Meningococcal antibody titres in infants of women immunised with meningococcal polysaccharide vaccine during pregnancy

Prediction of long-term humoral response induced by the two-dose heterologous Ad26.ZEBOV, MVA-BN-Filo vaccine against Ebola

The persistence of the long-term immune response induced by the heterologous Ad26.ZEBOV, MVA-BN-Filo two-dose vaccination regimen against Ebola has been investigated in several clinical trials. Longitudinal data on IgG-binding antibody concentrations were analyzed from 487 participants enrolled in six Phase I and Phase II clinical trials conducted by the EBOVAC1 and EBOVAC2 consortia. A model based on ordinary differential equations describing the dynamics of antibodies and short- and long-lived antibody-secreting cells (ASCs) was used to model the humoral response from 7 days after the second vaccination to a follow-up period of 2 years. Using a population-based approach, we first assessed the robustness of the model, which was originally estimated based on Phase I data, against all data. Then we assessed the longevity of the humoral response and identified factors that influence these dynamics. We estimated a half-life of the long-lived ASC of at least 15 years and found an influence of geographic region, sex, and age on the humoral response dynamics, with longer antibody persistence in Europeans and women and higher production of antibodies in younger participants.

Preventing invasive meningococcal disease in early infancy

This review considers the pathogenesis, diagnosis, and epidemiology of invasive meningococcal disease in infants, to examine and critique meningococcal disease prevention in this population through vaccination. High rates of meningococcal disease and poor outcomes, particularly for very young infants, highlight the importance of meningococcal vaccination in early infancy. Although effective and safe meningococcal vaccines are available for use from 6 weeks of age, they are not recommended globally. Emerging real-world data from the increased incorporation of these vaccines within immunization programs inform recommendations regarding effectiveness, appropriate vaccination schedule, possible long-term safety effects, and persistence of antibody responses. Importantly, to protect infants from IMD, national vaccination recommendations should be consistent with available data regarding vaccine safety, effectiveness, and disease risk.

Maternal vaccination: a review of current evidence and recommendations

Maternal vaccination is an effective means of protecting pregnant women, their fetuses, and infants from vaccine-preventable infections. Despite the availability of sufficient safety data to support the use of vaccines during pregnancy, maternal immunization remains an underutilized method of disease prevention, often because of concerns from both healthcare providers and pregnant women about vaccine safety. Such concerns have been reflected in the low uptake of the COVID-19 vaccine among pregnant women seen in many parts of the world. Here, we present an update of the current recommendations for the use of vaccines during pregnancy, including the evidence supporting the use of novel vaccine platforms. We also provide an overview of the data supporting the use of COVID-19 vaccines in pregnancy and an update of the status of vaccines that are currently under development for use in pregnant women.

Are all vaccines safe for the pregnant traveller? A systematic review and meta-analysis

Pregnant travellers and their offspring are vulnerable to severe outcomes following a wide range of infections. Vaccine-preventable diseases can have a particularly severe course in pregnant women, but little is known about the safety of travel vaccines in pregnant women. We performed a systematic review of all published literature concerning the safety of vaccines frequently given to travellers such as yellow fever, MMR (mumps, measles and rubella), influenza, Tdap (tetanus, diphtheria and pertussis), meningococcus, hepatitis A and B, rabies, polio, typhoid fever, tick-borne encephalitis and Japanese encephalitis vaccines. We included case series, cohort studies and randomized controlled trials (RCTs). For the meta-analysis, we included only RCTs that compared the administration of a vaccine to placebo or to no vaccine. Outcome measures included severe systemic adverse events, maternal outcomes related to the course of pregnancy, neonatal outcomes and local adverse events. We calculated the risk ratio and its 95% confidence interval as the summary measure. The safety of influenza vaccine is supported by high-quality evidence. For Tdap vaccine, no evidence of any harm was found in the meta-analysis of RCTs. A slight increase in chorioamnionitis rate was reported in 3 out of 12 observational studies. However, this small possible risk is far outweighed by a much larger benefit in terms of infant morbidity and mortality. Meningococcal vaccines are probably safe during pregnancy, as supported by RCTs comparing meningococcal vaccines to other vaccines. Data from observational studies support the safety of hepatitis A, hepatitis B and rabies vaccines, as well as that of the live attenuated yellow fever vaccine. We found little or no data about the safety of polio, typhoid, Japanese encephalitis, tick-borne encephalitis and MMR vaccines during pregnancy.

