Measles virus specific antibody in infants in a highly vaccinated society

Live attenuated vaccine efficacy six months after intravenous immunoglobulin therapy for Kawasaki disease

BACKGROUND

Due to the presence of maternal passive antibodies, the measles vaccine is ineffective if administered before age 12-15 months. The optimal timing for administering a live attenuated vaccine (LAV) after intravenous immunoglobulin therapy (IVIG) for Kawasaki disease (KD) has not been fully investigated. The recommended interval between vaccination and IVIG therapy for KD differs by country. The present study aimed to evaluate efficacy of LAV six months after IVIG therapy for KD in Japan.

METHODS

The present, single-arm, prospective, interventional study included patients aged 6 months or older with no medical history of measles, rubella, varicella or mumps or vaccinations against these diseases. The subjects received these vaccinations for the first time at six months after IVIG therapy. Virus-specific IgG levels for each virus measured by EIA was examined at nine months after IVIG therapy. If the results were negative, the subjects received a booster vaccination at 12 months after IVIG therapy. The primary outcome was the prevalence of positivity for antibodies after the initial and booster vaccinations.

RESULTS

The present study enrolled 32 subjects, 31% of whom were female, with an average age of 10.8 (standard deviation 2.8) months at IVIG therapy. At six months after IVIG therapy, 9% and 6% of the subjects were seropositive for measles and varicella titers, respectively, but were seronegative for the mumps and rubella titers. The seroconversion rate for measles, mumps, rubella, and varicella after the initial vaccination was 88%, 6%, 78%, and 16%, respectively. The seroconversion rate after a booster vaccination was 100% for measles and rubella, 97% for mumps, and 77% for varicella.

CONCLUSIONS

The seroconversion rate was low for LAV at six months after a single dose of IVIG for KD, but seroconversion was achievable with a booster vaccination at 12 months.

CLINICAL TRIAL REGISTRATION

UMIN-CTR, UMIN000007174, https://upload.umin.ac.jp/cgi-open-bin/ctr/ctr_view.cgi?recptno=R000008452.

Pre-vaccination evolution of antibodies among infants 0, 3 and 6months of age: A longitudinal analysis of measles, enterovirus 71 and coxsackievirus 16

BACKGROUND

Due to waning levels of maternal antibodies (measles; enterovirus 71, EV71; and coxsackievirus A16, CoxA16), some infants may lose protection against infection prior to vaccination. Using a longitudinal design, we examine how maternal antibody levels evolve over time in infants prior to vaccination.

METHODS

In 2013-2014, we collected sera at ages 0, 3 and 6months from infants. We assayed for levels of measles IgG antibody (717, 233 and 75 sample sera tested at months 0, 3 and 6, respectively), and neutralizing antibodies for EV71 and CoxA16 (225, 217, and 72). Demographic and health information were collected, and a linear mixed model (LMM) was used to describe antibody levels over time.

RESULTS

Pre-vaccination monotonic antibody decreases were observed for measles (1410, 195 and 22mIU/ml, p<0.001), EV71 (1:19.9, 6.3 and 4.5, p<0.001) and CoxA16 (1:16.3, 5.9, and 4.5, p<0.001). At 6months of age, only 2.7% (95%CI, 0.6-8.3), 6.8% (95%CI, 2.7-14.4) and 5.6% (95%CI, 1.9-12.7) of infants were antibody positive for measles, EV71 and CoxA16, respectively. LMM findings indicated that infants with higher antibody titers at birth experienced a greater loss of antibody level. An infection rate of 1.3% (95%CI, 0.1-6.1) was reported for both EV71 and CoxA16.

CONCLUSIONS

Further modifications of vaccination strategies for measles, earlier vaccination for EV71 infection, and deployment of a CoxA16 vaccine need to be considered to limit infection among the very young.

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.

