole blood (7.7%) samples. Furthermore, one throat swab sample classified as equivocal by RT-qPCR was positive by conventional RT-PCR (RT-PCR). During an outbreak, it is critical to distinguish between cases with measles-like symptoms caused by wild circulating virus and those caused by vaccine-derived virus as accurately and urgently as possible because the public health response will be quite different. No infant deaths were observed during this outbreak, and no severe adverse events following immunization were seen among infants 6-11 months old who were given MCV as a public health response. Thus, we conclude that introduction of emergent MCV was effective and describing the characteristics of vaccine-associated measles cases during a measles outbreak will be helpful for future outbreak response efforts.

Prevalence of Maternal Measles Antibody and Its Associated Factors among Infants in Coastal Karnataka, India

BACKGROUND

The current recommendation in India to commence first dose of measles immunization is at 9 months of age. The effectiveness of measles vaccination is greatly impacted by the level of maternal measles antibody (MMA) during infancy.

OBJECTIVES

To find the prevalence of MMA and to study the maternal and infant factors associated with persistence of MMA among the infants in a Indian rural community.

METHODOLOGY

Dried blood spot sample was collected before vaccination among infants aged 9 months and above when they came for first dose of measles vaccine to assess measles-specific maternal IgG antibody titers by enzyme immunoassay. Maternal and child factors influencing persistence of MMA were collected by interviewing the mothers. Association between various factors affecting seropositivity was tested using univariate logistic regression analysis and strength of association is reported as risk ratio with 95% confidence interval.

RESULTS

Based on the qualitative estimation among all the recruited children (250) in the study, 4 (1.6%) infants showed the presence of MMA whereas 25 (10%) of children had MMA on quantitative estimation. The effect of maternal factors, child nutrition, and sociodemographic factors on the presence of MMA was not found to be statistically significant.

CONCLUSION

The prevalence of persistent MMA (IgG titer ≥200 mIU/ml) among the infants aged 9-12 months was 10%. The choice of vaccinating infants at the end of 9 months for the first dose of measles vaccine is justified as the remaining (90%) of infants were susceptible for measles infection at this age.

Syndromic surveillance of potentially epidemic infectious diseases: Detection of a measles epidemic in two health centers in Gabon, Central Africa

Measles is a respiratory disease caused by the measles virus (MV) belonging to the Paramyxovirus family and the Morbillivirus genus. Due to a failure in maintaining immunization coverage in some countries, measles is a re-emerging disease in the human population, especially in Africa. The aim of this study was to describe a measles epidemic in Gabon. At first, a syndromic surveillance was set up. Blood samples from febrile patients with maculopapular rash were taken and sent to the measles reference center in Cameroon for laboratory confirmation. Between March and May 2016, 79 clinically suspected cases were reported including 82.3% (n=65) and 17.7% (n=14) in Oyem and Libreville, respectively. In total, 39.2% (n=31) of children were 11 months-old, 34.2% (n=27) were children aged 1 to 4 years, 11.4% (n=9) were older children from 5 to 9 years, 6.3% (n=5) of children were aged 10 to 15 years and 8.9% (n=7) were 15 years and older. 53.3% (16/30) were laboratory confirmed. This measles outbreak reiterates the importance of maintaining a high level of vaccine coverage in Gabon for vaccine-preventable diseases, as well as the usefulness of a near-real-time surveillance system for the detection of infectious diseases.

Waning of measles maternal antibody in infants in measles elimination settings - A systematic literature review

INTRODUCTION

Most infants are born with immunity to measles through maternal antibodies transferred in pregnancy, which decay over time. However, in measles elimination settings, where measles does not circulate endemically and most immunity is from immunization rather than infection, maternal antibody levels are lower. This results in infant immunity that wanes earlier, and a wider susceptibility gap between maternal antibody decay and infant immunization than in non-eliminated settings. We aimed to systematically quantify the extent and duration of protection from measles in infants in settings that have sustained measles elimination.

METHODS

We conducted a systematic review of studies of measles maternal antibody waning in infants in measles elimination settings. We searched MEDLINE, Embase, CINAHL, Scopus, BIOSIS Previews, and Global Health databases for relevant studies. Studies were included if they were set in countries that had eliminated measles for ≥3 years, and if the study cohort included healthy, full-term, unvaccinated infants ≤12 months, born to healthy mothers, and reported a relevant measure of measles maternal antibody in infants. We assessed study quality using the MetaQAT tool.

