Colostrum Obtained from Women Vaccinated with Pneumococcal Vaccine during Pregnancy Inhibits Epithelial Adhesion ofStreptococcus pneumoniae

The protective role of maternal genetic immunization on maternal-fetal health and welfare

Pregnancy is a critical period associated with alterations in physiologic, biologic, and immunologic processes, which can affect maternal-fetal health through development of several infectious diseases. At birth, neonates have an immature immune system that makes them more susceptible to severe viral infections and diseases. For this reason, different maternal nutritional and immunization interventions have been used to improve the immune and health status of the mother and her neonate through passive immunity. Here, we reviewed the protective role of maternal immunization with different types of vaccines, especially genetic vaccines, during pregnancy in maternal-fetal health, immune response, colostrum quality, immune response, and anti-oxidative status. For this purpose, we have used different scientific databases (PubMed and Google Scholar) and other official web pages. We customized the search period range from the year 2000 to 2023 using the key words "maternal immunization" OR "gestation period/pregnancy" OR "genetic vaccination" OR "maternal-fetal health" OR "micronutrients" OR "neonatal immunity" "oxidative stress" OR "colostrum quality". The evidence demonstrated that inactivated or killed vaccines produced significant immune protection in the mother and fetus. Furthermore, most recent studies have suggested that the use of genetic vaccines (mRNA and DNA) during pregnancy is efficient at triggering the immune response in mother and neonate without the risk of undesired pregnancy outcomes. However, factors such as maternal redox balance, nutritional status, and the timing of immunization play essential roles in regulating immune response inflammatory status, antioxidant capacity, and the welfare of both the pregnant mother and her newborn.

Modelling the impact of maternal pneumococcal vaccination on infant pneumococcal disease in low-income settings

Pneumococcal disease is a leading cause of mortality in young children. The largest burden of pneumococcal disease is in the first six months of life before protection from a complete schedule of direct immunisation is possible. Maternal pneumococcal vaccination has been proposed as a strategy for protection in this period of early childhood; however, limited clinical trial data exists. In this study, we developed an age-structured compartmental mathematical model to estimate the impact of maternal pneumococcal vaccination. Our model demonstrates how maternal pneumococcal vaccination could prevent 73% (range 49-88%) of cases in those aged <1 month and 55% (range 36-66%) in those 1-2 months old. This translates to an estimated 17% reduction in deaths due to invasive pneumococcal disease in children under five. Overall, this study demonstrates the potential for maternal pneumococcal vaccination to meaningfully reduce the burden of infant pneumococcal disease, supporting the case for appropriate field-based clinical studies.

Maternal vaccination as an additional approach to improve the protection of the nursling: Anti-infective properties of breast milk

Human milk constitutes a secretion with unique functions of both nourishing the nursling and providing protection against enteric and respiratory infections, mainly due to its content of secretory IgA antibodies but also due to the presence of a plethora of bioactive factors. Specific IgA antibodies are produced locally by plasma cells derived from B lymphocytes that migrate from other mucosae to the mammary gland during lactation, particularly from the gastrointestinal and respiratory tracts. Therefore, here, the authors will provide a comprehensive review of the content and functions of different nutritional and bioactive anti-infectious components from breast milk, such as oligosaccharides, lactoferrin, haptocorrin, α-lactalbumin, k-casein, lysozyme, lactoperoxidase, mucin, fatty acids, defensins, cytokines and chemokines, hormones and growth factors, complement proteins, leukocytes and nucleic acids, including microRNAs, among many others, and the induction of antibody responses in breast milk after maternal vaccination with several licensed vaccines, including the anti-SARS-CoV-2 vaccine preparations used worldwide. Currently, in the midst of the pandemic, maternal vaccination has re-emerged as a crucial source of passive immunity to the neonate through the placenta and breastfeeding, considering that maternal vaccination can induce specific antibodies if performed during pregnancy and after delivery. There have been some reports in the literature about milk IgA antibodies induced by bacterial antigens or inactivated virus vaccines, such as anti-diphtheria-tetanus-pertussis, anti-influenza viruses, anti-pneumococcal and meningococcal polysaccharide preparations. Regarding anti-SARS-CoV-2 vaccines, most studies demonstrate elevated levels of specific IgA and IgG antibodies in milk with virus-neutralizing ability after maternal vaccination, which represents an additional approach to improve the protection of the nursling during the entire breastfeeding period.

