Impact of nutritional status on antibody responses to different vaccines in undernourished Gambian children

Vaccine and malnutrition: A narrative review

Nearly 45% of under 5 mortality is directly or indirectly linked to malnutrition. Infection adds to the increased mortality and morbidity in these groups. Vaccination is very important in these undernourished children protecting against life-threatening infections. The goal of vaccination is to produce long-term protection by generating memory cells and the generation of antibodies. Since malnutrition is a state of immunodeficiency, the immune response to vaccines in these children is a matter of concern. We did an exhaustive search to gather more recent studies and corroborated previous findings. Oral Polio Vaccine (OPV), Pneumococcal Polysaccharide Vaccine, Haemophilus influenza vaccine, rabies, and cholera vaccine showed normal response to immunization. Measles and rotavirus vaccines were found to elicit lower seroprotection and lower efficacy in undernourished children. Data regarding response to vaccination against BCG, DPwT, Hepatitis B, pneumococcal conjugate vaccine, and meningococcal vaccine was inconclusive. Although most of the studies show a normal immune response to different vaccines, excluding other confounding factors and effect modifiers had not been easy to interpret. However, with the advances in the understanding of vaccine physiology with newer immunological techniques, good-quality studies might explore the gray areas that remain untouched.

Determination Factors Associated with Immune Responses Towards First Dose Edmonston-Zagreb (EZ) Measles Vaccine in Indonesian Infants

Background:

Measles outbreaks under high coverage of measles vaccination in Indonesia is gaining a necessary evaluation of factors associated with measles-vaccine immune responses.

Objctive:

The purposes of recent study were to evaluate the association of sociodemographic and anthropometric parameters and specific immune responses towards first dose Edmonston-Zagreb (EZ) measles vaccine in Indonesian infants.

Methods:

A total of 35 infants were enrolled in this cohort study. Measles immune responses were followed up at one and six months after vaccination then analyzed for its association with sociodemographic, anthropometric, and nutritional parameters. The plaque-reduction microneutralization assay was conducted to measure the titer of measles specific IgG antibody. The level of CD4⁺ and CD8⁺ T-cells that exhibiting gamma interferon (IFN-γ) secretion were analyzed by flow cytometry. The association between variable was analyzed by linear regression. The difference immune response among variable were analyzed with Mann-Whitney test.

Results:

Vitamin A supplementation and breastfeeding were predicted as associated factor for humoral and cellular immune response after one month and six months measles vaccination among Indonesia Infants.

Conclusion:

Nutritional factor is associated with measles vaccination immune response in Indonesian infants.

The Role of Sex, Ethnicity, Age, and Nutritional Status in the Seropositivity of the Measles Vaccine

AIM: This study investigates the relationship between sex, ethnicity, age, nutritional status with the seropositivity of the Edmonston-Zagreb vaccine in children. METHODS: A cross sectional, observational study was conducted. A total of 45 children were differentiated based on sex, ethnicity, age, and nutritional status when they received the Edmonston-Zagreb measle vaccine for the first time. Flow cytometry was used to look at differences in antibody status as well as populations of CD-4 and CD-8 cells that release IFN- γ. RESULTS: We found no significant differences in antibody levels or CD-4 and CD-8 cell populations that secrete IFN- γ between boys and girls (p > 0.05). Besides, similar results were also confirmed in comparisons between Javanese and Sundanese ethnic groups, 9 months versus more than 9 months of age, or normal versus low body mass index (p > 0.05). CONCLUSIONS: We conclude that sex, race, age, and nutritional status had no effect on immune response to vaccination. As a result, there was no barrier to seroconversion and optimal immunological performance in the children in this trial who received the Edmonston-Zagreb measles vaccination.

Nutritional status positively impacts humoral immunity against its Mycobacterium tuberculosis, disease progression, and vaccine development

Nutritional status contributes to the regulation of immune responses against pathogens, and malnutrition has been considered as a risk factor for tuberculosis (TB). Mycobacterium tuberculosis (Mtb), the causative agent of TB, can modulate host lipid metabolism and induce lipid accumulation in macrophages, where the bacilli adopt a dormant phenotype. In addition, serum lipid components play dual roles in the regulation of and protection from Mtb infection. We analyzed the relationship between nutritional status and the humoral immune response in TB patients. We found that serum HDL levels are positively correlated with the serum IgA specific for Mtb antigens. Analysis of the relationship between serum nutritional parameters and clinical parameters in TB patients showed that serum albumin and CRP levels were negatively correlated before treatment. We also observed reduced serum LDL levels in TB patients following treatment. These findings may provide insight into the role of serum lipids in host immune responses against Mtb infection. Furthermore, improving the nutritional status may enhance vaccination efficacy.