RESULTS

We identified 4692 unique citations, eight of which met inclusion criteria. One study reported anti-measles antibody in cord blood, six reported antibody in infant sera, and one reported both. Two studies reported that 80 and 100% of infants were protected from measles at birth. One study reported no protection amongst 3-7 month old infants, and another reported limited protection in infants >4 months. The remaining studies reported the proportion of infants with detected antibody, but not the proportion immune.

CONCLUSION

Although limited, these data suggest that in settings that have sustained measles elimination, some infants are susceptible to measles well before the age of routine measles immunization. Setting-specific seroprevalence and vaccine effectiveness studies are required to evaluate this in different jurisdictions.

Measles elimination and immunisation: national surveillance trends in Japan, 2008-2015

Measles elimination relies on vaccination programmes. In Japan, a major outbreak started in 2007. In response, 5-year two-dose catch-up vaccination programme was initiated in April 2008 for children 13-16-years-old. In this study, we analysed the epidemic curves, incidence rates for each age group, virus genotype, vaccination coverage and ratio of measles gelatin particle agglutination (PA) antibody using surveillance data for 2008-2015. Monthly case counts markedly decreased as vaccination coverage increased. D5, which is the endemic virus type, disappeared after 2011, with the following epidemic caused by imported viruses. Most cases were confirmed to have a no-dose or single-dose vaccination status. Although the incidence rate among all age groups ⩾5-years-old decreased during the study period, for children <5-years-old, the incidence rate remained relatively high and increased in 2014. The ratio of PA antibody (⩾1:128 titres) increased for the majority of age groups, but with a decrease for specific age groups: the 0-5 months and the 2-4, 14, 19 and most of the 26-55- and the 60-year-old groups (-1 to -9%). This seems to be the result of higher vaccination coverage, which would result in decreasing natural immunity booster along with decreasing passive immunity in infants whose mothers did not have the natural immunity booster. The 20-29- and 30-39-year-old age groups had higher number of cases, suggesting that vaccination within these age groups might be important for eliminating imported viruses.

Decreasing Seroprevalence of Measles Antibodies after Vaccination - Possible Gap in Measles Protection in Adults in the Czech Republic

Aims

In recent years, Europe has recorded an increase in the number of measles outbreaks despite the implementation of vaccination into the National Immunization Programs. The Czech Republic introduced vaccination against measles into National Immunization Program in 1969. The aim of this study was to determine seroprevalence of IgG antibodies against measles in adults.

Methods

Our study was designed as a prospective, multicenter cohort study. Samples of blood were taken from adults aged 18 years and over. Specific IgG antibodies were determined by ELISA method.

Results

A number of 1911 sera samples were obtained. The total seropositivity reached 83.3%, 14.3% of the results were negative and 2.4% were borderline. When comparing the individual age groups, the highest antibody seropositivity (> 96%) was detected in persons aged 50 years and over who were naturally infected in pre-vaccine era. The lowest seropositivity was recorded in the age groups 30–39 years (61.5%), 40–49 years (77.5%) and 18–29 years (81.1%).

Conclusions

A long term high rate of seropositivity persists after natural measles infection. By contrast, it decreases over time after vaccination. Similarly, the concentrations of antibodies in persons with measles history persist for a longer time at a higher level than in vaccinated persons. Our results indicate possible gap in measles protection in adults born after implementation of vaccination into the National Immunization Programs. There are two probable reasons, decrease of measles antibody seropositivity in time after vaccination in setting of limited natural booster and one-dose vaccination schedule used in the first years after implementation.

Optimal vaccine schedules to maintain measles elimination with a two-dose routine policy

Measles was eliminated in the Americas in 2002 by a combination of routine immunizations and supplementary immunization activities. Recent outbreaks underscore the importance of reconsidering vaccine policy in order to maintain elimination. We constructed an age-structured dynamical model for the distribution of immunity in a population with routine immunization and without disease, and analysed the steady state for an idealized age structure and for real age structures of countries in the Americas. We compared the level of immunity maintained by current policy in these countries to the level maintainable by an optimal policy. The optimal age target for the first routine dose of measles vaccine depends on the timing and coverage of both doses. Similarly, the optimal age target for the second dose of measles vaccine depends on the timing and coverage of the first dose. The age targets for the first and second doses of measles vaccine should be adjusted for the post-elimination era, by specifically accounting for current context, including realized coverage of both doses, and altered maternal immunity. Doing so can greatly improve the proportion immune within a population, and therefore the chances of maintaining measles elimination, without changing coverage.