Dynamics of the Humoral Immune Response to a Prime-Boost Ebola Vaccine: Quantification and Sources of Variation

The Ebola vaccine based on Ad26.ZEBOV/MVA-BN-Filo prime-boost regimens is being evaluated in multiple clinical trials. The long-term immune response to the vaccine is unknown, including factors associated with the response and variability around the response. We analyzed data from three phase 1 trials performed by the EBOVAC1 Consortium in four countries: the United Kingdom, Kenya, Tanzania, and Uganda. Participants were randomized into four groups based on the interval between prime and boost immunizations (28 or 56 days) and the sequence in which Ad26.ZEBOV and MVA-BN-Filo were administered. Consecutive enzyme-linked immunosorbent assay (ELISA) measurements of the IgG binding antibody concentrations against the Kikwit glycoprotein (GP) were available for 177 participants to assess the humoral immune response up to 1 year postprime. Using a mathematical model for the dynamics of the humoral response, from 7 days after the boost immunization up to 1 year after the prime immunization, we estimated the durability of the antibody response and the influence of different factors on the dynamics of the humoral response. Ordinary differential equations (ODEs) described the dynamics of antibody response and two populations of antibody-secreting cells (ASCs), short-lived (SL) and long-lived (LL). Parameters of the ODEs were estimated using a population approach. We estimated that half of the LL ASCs could persist for at least 5 years. The vaccine regimen significantly affected the SL ASCs and the antibody peak but not the long-term response. The LL ASC compartment dynamics differed significantly by geographic regions analyzed, with a higher long-term antibody persistence in European subjects. These differences could not be explained by the observed differences in cellular immune response.IMPORTANCE With no available licensed vaccines or therapies, the West African Ebola virus disease epidemic of 2014 to 2016 caused 11,310 deaths. Following this outbreak, the development of vaccines has been accelerated. Combining different vector-based vaccines as heterologous regimens could induce a durable immune response, assessed through antibody concentrations. Based on data from phase 1 trials in East Africa and Europe, the dynamics of the humoral immune response from 7 days after the boost immunization onwards were modeled to estimate the durability of the response and understand its variability. Antibody production is maintained by a population of long-lived cells. Estimation suggests that half of these cells can persist for at least 5 years in humans. Differences in prime-boost vaccine regimens affect only the short-term immune response. Geographical differences in long-lived cell dynamics were inferred, with higher long-term antibody concentrations induced in European participants.

Maternal immunisation to improve the health of HIV-exposed infants

HIV-exposed but uninfected (HEU) infants are at an increased risk of many infectious diseases that can contribute to the high mortality seen among HEU children. Maternal immunisation could be a promising strategy to reduce infections in HEU infants. However, very little research has explored the effect of HIV on the immunogenicity and effectiveness of vaccines given during pregnancy. We review the available evidence on maternal immunisation among women living with HIV (WLWH) for all vaccines recommended, considered, or being investigated for routine or risk-based use during pregnancy. Of the 11 vaccines included, only three have been investigated in WLWH. Available evidence suggests that maternal HIV infection limits the immunogenicity of several vaccines, leaving HEU infants more susceptible to infection during their first few months of life. Whether maternal immunisation reduces the infectious morbidity and mortality associated with infectious diseases in HEU children remains unknown. We conclude the Review by identifying future research priorities.

Malaria in pregnancy shapes the development of foetal and infant immunity

Malaria, particularly Plasmodium falciparum, continues to disproportionately affect pregnant women. In addition to the profoundly deleterious impact of maternal malaria on the health of the mother and foetus, malaria infection in pregnancy has been shown to affect the development of the foetal and infant immune system and may alter the risk of malaria and nonmalarial outcomes during infancy. This review summarizes our current understanding of how malaria infection in pregnancy shapes the protective components of the maternal immune system transferred to the foetus and how foetal exposure to parasite antigens impacts the development of foetal and infant immunity. It also reviews existing evidence linking malaria infection in pregnancy to malaria and nonmalarial outcomes in infancy and how preventing malaria in pregnancy may alter these outcomes. A better understanding of the consequences of malaria infection in pregnancy on the development of foetal and infant immunity will inform control strategies, including intermittent preventive treatment in pregnancy and vaccine development.