Immunity against measles in populations of women and infants in Poland

During the 1997-1998 measles epidemic in Poland a high attack rate occurred in infants up to 1 year of age (24.6/100,000 in comparison with 5.5/100,000 in total population). Routine vaccination against measles for infants aged 13-15 months was introduced in Poland in 1975, and a second dose added in 1991. The recommended age for measles vaccination was based on information gathered in years when most mothers had a natural measles. Nowadays, many mothers have received measles vaccine. Early loss of passively acquired measles antibody may occur in infants of women who received measles vaccine, because measles vaccine induces lower antibody titres than does natural infection. Therefore, measles-specific antibody titres were determined among vaccinated and unvaccinated women as well as among infants, whose mothers were born after 1976 and likely were vaccinated (Group 1), and those, whose mothers were born before 1969 and likely have had a natural measles (Group 2). All women that were born in prevaccination era had significantly higher geometric mean titre (GMT) of measles antibody than those who were vaccinated (P<0.001). Also infants from Group 2 at every age had higher GMT of measles antibody than those of Group 1. The antibody decay was significantly faster among infants whose mothers acquired immunity by measles vaccination. Because nowadays the majority of women in childbearing age are vaccinated against measles, earlier vaccination in the infants should be considered.

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.

Immune response to measles vaccine in 6-month-old infants of measles seronegative mothers

Determinants of measles vaccine-induced immune response in infancy include maternal immune status and the infant's age at immunization. In a previously published study, 74% of 19 6-month-old infants developed neutralizing antibody. Two of the infants were born to measles seronegative mothers. In order to (1) assess the prevalence of measles seronegativity in a population of US mothers born after 1960 and (2) assess the immunogenicity of standard titer measles vaccine in 6-month-old infants of measles seronegative mothers, mothers with healthy term (> or = 37 weeks gestation) infants attending well child care clinics at MetroHealth Medical Center were prospectively screened for measles antibody by EIA. If negative, maternal samples were retested for neutralization (NT) antibody. Fifteen of 169 women were seronegative by both assays. Six-month-old infants of 9 of these 15 seronegative mothers were enrolled in the pediatric vaccine study. Serological response of these 9 infants to monovalent measles vaccine (Attenuvax) was compared to the responses of 17 6-month-old infants of seropositive mothers and 15 15-month-old toddlers from our previous study. All 9 infants of seronegative mothers became EIA seropositive after the vaccine compared to 9 of 17 6-month-old infants born to seropositive mothers (p = 0.02). Differences in NT seroconversion rates (100% vs 70.6%) were not statistically significant. The comparison group of 15-month-old vaccinees showed 100% seroconversion by both assays. The NT geometric mean titer (GMT) was higher in the 15-month-old toddlers than in the 6-month-old infants born to seronegative mothers (87.2 vs 33.9, p < 0.01), suggesting age-related differences in humoral immune response unrelated to passively transferred maternal antibody.

Orally administered microencapsulated reovirus can bypass suckled, neutralizing maternal antibody that inhibits active immunization of neonates

Purified reovirus serotype 1, encapsulated in biodegradable aqueous microcapsules, was found to bypass maternal antibody passively transferred by suckling to neonates. Genetically identical, immunocompetent F1 scid/+ mice were generated by the reciprocal crosses of C.B17 scid/scid and normal congenic +/+ adult mice. The immunocompetent +/+ dams were either orally infected with reovirus prior to mating or not. Thus, these immunocompetent F1 pups developed either in the absence or in presence of passively transferred maternal immunity. The F1 mice were orally immunized on day 10 with either live virus, microencapsulated reovirus, or empty microcapsules plus live virus. The immune responses were assessed in the neonatal gut-associated lymphoid tissues (GALT). Examination of reovirus specific immunoglobulin A in the serum and GALT, taken on days 7, 14, and 21 postimmunization, clearly demonstrated that microencapsulated reovirus could bypass the normal effect of maternal antibodies, passively acquired by suckling, to inhibit active priming of neonates by oral route. These observations seem relevant to the development of efficacious oral vaccines that also allow passive, protective immunity via suckled maternal antibodies while permitting active oral immunization of neonates.