The 2013 measles outbreak in Sri Lanka: experience from a rural district and implications for measles elimination goals

BACKGROUND

Sri Lanka was the first country in the Southeast Asian region to achieve its measles elimination goal in 2011. In 2012, the measles immunization schedule changed from a measles vaccine at 9 months to a measles, mumps and rubella vaccine at 12 months. However in 2013, Sri Lanka reported its worst recent outbreak of measles. This study investigated a part of this outbreak in order to describe its epidemiology.

METHODS

A prospective study was carried out at the university medical unit of the Teaching Hospital, Anuradhapura (THA), the third largest hospital in Sri Lanka, from October 2013 until March 2014. An epidemiological profile of patients was constructed, case confirmation was done on all suspected cases and the basic demographic details of these suspected cases were obtained from the available records.

RESULTS

From January 2013 to March 2014, 101 measles suspects were admitted to the THA. Until June 2013, all suspected cases were aged below 12 months of age. During the study period (15 months), the total number of patients aged below 9 months, 9 to 12 months, 1 to 11 years, 12-29 years and over 29 years were 10 (9.9 %), 11 (10.9 %), 6 (5.9 %), 37 (36.6 %) and 36 (35.6 %), respectively (data missing-1). Out of the 33 patients clinically suspected, 32 tested positive for measles. Common clinical features included: fever (n = 33, 100 %), maculopapular rash (n = 33), conjunctivitis (n = 31), posterior cervical lymphadenopathy (n = 23) and Koplik's spots (n = 8). Features suggestive of pneumonia were observed among 30 (90.9 %) patients and 26 (78.8 %) had diarrhoea. Two patients (6.1 %) who developed severe pneumonia received care at an intensive care unit due to respiratory difficulties. Out of 33 patients, 15 (45.5 %) had prior immunization for measles, two (6.1 %) reported that they never had a measles immunization and 16 (48.5 %) were unsure about their immunization status. Out of those who reported they were previously immunized, 11 (73.3 %) belonged to the age group of 12-2 years.

CONCLUSION

Because the first cases of this outbreak were infants, an increase in susceptible infants due to the change in the vaccine schedule could partly explain the outbreak.

Comparative seroprevalence of measles virus immunoglobulin M antibodies in children aged 0-8 months and a control population aged 9-23 months presenting with measles-like symptoms in selected hospitals in Kaduna State

Background

Measles remains the leading cause of vaccine-preventable childhood mortality in developing countries, with its greatest incidence in children younger than 2 years of age. The aim of this study was to determine the seroprevalence of measles virus in children (aged 0–8 months) and older children (aged 9–23 months) presenting with measles-like symptoms.

Methods

A total of 273 blood samples comprising 200 from children aged 0–8 months and 73 from children aged 9–23 months were collected and analyzed for measles virus IgM antibodies by enzyme-linked immunosorbent assay.

Results

An overall prevalence of 21.2% was obtained, with a prevalence of 6.5% in children aged 0–8 months and 61.6% in children aged 9–23 months. The prevalence of measles virus increased with age in children aged 0–8 months and decreased with age in older children (aged 9–23 months), showing a significant association between measles virus and age of the child (P=0.000). A higher prevalence was found in females (27.5%) than in males (16.3%) and this difference was significant (odds ratio 1.942, P=0.025). There was no significant association with the level of parental education, parental occupation, or number of children in the family (P>0.05). With respect to children’s vaccination status and breastfeeding, there was a significant association (P<0.05). The marital status of the family, place of residence, and household size showed no significant association with the prevalence of measles virus. However, a significant association was observed in relation to maternal measles history (odds ratio 2.535, P=0.005) and maternal vaccination status (odds ratio 1.791, P=0.049), as well as between measles virus infection and all presenting symptoms, except for vomiting, malaria, typhoid, and pneumonia, which showed no significant association (P>0.05).

Conclusion

The findings of this study confirm the presence of measles virus infection in children aged 0–8 months.