Maternal and neonatal pneumococcal vaccination - where are we now?

Pneumococcus is a significant pathogen in neonates and in early infancy, particularly as a cause of invasive disease in sub-Saharan Africa where nasopharyngeal carriage rates are also exceptionally high. The pneumococcal-conjugate vaccines have now been rolled out in many high income settings and an increasing number of low and middle income countries. They have been highly effective at preventing vaccine serotype disease in infants. However, a window of susceptibility remains prior to the first vaccination at around six weeks of age. This paper summarizes the data available on both maternal and neonatal vaccination to prevent disease in newborns and early infancy and considers the key challenges and next steps for research in the field.

Pneumococcal vaccination during pregnancy for preventing infant infection

BACKGROUND

Approximately 450,000 children worldwide die of pneumococcal infections each year. The development of bacterial resistance to antimicrobials adds to the difficulty of treatment of diseases and emphasizes the need for a preventive approach. Newborn vaccination schedules could substantially reduce the impact of pneumococcal disease in immunized children, but do not have an effect on the morbidity and mortality of infants less than three months of age. Pneumococcal vaccination during pregnancy may be a way of preventing pneumococcal disease during the first months of life before the pneumococcal vaccine administered to the infant starts to produce protection.

OBJECTIVES

To assess the effect of pneumococcal vaccination during pregnancy for preventing infant infection.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (31 July 2014) and reference lists of retrieved studies.

SELECTION CRITERIA

Randomized controlled trials in pregnant women comparing pneumococcal vaccine with placebo or doing nothing, or with another vaccine to prevent infant infections.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trials for inclusion and risk of bias, extracted data and checked them for accuracy. We contacted study authors for additional information.

MAIN RESULTS

Seven trials were included, but only six trials (919 participants) contributed data. There was no evidence that pneumococcal vaccination during pregnancy reduces the risk of neonatal infection (risk ratio (RR) 0.66; 95% confidence interval (CI) 0.30 to 1.46; two trials, 241 pregnancies, low quality evidence). Although the data suggest an effect in reducing pneumococcal colonization in infants by 16 months of age (average RR 0.33; 95% CI 0.11 to 0.98; one trial, 56 pregnancies), there was no evidence of this effect in infants at two to three months of age (average RR 1.13; 95% CI 0.46 to 2.78; two trials, 146 pregnancies, low quality evidence) or by six to seven months of age (average RR 0.67, 95% CI 0.22 to 2.08; two trials, 148 pregnancies, low quality evidence). None of the trials included in this review reported neonatal death as a result of pneumococcal infection.Neonatal antibody levels were reported as geometric mean and 95% CI. There were inconsistent results between studies. Two studies showed significantly higher immunoglobulin G (IgG) levels in cord blood in the pneumococcal vaccine group when compared with the control group for all serotypes. In contrast, another trial showed no difference in neonatal antibody levels between the pneumococcal vaccine group and the control group.Maternal antibody levels were also reported as geometric mean and 95% CI. One study showed significantly higher IgG levels in maternal serum in women immunized with pneumococcal vaccine when compared with control vaccine regardless of any serotypes. Another study showed significantly higher maternal antibody levels only for serotype 14, but no evidence of an effect for other serotypes.The percentage of women with seroprotection was measured in one trial at delivery and at 12 months post-delivery. At delivery, results favored the intervention group for serotype 6 (RR 1.49, 95% CI 1.31 to 1.69), serotype 14 (RR 1.40, 95% CI 1.25 to 1.56) and serotype 19 (RR 2.29, 95% CI 1.89 to 2.76). There were no group differences seen at 12 months post-delivery for serotypes 6 or 14 (RR 1.06, 95% CI 1.00 to 1.12 and RR 1.06, 95% CI 0.98 to 1.15, respectively), but results favored the intervention group for serotype 19 (RR 1.59, 95% CI 1.37 to 1.85).No significant difference for tenderness at the injection site between women who received pneumococcal vaccine and those who received control vaccine (average RR 3.20; 95% CI 0.32 to 31.54; two trials, 130 women).The overall quality of evidence is low for primary outcomes. Most outcomes had wide confidence intervals crossing the line of no effect, and most of the included trials had small numbers of participants and few events which led to downgrading evidence for imprecision of findings.