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

Maternal, cord and infant measles antibody levels were measured and compared in a group of 411 vaccinated mothers and 240 unvaccinated mothers, and their babies, between 1983 and 1991. Maternal and cord sera were tested by haemagglutination inhibition and/or enzyme-linked immunosorbent assay, and plaque reduction neutralization tests were also used to test infant sera. Geometric mean titres were significantly higher in the unvaccinated than in the vaccinated mothers (P < 0.001). Infants born to mothers with a history of measles had higher antibody levels at birth than infants of vaccinated mothers and, although the difference narrowed over time, continued to have higher levels up to 30 weeks of age. Between 5 and 7 months of age significantly more of the children of vaccinated mothers had plaque reduction neutralization antibody levels below that which would interfere with vaccination. As the boosting effect of circulating natural measles disappears, earlier measles vaccination may need to be considered, perhaps as part of a two-dose policy.

Antibody response to measles vaccination in Turkish children

In recent years, there has been a remarkable increase in measles cases among preschool and secondary school children in Turkey, as in many other countries. The seroconversion and coverage rates of measles vaccine should therefore be evaluated in order to obtain data that could be used to determine the vaccination policy for Turkey. Measles immunity status was studied by an enzyme-linked immunosorbent (ELISA) test determining the anti-measles IgG antibody levels. Measles specific IgG antibodies were found to be positive in 77.88% of the entire study group of 800 children aged 11 months to 12 years, while 21.25% had negative sera. Seven (0.87%) subjects had borderline results. The results of this study indicate the need to administer a second dose of measles vaccine, preferably at 18 months of age concomitant with other vaccines. This vaccination policy, together with an increase in the extent of immunization coverage, may help to achieve the World Health Organization's (WHO) target of the complete eradication of measles.

Measles vaccination policy

Where immunization campaigns locally eliminate measles, it will be important to identify the vaccination policy most likely to prevent future epidemics. The optimum age for vaccination depends on the rate of decline of maternal antibody, because the presence of antibody reduces vaccine efficacy. The first part of this paper contains a quantitative reappraisal of the data on antibody decline and seroconversion rates by age. The decline in maternal antibody protection follows delayed exponentials, with delays of 2-4 months, and subsequent half-lives of 1-2 months. Using this result in an analytical mathematical model we find that the optimal age to administer a single dose of vaccine to children, which is independent of vaccine coverage, lies within the range 11-19 months. We also show that, where the optimal age cannot be met, it is better to err towards late rather than early vaccination. There are therefore two reasons why developing countries, which presently vaccinate during infancy because measles transmission rates are high should eventually switch to the second year of life. The possible gains from two-dose vaccination schedules are explored with respect to both coverage and efficacy. A two-dose schedule will be beneficial, in principle, only when there is a need to increase net vaccine efficacy, after coverage has been maximized with a one-dose schedule.

Measles control in the United States: problems of the past and challenges for the future

Elimination of indigenous measles from the United States has been a public priority since 1978. To assess the progress made toward this goal, we review the epidemiology of measles from 1963 to the present. From the 1970s through early into the recent measles epidemic, the majority of measles cases were in highly vaccinated, school-age children. This was due primarily to a 1 to 5% primary measles-mumps-rubella vaccine failure rate and nonrandom mixing patterns among school-age populations. To eliminate susceptible individuals in the school-age populations, a second dose of measles vaccine is now recommended between 5 and 6 years or 11 and 12 years by both the Advisory Committee on Immunization Practices and the American Academy of Pediatrics. Later in the epidemic, measles cases surged among unimmunized preschool children, especially among the poor in inner-city areas. Immunization rates have been documented to be low among preschool populations because of missed opportunities to administer vaccines at all health visits and barriers to access to immunizations. To raise immunization rates, the age for the first measles-mumps-rubella immunization was lowered to 12 to 15 months of age, federal immunization funding has increased, and new standards for immunization delivery have been developed and promulgated.

Maternal immunity to measles and infant immunity at less than twelve months of age relative to maternal place of birth

Sera from infants aged 5 to 11 months and from their mothers were used to investigate the level and duration of transplacentally derived measles antibody. The infants of foreign-born, inner-city mothers were more likely to have measles antibody and were less likely to get measles. Infants of foreign-born mothers, because they are less likely to respond to measles vaccine, may require different vaccine strategies than infants of mothers born in the United States.