Prevalence of anti-rubella, anti-measles and anti-mumps IgG antibodies in neonates and pregnant women in Catalonia (Spain) in 2013: susceptibility to measles increased from 2003 to 2013

Non-immune neonates and non-immune pregnant women are at risk of developing rubella, measles and mumps infections, including congenital rubella syndrome. We describe the seroepidemiology of measles, mumps and rubella (MMR) in neonates and pregnant women in Catalonia (Spain). Anti-rubella, anti-measles and anti-mumps serum IgG titres were assessed using enzyme-linked immunosorbent assay (ELISA) tests in 353 cord blood samples from neonates of a representative sample of pregnant women obtained in 2013. The prevalence of protective antibody titres in neonates was 96 % for rubella IgG (≥8 IU/ml), 90 % for measles IgG (>300 IU/ml) and 84 % for mumps IgG (>460 EU/ml). Slightly lower prevalences of protective IgG titres, as estimated from the cord blood titres, were found in pregnant women: 95 % for rubella IgG, 89 % for measles IgG and 81 % for mumps IgG. The anti-measles and anti-mumps IgG titres and the prevalences of protective IgG titres against measles and mumps increased significantly (p < 0.001) with maternal age. The prevalence of protective anti-measles IgG titres decreased by 7 % [odds ratio (OR) = 0.15, p < 0.001), the prevalence of protective anti-rubella IgG titres increased by 3 % (OR = 1.80, p < 0.05) and the MMR vaccination coverage (during childhood) in pregnant women increased by 54 % (OR = 2.09, p < 0.001) from 2003 to 2013. We recommend to develop an MMR prevention programme in women of childbearing age based on mass MMR vaccination or MMR screening and vaccination of susceptible women to increase immunity levels against MMR.

[Hot spot: epidemiology of measles and rubella in Germany and the WHO European region]

The elimination of measles and rubella by 2015 is an important goal set by the World Health Organization European Region (WHO/Europa). Since 1991, the incidence of measles in WHO/Europa declined owing to routine childhood vaccination and supplementary immunization activities in the region. However, in many countries of Western Europe elimination of measles and rubella remains a challenge, and every year there are outbreaks with partly long-lasting transmission chains and dissemination of the virus internationally. In Germany, outbreaks occur because of the high proportion of susceptible individuals in specific population groups. In 2011, over 1,600 cases were reported (19.7 per 1,000,000 inhabitants, data from the Robert Koch Institute) whereas in 2012 only 167 cases were reported to the Robert Koch Institute (2 per 1,000,000 inhabitants). It is unclear whether the declining trend will continue in the following years due to improved vaccination coverage or whether number of cases will rise again because of the accumulation of susceptible groups. In Germany, there are currently no representative, country-wide data on rubella; however, data from the eastern federal states provide important epidemiological insights. Outbreaks are seldom reported, but statutory notification of rubella and congenital rubella syndrome was implemented in March 2013. As a result, it will be possible to better assess the epidemiology of rubella in Germany, although a considerable underreporting of rubella cases is anticipated.

Duration of maternally derived antibody against measles: a seroepidemiological study of infants aged under 8 months in Qinghai, China

To estimate the sero-prevalence of protective maternal measles antibodies among young infants and examine patterns of waning immunity in one of the poorest provinces in China, infants aged under 8 months and their mothers were randomly selected by multi-stage probabilistic sampling and blood samples were collected. Measles-specific IgG antibodies were measured in all serum samples by enzyme-linked immunosorbent assay. We determined measles-specific antibody titres for 477 pairs of infants and their mothers. After excluding 44 sub-clinical measles infection in infants, the measles antibody titres were ≧1:200, ≧1:800, and ≧1:3200 in 79.2%, 46.9%, and 17.8% of the 433 infants, respectively. The proportion of infants with titre ≧1:800 declined with age from 90.2% in newborns to 45.5% and 14.9% in the fourth and eighth month, respectively. Among the 433 mothers, measles antibody titres were ≧1:800 in 94.0%. Multivariate regression analysis showed that residence, mother's antibody levels and infant's age were significantly associated with infants' having a measles antibody titre ≧1:800. The relatively rapid decay of protective antibody in infants suggests that an earlier administration of the first dose of measles vaccination should be considered in China and a high quality interventional study is needed to decide the optimal schedule of measles immunization.