AUTHORS' CONCLUSIONS

There is insufficient evidence to assess whether pneumococcal vaccination during pregnancy could reduce infant infections.

Cooperativity among secretory IgA, the polymeric immunoglobulin receptor, and the gut microbiota promotes host-microbial mutualism

Secretory IgA (SIgA) antibodies in the intestinal tract form the first line of antigen-specific immune defense, preventing access of pathogens as well as commensal microbes to the body proper. SIgA is transported into external secretions by the polymeric immunoglobulin receptor (pIgR). Evidence is reported here that the gut microbiota regulates production of SIgA and pIgR, which act together to regulate the composition and activity of the microbiota. SIgA in the intestinal mucus layer helps to maintain spatial segregation between the microbiota and the epithelial surface without compromising the metabolic activity of the microbes. Products shed by members of the microbial community promote production of SIgA and pIgR by activating pattern recognition receptors on host epithelial and immune cells. Maternal SIgA in breast milk provides protection to newborn mammals until the developing intestinal immune system begins to produce its own SIgA. Disruption of the SIgA-pIgR-microbial triad can increase the risk of infectious, allergic and inflammatory diseases of the intestine.

Breastfeeding after maternal immunisation during pregnancy: providing immunological protection to the newborn: a review

Vaccination during pregnancy results in an augmentation of disease specific maternal antibodies. Immunoglobulin G (IgG) is mainly transferred through the placenta during the third trimester of pregnancy, while secretory Immunoglobulin A (sIgA) is passed through breast milk. At birth, newborns are partially protected against infectious diseases by these antibodies. This review aims to provide an overview of the effect of vaccination during pregnancy on the immunological protection of the newborn by the presence of disease specific sIgA antibodies in breast milk and their possible protective function against disease. Our search produced 11 relevant papers; 1 on pertussis, 7 on pneumococcus, 2 on influenza and 1 on meningococcus. All of the studies in this review that measured disease specific antibodies in breast milk (n=8 papers), stressed the beneficial effect of maternal vaccination during pregnancy on the amount of disease specific sIgA in breast milk. Only a few studies demonstrated a potential protective effect, particularly with influenza vaccines. In an era where maternal vaccination is increasingly considered as a valuable strategy to protect both the mother and infant, further research is needed to assess the effect on breast milk sIgA and to understand the potentially beneficial effects to the infant.

Breast milk: proactive immunomodulation and mucosal protection against viruses and other pathogens

The majority of microorganisms infecting humans cross through the mucosal barrier. This is particularly true in infants who explore the world with their mouths while their immune system is still developing. Human milk not only supplies the nutritional needs of the newborn and protects the baby against infection by confering trophic protection to the intestinal mucosa, but additionally shapes the infant’s gut microbiota and instructs immunomodulation. Reflecting maternal environmental exposition and in virtue of its multiple mechanism of action, secretory IgA in milk exerts a decisive role in direct and cross-protection against a variety of pathogens. Its active role in priming the infant’s immune system is an intriguing hypothesis. From this perspective, breast milk antibodies produced by means of maternal immunization might represent protective and proactive factors able to shape and enhance the infant’s immune responses. Strategies to optimize the benefits of maternal immunization include novel vaccine formulations and mucosal route of delivery.

Pneumococcal antibody concentrations of subjects in communities fully or partially vaccinated with a seven-valent pneumococcal conjugate vaccine

Background

A recent trial with PCV-7 in a rural Gambian community showed reduced vaccine-type pneumococcal carriage in fully vaccinated compared with control communities. We measured pneumococcal polysaccharide antibody concentrations in this trial to understand further the mechanisms underlying the observed changes.

Methods

A single-blind, cluster-randomized (by village) trial was conducted in 21 Gambian villages. In 11 villages, all residents received PCV-7 (Vaccine group); in 10 control villages only children <30 months old or those born during the study received PCV-7. Subjects over the age of 30 months resident in vaccine villages received a single dose of PCV-7 whilst those in control villages received a single dose of a serogroup C meningococcal conjugate vaccine. Serum antibody concentrations against specific pneumococcal polysaccharides were measured in approximately 200 age-stratified subjects before, 4–6, 12 and 24 months following vaccination.