Maternal immunization

Pregnant women, neonates, and infants are at higher risk for severe infections due to vaccine-preventable diseases. Very young infants rarely respond well to vaccination due to poor immunogenicity and interference from maternal antibody. Maternal immunization protects the mother and fetus from disease and protects the infant through transplacental antibody transfer through the first 6 months of life. Currently, immunizations routinely recommended during pregnancy include inactivated influenza, tetanus toxoid, and acellular pertussis vaccines. Promising maternal vaccine candidates in development include a group B streptococcus vaccine and a respiratory syncytial virus vaccine. Birth Defects Research 109:379-386, 2017. © 2017 Wiley Periodicals, Inc.

Meningococcal vaccination in pregnancy

Invasive meningococcal disease causes meningitis and septicemia worldwide with highest rates of disease occurring in children <2 years of age, and in particular young infants. Vaccination during pregnancy has been a successful strategy for prevention of other infections in young infants, most notably tetanus, pertussis and influenza. However, few studies of meningococcal vaccines in pregnancy have been undertaken, and none include the most commonly used current vaccines to prevent disease by capsular groups A, B, C, W and Y. The limited data suggest that the older polysaccharide vaccines are immunogenic, but the impact on prevention of infant disease has not been measured. Further studies of MenB protein vaccines and MenA protein-polysaccharide conjugate vaccines in particular are needed if vaccination in pregnancy is to be utilized as an approach to prevention of meningococcal disease in young infants.

Prevalence and decay of maternal pneumococcal and meningococcal antibodies: A meta-analysis of type-specific decay rates

Background

At the time of an infant’s initial vaccination at age ∼2 to 3 months, some infants already have maternal antibodies against vaccine antigens and these can suppress the immune response to vaccination. Modelling the effects of maternal antibody and the timing of infant doses on the antibody response to vaccination, requires estimates of the rate of maternal antibody decay. Decay rates are not well characterised in the medical literature. We investigated variation in the prevalence of maternal anti-capsular pneumococcal and meningococcal antibodies in infants in 14 countries, and estimated type-specific half-lives.

Methods

Individual participant serological data were obtained from clinical trials. Half-lives were estimated from antibody concentrations in infants who did not receive meningococcal or pneumococcal vaccines.

Results

The seroprevalence of maternal pneumococcal antibodies was highest for serotypes 14, and 19F (92% and 80% respectively) and lowest for serotypes 4 and 1 (30% and 34% respectively). Half-life estimates ranged from 38.7 days (95% CI 36.6–41.0) for serotype 6B, to 48.3 days (95% CI 46.7–50.2) for serotype 5. The overall half-life was 42.6 days (95% CI 41.5–43.7). Seroprevalence was highest in Mali, Nigeria, India, and the Philippines, (all >65%) and lowest in the Czech Republic and Finland (both <45%).

In studies of meningococcal vaccines, seroprevalence was 13% for group C (half-life 39.8 days, 95% CI 33.4–49.4) and 43% for group A (half-life 43.1 days 95% CI 39.8–47.2).

Conclusion

Substantial proportions of infants in many countries have antibodies to vaccine serotypes of pneumococcus, however fewer infants have maternally acquired antibodies to groups A and C meningococcus.

Passively-acquired antibodies to capsular polysaccharides decay with a half-life of approximately 6 weeks. These estimates are useful for modelling the impact of proposed vaccination programmes, and consideration of schedules with a delayed start.

Vaccines and Antibodies in Relation to Pregnancy and Lactation

With the rapid pace of immunologic research, it is more important than ever for readers to understand rational immunodiagnosis, immunopro-phylaxis, and immunotherapy. This column is intended to help you ensure proper immunologic drug use in your practice.

Maternal Immunization With an Investigational Trivalent Group B Streptococcal Vaccine: A Randomized Controlled Trial

OBJECTIVE

To evaluate the safety and immunogenicity of an investigational trivalent group B streptococcal vaccine in pregnant women and antibody transfer to their newborns.

METHODS

The primary outcome of this observer-blind, randomized study was to estimate placental antibody transfer rates at birth. Secondary outcomes included measurement of serotype-specific antibodies at screening, 30 days postvaccination, at delivery, and 91 days postpartum, infant antibody levels at 3 months of age, the potential effect on routine infant diphtheria vaccination at 1 month after the third infant series dose, and safety in mother and infant participants through at least 5 months postpartum. Sample size was based on 60 participants in the vaccine group giving a probability of observing at least one adverse event of 90% if the actual rate of the event was 3.8%.