Kinetics of decline of maternal measles virus-neutralizing antibodies in sera of infants in France in 2006

The optimal age for measles vaccination is an important health issue, since maternal antibodies may neutralize the vaccine antigen before a specific immune response develops, while delaying vaccination may increase the risk of complicated diseases in infants. However, measles vaccination impacts the duration of protection afforded by transplacental transfer of maternal antibodies: vaccination-induced maternal antibodies disappear faster than disease-induced antibodies. In order to maintain protection against measles in infants, it is important to monitor the dynamics of this phenomenon in vaccinated populations. To assess the current situation in France, a multicenter, prospective seroepidemiological study was conducted in seven French hospitals between October 2005 and January 2007. Maternal measles antibody concentrations from 348 infants 0 to 15 months old were measured using the plaque reduction neutralization assay. Geometric mean concentrations and the percentage of infants with maternal measles antibody concentrations above the protection threshold (>or=120 mIU/ml) were assessed according to age. Results show that after more than 20 years of routine measles vaccination in France, maternal measles-neutralizing antibodies decrease dramatically in French infants by 6 months of age, from 1,740 mIU/ml for infants 0 to 1 month old to 223 mIU/ml for infants 5 to 6 months old, and that 90% of infants are not protected against measles after 6 months of age. Infant protection against measles could be optimized both by increasing herd immunity through an increased vaccine coverage and by lowering the age of routine vaccination from 12 to 9 months.

Passive transmission and persistence of naturally acquired or vaccine-induced maternal antibodies against measles in newborns

This paper reviews literature on passively transferred maternal antibodies against measles in infants. The amount and decay of these antibodies can be a result of changing patterns in society: increasing cohorts of women are vaccinated against measles instead of having naturally acquired immunity, the age of first childbirth is increasing and young adults are less exposed to natural boosters. The concentration and persistence of maternal antibodies differ in infants of women vaccinated against measles versus infants of naturally immune women. The date for commencing universal measles vaccination should take into account the presence of these antibodies since they can hamper the immunological response to vaccination. Each country should therefore consider adapting the timing of vaccination in relation to its measles sero-epidemiological situation. The possibility of priming the immune system with an early vaccine dose and boosting later on offers opportunities for vaccination at very young age.

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.

Levels of rubella antibody among vaccinated and unvaccinated Portuguese mothers and their newborns

Maternal and cord sera (231 pairs) were tested to measure rubella IgG levels, using a commercial immunoassay method with final fluorescent detection (ELFA). One hundred and twenty-two women had been vaccinated against rubella. Geometric mean concentrations (GMC) were not associated with time since vaccination. GMC of rubella IgG among vaccinated and unvaccinated mothers were respectively 66.6 and 80.9IU/ml (p=0.29). The corresponding values for cord sera GMC were 140.6 and 140.2IU/ml (p=0.99). These GMC values seem to have been influenced by increased transplacental transport efficiency (TTE) among vaccinated mothers. This was observed if TTE was measured as difference or ratio of cord-maternal concentration of rubella IgG, but was only statistically significantly (p=0.02) for ratio. TTE also seemed to be higher when antibody levels in mothers were below <15IU/ml. There seemed to be some interaction between susceptibility and vaccination status, but these results should be seen with caution. We do not know of a proven biological reason to support differential TTE in vaccinated and unvaccinated mothers. The sensitivity of the lab assay might have influenced the results, such that very low antibody levels in some vaccinated mothers were underestimates of true concentrations. Our finding that 38 mothers had antibody levels considered to be below the threshold for protection highlights the importance of implementing policies to vaccinate susceptible women of childbearing age.

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.

Placental transfer of measles antibodies: effect of gestational age and maternal vaccination status

Despite nationwide measles vaccination coverage in Israel of over 90%, repeated outbreaks of measles have spread from isolated communities with poor immunization uptake. Some severely affected individuals were children under 1 year of age, including premature infants. We evaluated the serological status of 195 newborn infants and their 161 mothers divided into four groups: vaccinated mothers (VMs) and premature infants, VM and full term infants, naturally immunized mothers (NIMs) and premature infants, NIM and full term infants. Maternal and cord blood measles antibody titers were determined by haemagglutination inhibition (HI) test and microneutralization test (mNT). Fewer than 40% of preterm infants of VM and less then 70% of preterm infants of NIM had protective titers at birth. The results of this study may aid in formulating new measles vaccination recommendations for preterm infants.