Results

Baseline pneumococcal antibody concentrations were generally high and increased with age up to 10 years. One dose of PCV-7 increased geometric mean antibody concentrations (GMC) in vaccinated versus control villages for vaccine serotypes 6B and 18C, and 4 and 18C, in the young (under 5 years) and older age groups (5+ years) respectively. There were significantly higher proportions of subjects in the vaccinated than in the control communities with an antibody concentration believed to protect against carriage (>5.0 µg/mL) for all but serotype 9V of the PCV-7 serotypes in the older group, but not in the younger age group.

Conclusion

Higher antibodies in vaccinated communities provide an explanation for the lower pneumococcal carriage rates in fully vaccinated compared to control communities.

Trial Registration

Controlled-Trials.com ISRCTN51695599 51695599.

Pneumococcal vaccination during pregnancy for preventing infant infection

BACKGROUND

Each year at least one million children worldwide die of pneumococcal infections. The development of bacterial resistance to antimicrobials adds to the difficulty of treatment of diseases and emphasizes the need for a preventive approach. Newborn vaccination schedules could substantially reduce the impact of pneumococcal disease in immunized children, but does not have an effect on the morbidity and mortality of infants less than three months of age. Pneumococcal vaccination during pregnancy may be a way of preventing pneumococcal disease during the first months of life before the pneumococcal vaccine administered to the infant starts to produce protection.

OBJECTIVES

To assess the effect of pneumococcal vaccination during pregnancy for preventing infant infection.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (31 December 2011) and reference lists of retrieved studies.

SELECTION CRITERIA

Randomized controlled trials in pregnant women comparing pneumococcal vaccine with placebo or doing nothing or with another vaccine to prevent infant infections.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trials for inclusion, methodological quality and extracted data using a data collection form. Data were checked for accuracy. We contacted study authors for additional information.

MAIN RESULTS

Seven trials were included, but only five trials (579 participants) contributed data. There was no evidence that pneumococcal vaccination during pregnancy reduces the risk of neonatal infection (risk ratio (RR) 0.66; 95% confidence interval (CI) 0.30 to 1.46; two trials, 241 pregnancies). Although the data suggest an effect in reducing pneumococcal colonization in infants by 16 months of age (RR 0.33; 95% CI 0.11 to 0.98; one trial, 56 pregnancies), there was no evidence of this effect in infants at two to three months of age (RR 1.13; 95% CI 0.46 to 2.78; two trials, 146 pregnancies) or by six to seven months of age (RR 0.66; 95% CI 0.20 to 2.17; two trials, 144 pregnancies). No significant difference for tenderness at the injection site between women who received pneumococcal vaccine and those who received control vaccine (RR 3.20; 95% CI 0.32 to 31.54; two trials, 130 women).

AUTHORS' CONCLUSIONS

There is insufficient evidence to assess whether pneumococcal vaccination during pregnancy could reduce infant infections.

Immunization of newborns with bacterial conjugate vaccines

Bacterial conjugate vaccines are based on the principle of coupling immunogenic bacterial capsular polysaccharides to a carrier protein to facilitate the induction of memory T-cell responses. Following the success of Haemophilus influenzae type b conjugate vaccines in the 1980s, conjugate vaccines for Streptococcus pneumoniae and Neisseria meningitidis infections were developed and proven to be effective in protecting children against invasive disease. In this review, the use of conjugate vaccines in human newborns is discussed. Neonatal Haemophilus influenzae type b and pneumococcal conjugate vaccination schedules have been trialed and proven to be safe, with the majority of studies demonstrating no evidence for the induction of immune tolerance. Whether their neonatal administration also results in an earlier induction of clinical protection in the first 2-3 critical months of life is still to be demonstrated.

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.

Interleukin 7 from maternal milk crosses the intestinal barrier and modulates T-cell development in offspring

Background

Breastfeeding protects against illnesses and death in hazardous environments, an effect partly mediated by improved immune function. One hypothesis suggests that factors within milk supplement the inadequate immune response of the offspring, but this has not been able to account for a series of observations showing that factors within maternally derived milk may supplement the development of the immune system through a direct effect on the primary lymphoid organs. In a previous human study we reported evidence suggesting a link between IL-7 in breast milk and the thymic output of infants. Here we report evidence in mice of direct action of maternally-derived IL-7 on T cell development in the offspring.