RESULTS

From September 2011 to October 2013, 86 pregnant women were allocated in a 3:2 ratio to receive an investigational group B streptococcal vaccine containing glycoconjugates of serotypes Ia, Ib, and III or placebo. Demographics were similar across groups. Transfer ratios were 66-79% and maternal geometric mean concentrations increased 16-, 23-, and 20-fold by delivery against serotypes Ia, Ib, and III, respectively, Women with no detectable antibodies at inclusion had lower responses than those with detectable antibodies. Three months after birth, infant antibody concentrations were 22-25% of birth levels. Antidiphtheria geometric mean concentrations were similar across groups. In the vaccine and placebo groups, 32 of 51 women (63%) and 26 of 35 women (74%) reported adverse effects, respectively.

CONCLUSION

The investigational vaccine was well-tolerated without safety signals in recipients and their infants or interference with routine infant diphtheria vaccination, although further studies on safety and effectiveness are needed. The investigational vaccine was immunogenic for all serotypes, particularly among women with detectable antibody levels at baseline. Antibody transfer to neonates was at similar levels to other maternally administered polysaccharide vaccines.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov, www.clinicaltrials.gov, NCT01446289.

Maternal immunization: Optimizing protection for the mother and infant

Immunizing the pregnant woman to protect both the mother and her infant from infection has been utilized increasingly over the last decade. New outbreaks of pandemic influenza and the resurgence of pertussis have resulted in policy changes and shifts in health authority recommendations for a number of vaccines aimed to protect both pregnant women and their infants in the first months of life. The ability of maternal immunoglobulin IgG antibodies to be transported readily across the healthy intact placenta depends on many different factors including gestational age in the pregnancy, nature and timing of the immunization and presence of maternal HIV or malaria infections. In this paper, the history of maternal immunization is described, and specifically the studies that prompted the recommendations for tetanus, influenza, pertussis, and, when needed, meningococcus vaccines in pregnant women are reviewed. Ongoing research may result in new maternal vaccines against other pathogens including respiratory syncytial virus and group B streptococcus. Both scientific and regulatory considerations remain challenging in licensure of vaccines specifically for maternal immunization.

Maternal benefits of immunization during pregnancy

The US Centers for Disease Control & Prevention currently recommend routine immunization to prevent 17 vaccine-preventable diseases that occur in infants, children, adolescents, or adults. Pregnant women are at particularly high risk for morbidity and mortality related to several vaccine-preventable diseases. Furthermore, such illnesses are also associated with adverse pregnancy outcomes such as spontaneous abortion, congenital anomalies, preterm birth, and low birthweight. In addition to directly preventing maternal infection, vaccination during pregnancy may offer fetal and infant benefit through passive immunization. Several vaccines aimed at providing passive immunity to neonates are either currently recommended or in development. This article specifically addresses maternal benefits of maternal immunization following (1) vaccines recommended for all pregnant women; (2) vaccines recommended for pregnant women with particular risk factors; and (3) novel vaccines currently under development that primarily aim to at reduce infant morbidity and mortality.

Vaccinations for pregnant women

In the United States, eradication and reduction of vaccine-preventable diseases through immunization has directly increased life expectancy by reducing mortality. Although immunization is a public priority, vaccine coverage among adult Americans is inadequate. The Institute of Medicine, the Community Preventive Services Task Force, and other public health entities have called for the development of innovative programs to incorporate adult vaccination into routine clinical practice. Obstetrician-gynecologists are well suited to serve as vaccinators of women in general and more specifically pregnant women. Pregnant women are at risk for vaccine-preventable disease-related morbidity and mortality and adverse pregnancy outcomes, including congenital anomalies, spontaneous abortion, preterm birth, and low birth weight. In addition to providing direct maternal benefit, vaccination during pregnancy likely provides direct fetal and neonatal benefit through passive immunity (transplacental transfer of maternal vaccine-induced antibodies). This article reviews: 1) types of vaccines; 2) vaccines specifically recommended during pregnancy and postpartum; 3) vaccines recommended during pregnancy and postpartum based on risk factors and special circumstances; 4) vaccines currently under research and development for licensure for maternal-fetal immunization; and 5) barriers to maternal immunization and available patient and health care provider resources.