Measles outbreak in Sri Lanka, 1999-2000

A large measles outbreak occurred in Sri Lanka from October 1999 through June 2000 following a period of low incidence. During this period, >15,000 suspected cases were reported to the central Epidemiological Unit of the Department of Health Services. The outbreak was investigated through review of surveillance data for 1999-2000, which were compared with previous surveillance data. Among the clinically confirmed cases, the highest morbidity rate (114/100,000 population) was observed among children <9 months of age. Nearly 54% of the cases were among persons >/=15 years old, and this percentage had increased over the previous decade. Forty percent of cases had a history of measles vaccination. There were 5 deaths, giving a case-fatality rate of 0.1%. Action taken during the outbreak and plans for future outbreak prevention strategies were also evaluated.

Experimental vaccines against measles in a world of changing epidemiology

Vaccination with the current live attenuated measles vaccine is one of the most successful and cost-effective medical interventions. However, as a result of persisting maternal antibodies and immaturity of the infant immune system, this vaccine is poorly immunogenic in children <9 months old. Immunity against the live vaccine is less robust than natural immunity and protection less durable. There may also be some concern about (vaccine) virus spread during the final stage of an eventual measles eradication program. Opinions may differ with respect to the potential threat that some of these concerns may be to the World Health Organisation goal of measles elimination, but there is a consensus that the development of new measles vaccines cannot wait. Candidate vaccines are based on viral or bacterial vectors expressing recombinant viral proteins, naked DNA, immune stimulating complexes or synthetic peptides mimicking neutralising epitopes. While some of these candidate vaccines have proven their efficacy in monkey studies, aerosol formulated live attenuated measles vaccine are evaluated in clinical trials.

Comparison of immunogenicity and reactogenicity of a measles, mumps and rubella (MMR) vaccine in German children vaccinated at 9-11, 12-14 or 15-17 months of age

Children aged 9-11, 12-14 or 15-17 months, respectively were vaccinated with a measles, mumps and rubella (MMR) vaccine and serum antibody responses and reactogenicity were compared. The data of 118 children could be analysed (group 1=9-11 months, n=46; group 2=12-14 months, n=29, group 3, 15-17 months, n=43). The only significant difference observed was for seroconversion against measles virus between group 1 and group 3 (84.8% vs 100%, p=0.012). No serious adverse events were reported. Local side reactions were mild, infrequent and independent of age. Immunisation against MMR is safe and effective even when administered before the currently recommended age of 12 months.

Factors determining prevalence of maternal antibody to measles virus throughout infancy: a review

The effectiveness of vaccination against measles, the leading cause of vaccine-preventable deaths in infants globally, is greatly impacted by the level of maternal antibody to measles virus (or "measles maternal antibody"; MMA) during infancy. Variation in the prevalence of maternal antibody to measles virus between infant populations across countries and sociodemographic strata is poorly understood. We reviewed the literature on the prevalence of MMA, focusing on 3 principal determinants: starting level of maternal antibody, placental transfer of maternal antibody, and rate of decay of maternal antibody after birth. Our review identified placental transfer as an important determinant, with greater efficiency found in studies performed in developed countries. Placental transfer was influenced by gestational age, human immunodeficiency virus infection, and malaria. Antibody levels in mothers varied widely between countries, although predictably according to vaccination status within populations. Rates of antibody decay across studies were similar. Future studies should evaluate the utility of the cord blood level of MMA as a predictor of vaccine efficacy in infancy; inclusion of World Health Organization international reference sera will facilitate comparisons. Greater understanding of the determinants of the prevalence of MMA will help national policy makers determine the appropriate age for measles vaccination.

Sero-epidemiology of measles antibodies in the Netherlands, a cross-sectional study in a national sample and in communities with low vaccine coverage

Serum antibodies against measles were measured in the Dutch general population and in municipalities with low vaccine coverage, where religious groups that refuse vaccination are clustered sociogeographically. The results suggest that wild measles virus may still circulate in municipalities with low vaccine coverage; the circulation in the general population seems to have decreased significantly right after the introduction of mass vaccination. The overall prevalence in the general population was high (95.7%, 95% confidence limits 95.3-96.2%); the seroprevalence in the age groups offered two vaccinations (91.7%, 95% confidence limits 89.4-94.0%) was lower than the level believed to be necessary for the elimination of measles. Protective levels of maternal antibodies in newborns have waned several months before the first vaccination is scheduled.

