Measles Antibodies in Mother-Infant Dyads in Tianjin, China

Measles seroprevalence in Thailand: are adolescents and young adults at risk of measles?

INTRODUCTION

During the last decade, measles has become an important re-emerging disease in Thailand. The objective of this study was to measure measles seroprevalence and its influencing factors so as to plan an improved vaccination programme.

METHODS

A total of 600 participants aged between 9 months and 50 years were divided into seven groups representing birth cohorts that experienced different measles vaccination policies. Participants' blood samples were obtained to measure measles immunoglobulin G (IgG) levels.

RESULTS

None of the participants in the age group of 9 months had measles IgG levels beyond a protective level. Participants in the age groups 2.5, 5-15, 16-29, 30-33, 34-40 and 41-50 years had 82% (95% confidence interval [CI] 73.3-90.7), 50% (95% CI 36.1-63.9), 52% (95% CI 42.3-62.7), 70% (95% CI 61.1-78.9), 88.8% (95% CI 84.1-93.5) and 98.8% (95% CI 96.4-100.0) measles seropositivity, respectively. The study did not find any significant factors affecting measles seropositivity.

CONCLUSION

Individuals aged 15-34 years are vulnerable to measles infections. Supplementary vaccination should be encouraged in special situations, including postexposure prophylaxis for young adults during an outbreak and for high-risk occupations such as healthcare personnel.

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.

Maternally transmitted anti-measles antibodies, and susceptibility to disease among infants in Chandigarh, India: A prospective birth cohort study

Prior to the age of measles vaccination, infants are believed to be protected against measles by passively transferred maternal antibodies. However, the quantity and quality of such protection have not been well established in the Indian setting. We undertook this study to characterize the transfer and decline in maternal anti-measles antibodies among infants, and determine their susceptibility to measles. In this population-based, birth-cohort study, we enrolled pregnant women and their newborn infants, from a catchment area of 30 Anganwadis in Chandigarh, India. We collected maternal blood at delivery, and infant blood samples at birth, and 3, 6, and 9 months of age. Anti-measles IgG antibodies were measured using quantitative ELISA. We assessed antibody decline using log-linear models. In total, 428 mother-infant dyads were enrolled, and data from 413 dyads were analyzed. At birth, 91.5% (95% CI: 88.8, 94.2) of infants had protective antibody levels, which declined to 26.3% (95% CI: 21.0%, 31.9) at 3 months, 3.4% (95% CI: 0.9, 5.9) at 6 months, and 2.1% (95% CI: 0.1, 4.1) at 9 months. Younger mothers transferred lower levels of antibodies to their infants. We concluded that the majority of infants are susceptible to measles as early as three months of age, much earlier than their eligibility to receive measles vaccination.

Waning of maternal antibody against measles virus in Shufu, China

BACKGROUND

As measles vaccination coverage has increased, measles infection has shifted to the population of infants. We conducted a follow-up seroepidemiological study among mothers and their infants to evaluate measles seroprevalence and the persistence of maternal measles antibody in Shufu, Kashgar from 2018 to 2020.

METHODS

Maternal venous blood and cord blood was obtained among mothers and their infants at 0, 3, 5, 8, 9, and 12 months of age. An enzyme-linked immunosorbent assay was used for quantitative measurement of measles antibodies. We analyzed the correlation between maternal and neonatal measles antibodies, and antibodies persistence after infants were born.

RESULTS

The overall neonatal maternal ratio was 2.38 (95%CI: 2.05-2.71). The measles antibodies for mothers and newborns were 438.93 IU/mL (95%CI: 409.47-470.51 IU/mL) and 440.10 IU/mL (95%CI: 410.82-471.48 IU/mL), respectively. Neonatal measles antibodies were dropping after birth and then beginning to increase starting at 8 months of age.

CONCLUSIONS

Infant measles antibody levels progressively declined after birth regardless of maternal measles antibody levels. Efforts should be carried out to eliminate measles.