Safety of immunization during pregnancy: a review of the evidence of selected inactivated and live attenuated vaccines

Vaccine-preventable infectious diseases are responsible for significant maternal, neonatal, and young infant morbidity and mortality. While there is emerging scientific evidence, as well as theoretical considerations, indicating that certain vaccines are safe for pregnant women and fetuses, policy formulation is challenging because of perceived potential risks to the fetus. This report presents an overview of available evidence on pregnant women vaccination safety monitoring in pregnant women, from both published literature and ongoing surveillance programs. Safety data were reviewed for vaccines against diseases which increase morbidity in pregnant women, their fetus or infant as well as vaccines which are used in mass vaccination campaigns against diseases. They include inactivated seasonal and pandemic influenza, mono- and combined meningococcal polysaccharide and conjugated vaccines, tetanus toxoid and acellular pertussis combination vaccines, as well as monovalent or combined rubella, oral poliomyelitis virus and yellow fever vaccines. No evidence of adverse pregnancy outcomes has been identified from immunization of pregnant women with these vaccines.

Maternal immunization

Maternal immunization has the potential to protect the pregnant woman, fetus, and infant from vaccine-preventable diseases. Maternal immunoglobulin G is actively transported across the placenta, providing passive immunity to the neonate and infant prior to the infant's ability to respond to vaccines. Currently inactivated influenza, tetanus toxoid, and acellular pertussis vaccines are recommended during pregnancy. Several other vaccines have been studied in pregnancy and found to be safe and immunogenic and to provide antibody to infants. These include pneumococcus, group B Streptococcus, Haemophilus influenzae type b, and meningococcus vaccines. Other vaccines in development for potential maternal immunization include respiratory syncytial virus, herpes simplex virus, and cytomegalovirus vaccines.

Effectiveness of meningococcal serogroup C vaccine programmes

Since the introduction of monovalent meningococcal serogroup C (MenC) glycoconjugate (MCC) vaccines and the implementation of national vaccination programmes, the incidence of MenC disease has declined markedly as a result of effective short-term vaccination and reduction in acquisition of MenC carriage leading to herd protection. Monovalent and quadrivalent conjugate vaccines are commonly used vaccines to provide protection against MenC disease worldwide. Studies have demonstrated that MCC vaccination confers protection in infancy (0-12 months) from the first dose but this is only short-term. NeisVac-C(®) has the greatest longevity of the currently licensed MCC vaccines in terms of antibody persistence, however antibody levels have been found to fall rapidly after early infant vaccination with two doses of all MCC vaccines - necessitating a booster at ∼12 months. In toddlers, only one dose of the MCC vaccine is required for routine immunization. If herd protection wanes following catch-up campaigns, many children may become vulnerable to infection. This has led many to question whether an adolescent booster is also required.

[Safety update on vaccination during pregnancy]

During influenza A pandemia, the vaccination on pregnant women has raised many questions. Pandemia, easiness of travelling, and insufficient vaccinal coverage, expose these patients to infection which may have serious consequences on their pregnancy and on the child to born. On pregnant women, the precautionary principle is a priority and the evaluation of epidemiological risk is essential, in order to prevent adverses events. Prophylactic vaccinal administration against infections should be assessed with caution due to the little amount of available data. Its use will depend on the vaccine's composition and known side effects, the stage of pregnancy, as well as the benefit for the mother and the child to born, and her clinical history. Whatever the vaccine's nature, its administration never justifies a therapeutic abortion; its evolution must be closely followed to cover the occurrence of complication.

Safety of hepatitis B, pneumococcal polysaccharide and meningococcal polysaccharide vaccines in pregnancy: a systematic review