Methods and Findings

We have used recombinant IL-7 labelled with a fluorescent dye to trace the movement in live mice of IL-7 from the stomach across the gut and into the lymphoid tissues. To validate the functional ability of maternally derived IL-7 we cross fostered IL-7 knock-out mice onto normal wild type mothers. Subsets of thymocytes and populations of peripheral T cells were significantly higher than those found in knock-out mice receiving milk from IL-7 knock-out mothers.

Conclusions/Significance

Our study provides direct evidence that interleukin 7, a factor which is critical in the development of T lymphocytes, when maternally derived can transfer across the intestine of the offspring, increase T cell production in the thymus and support the survival of T cells in the peripheral secondary lymphoid tissue.

Mother-infant vaccination with pneumococcal polysaccharide vaccine: persistence of maternal antibodies and responses of infants to vaccination

Protection against pneumococcal infection early in life is needed. This could be achieved by maternal vaccination or by starting infant vaccinations as early as possible. In an open controlled study, pregnant women received both 23-valent pneumococcal polysaccharide vaccine (PPV), Haemophilus influenzae type b conjugate vaccine and tetanus toxoid or tetanus toxoid alone. Infants received PPV at 7 or 17 weeks and the second dose at 3 years of age. Antibodies to six pneumococcal serotypes were measured with the non-22F and 22F enzyme immunoassays (EIA). Elevated antibody concentrations after maternal vaccination persisted in infants until 4 months of age. Infants responded to serotypes 1 and 5, but not to serotypes 6B, 14, 18C and 19F. High maternal antibody concentrations at early age reduced the responses, but not the antibody concentrations, of infants to PPV. The percentages of infants with concentrations >0.35 μg/ml and >1 μg/ml were high at birth, but decreased by age during the first 10 months of life. Revaccination with PPV at 3 years of age induced a good immune response.

Robust vaccine-elicited cellular immune responses in breast milk following systemic simian immunodeficiency virus DNA prime and live virus vector boost vaccination of lactating rhesus monkeys

Breast milk transmission of HIV remains an important mode of infant HIV acquisition. Enhancement of mucosal HIV-specific immune responses in milk of HIV-infected mothers through vaccination may reduce milk virus load or protect against virus transmission in the infant gastrointestinal tract. However, the ability of HIV/SIV strategies to induce virus-specific immune responses in milk has not been studied. In this study, five uninfected, hormone-induced lactating, Mamu A*01(+) female rhesus monkey were systemically primed and boosted with rDNA and the attenuated poxvirus vector, NYVAC, containing the SIVmac239 gag-pol and envelope genes. The monkeys were boosted a second time with a recombinant Adenovirus serotype 5 vector containing matching immunogens. The vaccine-elicited immunodominant epitope-specific CD8(+) T lymphocyte response in milk was of similar or greater magnitude than that in blood and the vaginal tract but higher than that in the colon. Furthermore, the vaccine-elicited SIV Gag-specific CD4(+) and CD8(+) T lymphocyte polyfunctional cytokine responses were more robust in milk than in blood after each virus vector boost. Finally, SIV envelope-specific IgG responses were detected in milk of all monkeys after vaccination, whereas an SIV envelope-specific IgA response was only detected in one vaccinated monkey. Importantly, only limited and transient increases in the proportion of activated or CCR5-expressing CD4(+) T lymphocytes in milk occurred after vaccination. Therefore, systemic DNA prime and virus vector boost of lactating rhesus monkeys elicits potent virus-specific cellular and humoral immune responses in milk and may warrant further investigation as a strategy to impede breast milk transmission of HIV.

Factors associated with pneumococcal carriage in healthy Dutch infants: the generation R study

OBJECTIVE

To study the prevalence, risk factors, and dynamics of pneumococcal carriage in infancy.

STUDY DESIGN

In a population-based prospective cohort study conducted in Rotterdam, the Netherlands between June 2003 and November 2006, nasopharyngeal swabs were obtained from children at age of 1.5, 6, and 14 months. Data on risk factors were obtained from midwives, hospital registries, and questionnaires.