One single-center serological survey on measles, rubella and mumps antibody levels of people in Youyang, China

Although measles, rubella and mumps elimination had achieved great progress in recent years, outbreaks were still reported worldwide. Serological surveillance on the remaining susceptibility in the population is essential to evaluate the preventive policy, estimate the current risk of infection, and predict evolutions in the future. In this study, we aimed to investigate the prevalence of seropositivity of antibodies against measles, rubella and mumps in a population of all ages in Youyang, southwest China. A cross-sectional hospital-based study was conducted among 657 cases who attended to Youyang Hospital from Sep 2018 to Aug 2019. Sero IgG antibodies were measured by ELISA. No difference in the seropositivity of antibodies against measles, rubella and mumps was found between neither urban vs. rural, nor male vs. female. The overall seropositivity of anti-measles, rubella, mumps IgG antibodies was 81.1% (95% CI: 78.0-83.9), 65.9% (95% CI: 62.2-69.4) and 63.2% (95% CI: 59.4-66.8), respectively. The IgG seropositivity varied with age significantly. In this study, the seropositivity of antibodies against measles, rubella and mumps among the participants was insufficient in the population, especially among infants, teenagers and productive women, who were suggested to booster the immunity. To better control and eliminate measles, mumps and rubella-related diseases, nation-wide active laboratory-supported surveillance, outbreak investigation and revaccination for vulnerable population are needed.

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.

Measles vaccination of young infants in China: A cost-effectiveness analysis

BACKGROUND

Although global progress in measles control has been realized, achieving elimination has proven difficult in many regions of the world. China has adopted a goal of measles elimination but recent outbreaks predominantly affecting children <8 months who are ineligible for vaccination and incompletely protected by maternal antibodies has impeded progress. We assess the cost-effectiveness of adding an initial measles vaccine dose in China to earlier than the currently recommended 8 months of age.

METHODS

We conducted a cost-utility analysis comparing the costs and health benefits associated with adding a measles vaccine dose to the routine schedule at 4, 5, 6 or 7 months compared to the current recommendation for the first dose at age 8 months. A decision analytic model was developed in Microsoft Excel, including five non-severe and two fatal health outcomes associated with measles infection. Model parameters were informed by the literature and surveillance data. Future costs and health benefits were discounted at 3%. Primary outcomes included costs, Quality-adjusted life years (QALYs), and incremental cost-effectiveness ratio (ICER) over a lifetime time horizon.

RESULTS

Lowering the recommended age for initiating the measles vaccination series to address susceptibility in children <8 months provided incremental health gains compared to minimal costs at the individual-level. The ICER was most favorable ($232.70 per QALY gain) for administering an initial dose at 4 months of age due to fewer incremental program costs when shifting measles administration to an immunization visit already established under the Chinese vaccination program.

CONCLUSION

We found potential beneficial health gains at a minimum cost associated with adding an earlier measles dose <8 months of age in China. Further investigation about disease transmission dynamics is required to more fully assess the tradeoffs of administering measles at a younger age to infants in China.

Measles Antibody Levels in Young Infants

BACKGROUND

Infants are often assumed to be immune to measles through maternal antibodies transferred during pregnancy and, in many countries, receive their first measles-containing vaccine at 12 to 15 months. Immunity may wane before this time in measles-eliminated settings, placing infants at risk for measles and complications. We investigated humoral immunity to measles in infants <12 months of age in Ontario, Canada.

METHODS

We selected sera collected at a tertiary pediatric hospital from infants <12 months who were born at ≥37 weeks' gestational age. We excluded infants with conditions that affect antibody levels. We selected ≤25 sera from 8 predetermined age bands and tested them for measles-neutralizing antibody using the plaque-reduction neutralization test. We calculated the proportion immune at each age band, and predictors of infant susceptibility were assessed by using multivariable logistic regression and Poisson regression.

RESULTS

Of 196 infant sera, 56% (110 of 196) were from boys, and 35% (69 of 196) were from infants with underlying medical conditions. In the first month, 20% (5 of 25) of infants had antibodies below the protective threshold, which increased to 92% (22 of 24) by 3 months. By 6 months, all infants had titers below the protective threshold. In a multivariable analysis, infant age was the strongest predictor of susceptibility (odds ratio = 2.13 for each additional month increase; 95% confidence interval: 1.52-2.97).