Immunization during pregnancy has the potential to protect the mother and the newborn from preventable diseases. Current recommendations suggest that inactivated vaccines might be considered during pregnancy when the benefits outweigh the risks. In this review, we aimed to evaluate the safety of hepatitis B (HB) vaccine, pneumococcal polysaccharide vaccine (PPSV) and meningococcal polysaccharide vaccine (MPSV) administration during pregnancy by systematically reviewing the available evidence in PubMed and Scopus databases, as well as postmarketing surveillance data (including the Vaccine Adverse Event Reporting System [VAERS] database). A total of 18 studies were eligible for inclusion in the review. Six studies provided data on HB vaccine, six on PPSV and three on MPSV; three additional studies compared PPSV with MPSV. Additionally, 91 reports on vaccinations of pregnant women were identified from postmarketing surveillance data (88 on HB vaccine, 2 on PPSV, 1 on MPSV). The most common complaints were local reactions, including tenderness and swelling. Overall, immunization during pregnancy did not seem to be associated with a teratogenic effect on the fetus, preterm labour or spontaneous abortion. However, the lack of randomized, placebo-controlled trials, or even large cohort studies, in addition to the inherent limitations of the reviewed observational studies with small statistical power, precluded safe conclusions. Large, prospective, population-based cohort studies are needed to elucidate this issue.

Epstein-Barr virus but not cytomegalovirus is associated with reduced vaccine antibody responses in Gambian infants

BACKGROUND

Epstein-Barr virus (EBV) and cytomegalovirus (CMV) are persistent herpesviruses that have various immunomodulatory effects on their hosts. Both viruses are usually acquired in infancy in Sub-Saharan Africa, a region where childhood vaccines are less effective than in high income settings. To establish whether there is an association between these two observations, we tested the hypothesis that infection with one or both viruses modulate antibody responses to the T-cell independent meningococcal polysaccharide vaccine and the T-cell dependent measles vaccines.

METHODOLOGY/PRINCIPAL FINDINGS

Infection with EBV and CMV was diagnosed by the presence of virus-specific IgM in the peripheral blood or by the presence of IgG at higher levels than that found in umbilical cord blood. Anti-meningococcus IgG and IgM were quantified by ELISA. Anti-measles antibody responses were quantified by haemagglutinin antibody inhibition assay. Infants infected with EBV had reduced IgG and IgM antibody responses to meningococcal polysaccharides and to measles vaccine. Infection with CMV alone predicted no changes in the response to meningococcal polysaccharide. While CMV alone had no discernable effect on the antibody response to measles, the response of infants infected with both CMV and EBV was similar to that of infants infected with neither, suggesting that the effects of CMV infection countered the effects of EBV on measles antibody responses.

CONCLUSIONS

The results of this exploratory study indicate that infection with EBV is associated with reduced antibody responses to polysaccharides and to measles vaccine, but suggest that the response to T-cell dependent antigens such as measles haemagglutinin may be restored by infection with CMV.

Immunity against Neisseria meningitidis serogroup C in the Dutch population before and after introduction of the meningococcal c conjugate vaccine

Background

In 2002 a Meningococcal serogroup C (MenC) conjugate vaccine, with tetanus toxoid as carrier protein, was introduced in the Netherlands as a single-dose at 14 months of age. A catch-up campaign was performed targeting all individuals aged 14 months to 18 years. We determined the MenC-specific immunity before and after introduction of the MenC conjugate (MenCC) vaccine.

Methods and Findings

Two cross-sectional population-based serum banks, collected in 1995/1996 (n = 8539) and in 2006/2007 (n = 6386), were used for this study. The main outcome measurements were the levels of MenC polysaccharide(PS)-specific IgG and serum bactericidal antibodies (SBA) after routine immunization, 4–5 years after catch-up immunization or by natural immunity. There was an increasing persistence of PS-specific IgG and SBA with age in the catch-up immunized cohorts 4–5 years after their MenCC immunization (MenC PS-specific IgG, 0.25 µg/ml (95%CI: 0.19–0.31 µg/ml) at age 6 years, gradually increasing to 2.34 µg/ml,(95%CI: 1.70–3.32 µg/ml) at age 21–22 years). A comparable pattern was found for antibodies against the carrier protein in children immunized above 9 years of age. In case of vaccination before the age of 5 years, PS-specific IgG was rapidly lost. For all age-cohorts together, SBA seroprevalence (≥8) increased from 19.7% to 43.0% in the pre- and post-MenC introduction eras, respectively. In non-immunized adults the SBA seroprevalence was not significantly different between the pre- and post-MenC introduction periods, whereas PS-specific IgG was significantly lower in the post-MenC vaccination (GMT, age ≥25 years, 0.10 µg/ml) era compared to the pre-vaccination (GMT, age ≥25 years, 0.43 µg/ml) era.