Detection of measles specific IgG in oral fluid using an FITC/anti-FITC IgG capture enzyme linked immunosorbent assay (GACELISA)

An IgG antibody capture enzyme linked immunosorbent assay (GACELISA) for the detection of measles specific IgG in oral fluid was developed using an FITC/anti-FITC amplification system. The GACELISA was evaluated by testing paired oral fluid and serum samples from 787 subjects in an epidemiological study of measles in rural Ethiopia. Oral fluids were tested by GACELISA and corresponding serum samples by a sensitive indirect ELISA for measles IgG (Behring Enzygnost). By comparison with the serum measles IgG assay, the oral fluid GACELISA had a sensitivity of 97.4% (95% confidence intervals: 95.9, 98.2) and a specificity of 90.0% (81.9, 94.3), with no significant differences observed by age group. Total IgG concentrations were measured on a subset of 160 oral fluids by an in-house ELISA. This showed that false negative GACELISA results tended to occur in samples with low concentrations of total IgG, although the trend was not statistically significant. It is concluded that the overall performance of the GACELISA was satisfactory, showing close agreement to the serum ELISA, and has potential to serve as an easily transferable tool for large scale epidemiological studies as required for the World Health Organisation's programme for the global control of measles.

Decay of passively acquired maternal antibodies against measles, mumps, and rubella viruses

The decay of maternally derived antibodies to measles, mumps, and rubella viruses in Swiss infants was studied in order to determine the optimal time for vaccination. A total of 500 serum or plasma samples from infants up to 2 years of age were tested by enzyme-linked immunosorbent assay and fluorescent-antibody testing. The decline of antibody prevalence was slowest against the measles virus. By 9 to 12 months of age, only 5 of 58 (8.6%; 95% CI, 2.9 to 19.0) infants were antibody positive for the measles virus, and only 2 had levels above 200 mIU/ml. Mumps and rubella virus antibody seropositivity was lowest at 9 to 12 months of age with 3 of 58 (5. 2%; 95% CI, 1.1 to 14.4) infants and at 12 to 15 months with 1 of 48 (2.1%; 95% CI, 0.1 to 11.1) infants, respectively. Concentrations of passively acquired antibodies decreased rapidly within the first 6 months of life. We observed no significant differences in antibody prevalence or concentration according to gender in any age group. In conclusion, MMR vaccination at 12 instead of 15 months of age could reduce the pool of susceptible subjects in infancy and support the efforts to eliminate these infections, particularly in combination with a second vaccine dose before school entry.

Comparison of a commercial enzyme immunoassay with plaque reduction neutralization for maternal and infant measles antibody measurement

The most practicable assay for measurement of measles IgG (mIgG) in large numbers of sera is an enzyme immunoassay (EIA). To assess how EIA results would agree with those by the gold standard method of plaque reduction neutralization (PRN) we compared the results from the two methods in 43 pairs of maternal and umbilical cord sera, and sera from the corresponding infants when aged 11-14 months. In maternal-cord sera, the differences between mean antibody levels by EIA or PRN were not statistically significant, though in individual sera, differences could be large. However, agreement was less good for infants sera, in which levels of mIgG were very low. The conclusions of a study of transplacental transport of mIgG would not be affected by the use of either technique. When studying waning immunity in infants, PRN should be the method of choice, while results from studies using EIA should be interpreted with caution.

Genetic and antigenic characterisation of the haemagglutinin protein of measles virus strains recently circulating in the UK

The complete nucleotide sequence of the H protein gene of seven measles virus (MV) strains, representing three MV genotypes circulating in the UK in recent years, was determined. Compared to the MV vaccine strain Moraten (Mor-v), the divergence of the coded H gene (aal-600) of the seven UK strains was between 1.8% and 2.8%. Representative isolates from each of the genotypes were tested by radio-immunoprecipitation using a panel of H protein-specific MAbs. Different patterns of MAb reactivity were shown between the three genotypes and between the wild-type strains and the vaccine strain. Plaque reduction neutralising antibody titres against strains UK350/94 (genotype I) and UK226/94 (genotype III) were measured in sera from 11 vaccinees. Vaccine derived antibody neutralised both strains and the GMTs were not significantly lower against the wild-type strains than against strain Mor-v.