CONCLUSIONS

Most infants were susceptible to measles by 3 months of age in this elimination setting. Our findings inform important policy discussions relating to the timing of the first dose of measles-containing vaccine and infant postexposure prophylaxis recommendations.

Early Waning of Maternal Measles Antibodies in Infants in Zhejiang Province, China: A Comparison of Two Cross-Sectional Serosurveys

In China, children aged <8 months, who were expected to be protected by maternal antibodies before receiving the first dose of measles vaccine, were the age group with the greatest risk of infection in recent years. In this study, we evaluated whether infants yet to be age-eligible for measles vaccine had a sufficient seropositive level of maternal measles antibodies in 2009 and 2013. Blood samples were collected from infants aged <8 months through population-based serological surveys conducted in Zhejiang, China. Serum levels of immunoglobulin G measles antibodies were quantified using enzyme-linked immunosorbent assay. In 2013, the mean geometric mean titres (GMTs) of infants aged 4 to 8 months were below the seropositivity threshold (<200 mIU/mL), decreasing from 118.6 mIU/mL (95% confidence interval [CI] 83.0, 169.3 mIU/mL) at 4 months to 28.6 mIU/mL (95% CI 15.6, 52.3 mIU/mL) at 7 months. Antibody levels were significantly lower in 2013 than in 2009 starting from 5 months of age. In conclusion, infants aged 4 to 8 months are susceptible to measles due to low levels of maternal measles antibodies. It is thus suggested to provide infants with a supplementary dose on top of the routine schedule, and/or launch catch-up vaccination campaigns among young women.

Measles and Rubella Seroprevalence in Mother-Infant Pairs in Rural Nepal and the United States: Pre- and Post-Elimination Populations

We sought to compare seroprevalence of protective measles and rubella-specific antibody in mother-infant pairs across two populations: a pre-disease elimination Nepal population with recently introduced rubella vaccine and post-disease elimination U.S. population. Qualitative measles and rubella immunoglobulin G was assessed in maternal serum and cord blood from 258 pairs in Nepal, 2012-2013 and 49 pairs in Seattle, WA, 2014-2015. High rates of protective antibody were observed in both populations. Two hundred and forty-four (95%) pregnant women in Nepal had protective measles antibody versus 44 (92%) in Seattle (P = 0.42). Ninety-six percent of infants in Nepal (N = 246) and Seattle (N = 43) had protective measles antibody (P = 0.75). Ninety-four percentage of pregnant women in Nepal (N = 242) and Seattle (N = 45) had protective rubella antibody (P = 0.23). Two hundred and thirty-eight (93%) infants in Nepal had protective rubella antibody versus 44 (98%) in Seattle (P = 0.12). Continued surveillance will be necessary to ensure protective immunity, inform progress toward disease elimination in Nepal and avoid reemergence in the United States.

Monitoring the age-specificity of measles transmissions during 2009-2016 in Southern China

Background

Despite several immunization efforts, China saw a resurgence of measles in 2012. Monitoring of transmissions of individuals from different age groups could offer information that would be valuable for planning adequate disease control strategies. We compared the age-specific effective reproductive numbers (R) of measles during 2009–2016 in Guangdong, China.

Methods

We estimated the age-specific R values for 7 age groups: 0–8 months, 9–18 months, 19 months to 6 years, 7–15 years, 16–25 years, 26–45 years, and ≥46 years adapting the contact matrix of China. The daily numbers of laboratory and clinically confirmed cases reported to the Center for Disease Control and Prevention of Guangdong were used.

Results

The peak R values of the entire population were above unity from 2012 to 2016, indicating the persistence of measles in the population. In general, children aged 0–6 years and adults aged 26–45 years had larger values of R when comparing with other age groups after 2012. While the peaks of R values for children aged 0–6 years dropped steadily after 2013, the peaks of R values for adults aged 26–45 years kept at a high range every year.

Conclusions

Although the provincial supplementary immunization activities (SIAs) conducted in 2009 and 2010 were able to reduce the transmissions from 2009 to 2011, larger values of R for children aged 0–6 years were observed after 2012, indicating that the benefits of the SIAs were short-lived. In addition, the transmissions from adults aged between 26 and 45 years increased over time. Disease control strategies should target children and adult groups that carry high potential for measles transmission.