Conclusion

MenCC vaccination administered above 5 years of age induced high IgG levels compared to natural exposure, increasing with age. In children below 14 months of age and non-immunized cohorts lower IgG levels were observed compared to the pre-vaccination era, whereas functional levels remained similar in adults. Whether the lower IgG poses individuals at increased risk for MenC disease should be carefully monitored. Large-scale introduction of a MenCC vaccine has led to improved protection in adolescents, but in infants a single-dose schedule may not provide sufficient protection on the long-term and therefore a booster-dose early in adolescence should be considered.

Absence of Neisseria meningitidis serogroup C-specific antibodies during the first year of life in the Netherlands: an age group at risk?

In The Netherlands, a single meningococcal serogroup C conjugate (MenCC) vaccination is administered to children at the age of 14 months. Here, we report the levels of MenC polysaccharide-specific antibodies in children at birth and at 3, 11, and 12 months of age and the presence of functional antibodies at 11 months of age, before infants receive their MenCC immunization. We observed a rapid decline in polysaccharide-specific antibodies after birth and no induction of naturally elicited polysaccharide-specific antibodies. Furthermore, at 11 months of age, no bactericidal antibodies are observed. These data indicate that these infants may be at risk in the period prior to MenCC immunization, if Neisseria meningitidis serogroup C starts to (re)circulate.

Prospects for prevention of childhood infections by maternal immunization

PURPOSE OF REVIEW

To review the literature on using maternal immunization as a strategy to prevent infections in young infants aged below 6 months

RECENT FINDINGS

Maternal immunization continues to reduce the incidence of neonatal tetanus worldwide. Despite increased influenza-related morbidity and mortality in pregnant women and in infants aged less than 6 months, compliance with US recommendations for immunization against influenza in pregnancy is poor. Polysaccharide vaccines against Haemophilus influenzae type b, Streptococcus pneumoniae and Neisseria meningitidis are safe and immunogenic in pregnancy. Protein conjugate vaccines against these infections would be likely to induce higher maternal antibody levels and improve placental transport, thereby further reducing the maternal and infant disease burden. Further studies of acellular pertussis vaccines for use in adolescents and adults should evaluate if maternal immunization could prevent life-threatening pertussis in young infants. Maternal immunization against group B streptococcus is projected to be superior to screening and/or chemoprophylaxis strategies in decreasing infant disease.

SUMMARY

Maternal immunization, with the passage of protective antibody to infants, is a potential strategy to prevent infection in infants who have not completed their primary immunization series from both specific infections of infancy and vaccine-preventable illnesses. Further evaluation of this strategy is supported by medical literature, but liability and educational barriers exist.

Placental and breast transfer of antibodies after maternal immunization with polysaccharide meningococcal vaccine: a randomized, controlled evaluation

We evaluated the strategy of maternal immunization with Neisseria meningitidis (Nm) vaccine in Asian mothers, to assess potential protection of infants, including by breast milk. One hundred and fifty-seven women in the third trimester were randomized to receive a single dose of the polysaccharide Nm (n=75) or a control vaccine (n=82). Group A Nm IgG levels were measured in maternal and infant sera, and specific IgA in breast milk. A 5.6-fold rise of Nm IgG antibody was observed among the Nm vaccinees. At delivery, geometric mean titres (GMTs) of Nm IgG antibody in Nm mothers was 12.5 microg/ml versus 4.97 microg/ml, with a mean infant/maternal antibody ratio of 0.56. Infants of Nm vaccinees had mean IgG levels of 6.9, 2.3, 1.2 and 0.6 microg/ml at 0, 6, 14 and 22 weeks, significantly higher than in control children up to 14 weeks. Anti-Nm IgA levels in milk were 6.8 to 2.0 microg/ml, significantly higher in Nm vaccinees till 6 months. Immunization during pregnancy is safe for both mothers and infants, and provides infants with significantly increased levels of specific IgG for 2-3 months and oral IgA for 6 months.

Maternal vaccines

Acute lower respiratory illness (LRI) is the leading cause of disease worldwide as measured by disability-adjusted life years. New strategies are necessary to decrease the disease burden that is largely borne by infants. Respiratory syncytial virus is the most important cause of LRI in infants. Lower respiratory illness can be prevented by endowing infants with high levels of neutralizing antibodies from mothers whose antibodies are boosted during pregnancy with a potent subunit vaccine. Another important cause of infant mortality is group B streptococcus sepsis in the neonatal period; maternal immunization with a group B conjugate vaccine could prevent this devastating infection.