RESULTS

The prevalence of pneumococcal carriage increased from 8.3% at age 1.5 months (n = 627) to 31.3% at age 6 months (n = 832) and 44.5% at age 14 months (n = 757). The prevalence of serotypes covered by the 7-valent conjugate increased from 3.0% to 16.2% and 27.7% at these respective ages. Having siblings (adjusted odds ratio [aOR] = 4.33; 95% confidence interval [CI] = 1.22 to 15.35) and day care attendance (aOR = 3.05, 95% CI = 1.88 to 4.95 at 6 months; aOR = 2.78, 95% CI 1.= 70 to 4.55 at 14 months) were associated with pneumococcal carriage. Pneumococcal carriage at age 6 months was associated with pneumococcal carriage at age 14 months (aOR = 2.43; 95% CI = 1.50 to 3.94). Pneumococcal carriage was not associated with sex, maternal smoking, maternal educational level, or breast-feeding.

CONCLUSIONS

The prevalence of serotypes covered by the 7-valent conjugate vaccine increased in the first year of life. Siblings, day care attendance, and previous pneumococcal carriage were independent factors associated with pneumococcal carriage.

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.

Bacterial pneumonia vaccines and childhood pneumonia: are we winning, refining, or redefining?

Bacterial pneumonia is a substantial cause of childhood morbidity and mortality worldwide, but determination of pathogen-specific burden remains a challenge. In less developed settings, the WHO recommended guidelines are useful for initiating care, but are non-specific. Blood culture has low sensitivity, while radiological findings are non-specific and do not discriminate between viral and bacterial causes of pneumonia. In vaccine probe studies, efficacy is dependent on the specificity of the study outcome to detect pneumonia and the impact of the vaccine on the selected outcome, and may underestimate the true burden of bacterial pneumonia. The rising incidence of antibiotic resistance, emerging respiratory pathogens, potential replacement pneumococcal disease following widespread introduction of pneumococcal polysaccharide-protein conjugate vaccine, the limited specificity of chest radiography, and the poor sensitivity of blood culture are substantial obstacles to accurate surveillance. We provide an overview of the diagnostic challenges of bacterial pneumonia and highlight the need for refining the current diagnostic approach to ensure adequate epidemiological surveillance of childhood pneumonia and the success, or otherwise, of any immunisation strategies.

Pneumococcal vaccination during pregnancy for preventing infant infection

BACKGROUND

Each year at least one million children worldwide die of pneumococcal infections. The development of bacterial resistance to antimicrobials adds to the difficulty of treatment of diseases and emphasizes the need for a preventive approach. Newborn vaccination schedules could substantially reduce the impact of pneumococcal disease in immunized children, but does not have an effect on the morbidity and mortality of infants less than three months of age. Pneumococcal vaccination during pregnancy may be a way of preventing pneumococcal disease during the first months of life before the pneumococcal vaccine administered to the infant starts to produce protection.

OBJECTIVES

To assess the effect of pneumococcal vaccination during pregnancy for preventing infant infection.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group Trials Register (June 2004), CENTRAL (The Cochrane Library, Issue 2, 2004), MEDLINE (January 1966 to June 2004), EMBASE (January 1985 to June 2004), and reference lists of articles.

SELECTION CRITERIA

Randomized controlled trials in pregnant women comparing pneumococcal vaccine with placebo or doing nothing or with another vaccine to prevent infant infections.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed methodological quality and extracted data using a data collection form. Study authors were contacted for additional information.

MAIN RESULTS

Three trials (280 participants) were included. There was no evidence that pneumococcal vaccination during pregnancy reduces the risk of neonatal infection (one trial, 149 pregnancies, relative risk (RR) 0.51; 95% confidence interval (CI) 0.18 to 1.41). Although the data suggest an effect in reducing pneumococcal colonisation in infants by 16 months of age (one trial, 56 pregnancies, RR 0.33; 95% CI 0.11 to 0.98), there was no evidence of this effect in infants at two months of age (RR 0.28; 95% CI 0.02 to 5.11) or by seven months of age (RR 0.32; 95% CI 0.08 to 1.29).

AUTHORS' CONCLUSIONS

There is insufficient evidence to support whether pneumococcal vaccination during pregnancy could reduce infant infections.