Vaccines in pregnancy

The concept of maternal immunization to prevent infectious diseases during a period of increased vulnerability in the infant is supported by historical experience and carefully conducted studies of various viral and bacterial vaccines. Candidate vaccines should be minimally reactogenic, immunogenic, and safe. Health education and access to immunization should be a priority if maternal immunization is to succeed as a disease prevention strategy. The potential effect on the incidence of disease in the newborn and young infant can only increase as more candidate vaccines that could be administered during pregnancy become available. In the future, common infections and other, more dreaded diseases, such as herpes simplex virus infection, cytomegalovirus, and human immunodeficiency virus infection, could be prevented with this intervention. Further research on the safety and efficacy of maternal immunization must continue if the occurrence of serious infectious diseases in neonates and young infants is to be reduced.

Conjugated polysaccharide vaccines

The joining of polysaccharide antigens to various proteins can result in increased immunogenicity of vaccines composed of such antigens. This article discusses conjugated polysaccharide vaccines for Haemophilus influenzae, Streptococcus pneumoniae, and Neisseria meningitis. Increased availability and use of such vaccines may result in the ability to give more effective vaccines earlier in life, further reducing the incidence of diseases caused by these organisms.

Placental antibody transfer: influence of maternal HIV infection and placental malaria

AIM

To determine the influence of placental malaria, maternal HIV infection, and maternal hypergammaglobulinaemia on transplacental IgG antibody transfer.

METHODS

One hundred and eighty materno-neonatal pairs from a Malawian population were assessed. Cord and maternal serum samples were tested for total serum IgG antibody titres using nephelometry, and for specific IgG antibody titres to Streptococcus pneumoniae, measles, and tetanus toxoid antibodies using an enzyme linked immunosorbent assay (ELISA).

RESULTS

Multiple regression analyses showed that placental malaria was associated with a decrease in placental IgG antibody transfer to S pneumoniae and measles to 82% and 81%, respectively. Maternal HIV infection was associated with a reduction in IgG antibody transfer to S pneumoniae to 79%; raised maternal total serum IgG titres were correlated with S pneumoniae and measles IgG antibody transfer reduction to 86% and 87%, respectively. No effect was seen with tetanus toxoid antibody transfer.

CONCLUSION

The combined influence of placental malaria, maternal HIV infection, and maternal hypergammaglobulinaemia seems to be linked to the low transplacental antibody transfer observed in the Malawian population.

[Immunologic behavior of meningococcal vaccines]

Meningococcal disease continues to be a great health problem on all continents and the meningococcal vaccines have been proposed for their prevention and epidemic control. The polysaccharide A and C vaccines are relatively efficacious with distinct immunological behavior with regard to the different age groups, however, up to the present no highly efficacious vaccine for meningococcal B disease exists. The meningococcal B capsular polysaccharide is not immunogenic due to the structural mimicry of mammalian tissues and efforts to produce carrier proteins have been proposed in order to obtain an immunogenic vaccine for all age groups that would if possible, protect against all the meningococci. This review of the literature presents the study of the development of the immunological behavior of all the meningococcal vaccines undergoing development and reports on the efforts to obtain a safe and efficacious product for the control of meningococcal disease.

Immunization with a pneumococcal capsular polysaccharide vaccine during pregnancy

The feasibility of preventing invasive pneumococcal infections during the first few months of life by immunization during pregnancy has been investigated. One hundred and fifty Gambian women were immunized with either a 23-valent pneumococcal polysaccharide vaccine or a meningococcal polysaccharide vaccine during the last trimester of pregnancy. Pregnant women showed a good antibody response to five of the six pneumococcal polysaccharides tested (types 1, 3, 5, 6, 14 and 19) but not to type 6 polysaccharide. Mean cord blood/maternal blood IgG antibody ratios varied from 24% (type 1) to 49% (type 3) and differed substantially between individual mother/infant pairs. Pneumococcal antibody levels were higher at birth in infants of women immunized with pneumococcal polysaccharide vaccine than in control infants. However, these antibodies disappeared rapidly during the first few months of life and it is uncertain how much clinical protection against pneumococcal infection maternal immunization would have provided.