Seasonal variation in the non-specific effects of BCG vaccination on neonatal mortality: three randomised controlled trials in Guinea-Bissau

The BCG vaccine protects non-specifically against other diseases than tuberculosis. Three randomised controlled trials of early BCG in Guinea-Bissau found a 38% reduction in all-cause neonatal mortality. Little is known about the underlying mechanisms. In Guinea-Bissau, prevalent infectious diseases display distinct seasonality. Revisiting the three trials (>6500 infants) comparing early BCG versus no early BCG in low weight infants on all-cause neonatal mortality over 12 consecutive years, we explored the seasonal variation in BCG’s effect on mortality. In a subgroup of participants, adaptive and innate cytokine responses were measured 4 weeks after randomisation. Consistently over the course of the three trials and 12 years, the effect of BCG on all-cause neonatal mortality was particularly beneficial when administered in November to January, coincident with peaking malaria infections. During these months, BCG was also associated with stronger proinflammatory responses to heterologous challenge. Recent studies have suggested a protective effect of BCG against malaria. BCG may also ameliorate immune-compromising fatal effects of placental malaria in the newborn.

Factors That Influence the Immune Response to Vaccination

There is substantial variation between individuals in the immune response to vaccination. In this review, we provide an overview of the plethora of studies that have investigated factors that influence humoral and cellular vaccine responses in humans. These include intrinsic host factors (such as age, sex, genetics, and comorbidities), perinatal factors (such as gestational age, birth weight, feeding method, and maternal factors), and extrinsic factors (such as preexisting immunity, microbiota, infections, and antibiotics). Further, environmental factors (such as geographic location, season, family size, and toxins), behavioral factors (such as smoking, alcohol consumption, exercise, and sleep), and nutritional factors (such as body mass index, micronutrients, and enteropathy) also influence how individuals respond to vaccines. Moreover, vaccine factors (such as vaccine type, product, adjuvant, and dose) and administration factors (schedule, site, route, time of vaccination, and coadministered vaccines and other drugs) are also important. An understanding of all these factors and their impacts in the design of vaccine studies and decisions on vaccination schedules offers ways to improve vaccine immunogenicity and efficacy.

Retinoic acid pre-treatment down regulates V. cholerae outer membrane vesicles induced acute inflammation and enhances mucosal immunity

Bacterial outer membrane vesicles have been extensively investigated and considered as a next generation vaccine. Recently, we have demonstrated that the cholera pentavalent outer membrane vesicles (CPMVs) immunogen induced adaptive immunity and had a strong protective efficacy against the circulating V. cholerae strains in a mouse model. In this present study, we are mainly focusing on reducing outer membrane vesicle (OMV) -mediated toxicity without altering its antigenic property. Therefore, we have selected All-trans Retinoic Acid (ATRA), active metabolites of vitamin A, which have both anti-inflammatory and mucosal adjuvant properties. Pre-treatment of ATRA significantly reduced CPMVs induced TLR2 mediated pro-inflammatory responses in vitro and in vivo. Furthermore, we also found ATRA pre-treatment significantly induced mucosal immune response and protective efficacy after two doses of oral immunization with CPMVs (75µg). This study can help to reduce OMV based vaccine toxicity and induce better protective immunity where children and men suffered from malnutrition mainly in developing countries.

Leptin Elevation as a Risk Factor for Slipped Capital Femoral Epiphysis Independent of Obesity Status

BACKGROUND

Slipped capital femoral epiphysis (SCFE) is strongly associated with childhood obesity, yet the prevalence of obesity is orders of magnitude greater than the prevalence of SCFE. Therefore, it is hypothesized that obesity is not, by itself, a sufficient condition for SCFE, but rather one component of a multifactorial process requiring preexisting physeal pathology. Leptin elevation is seen to varying degrees in patients with obesity, and as leptin has been shown to cause physeal pathology similar to the changes seen in SCFE, we propose that leptin may be a factor distinguishing between patients with SCFE and equally obese children without hip abnormalities.

METHODS

Serum leptin levels were obtained from 40 patients with SCFE and 30 control patients with approximate body mass index (BMI) matching. BMI percentiles were calculated according to Centers for Disease Control and Prevention population data by patient age and sex. Patients were compared by demographic characteristics, leptin levels, odds of leptin elevation, and odds of SCFE.

RESULTS

The odds of developing SCFE was increased by an odds ratio of 4.9 (95% confidence interval [CI], 1.31 to 18.48; p < 0.02) in patients with elevated leptin levels, regardless of obesity status, sex, and race. When grouping patients by their obesity status, non-obese patients with SCFE showed elevated median leptin levels at 5.8 ng/mL compared with non-obese controls at 1.7 ng/mL (p = 0.006). Similarly, obese patients with SCFE showed elevated median leptin levels at 17.9 ng/mL compared with equally obese controls at 10.5 ng/mL (p = 0.039). Serum leptin levels increased in association with obesity (p < 0.001), with an increase in leptin of 0.17 ng/mL (95% CI, 0.07 to 0.27 ng/mL) per BMI percentile point.

CONCLUSIONS

To our knowledge, this study is the first to clinically demonstrate an association between elevated serum leptin levels and SCFE, regardless of BMI. This adds to existing literature suggesting that SCFE is a multifactorial process and that leptin levels may have profound physiological effects on the development of various disease states. Despite a strong association with adiposity, leptin levels vary between patients of equal BMI and may be a vital resource in prognostication of future obesity-related comorbidities.

LEVEL OF EVIDENCE

Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Antibody Responses to Immunizations in Children with Type I Diabetes Mellitus: a Case-Control Study

Type I diabetes mellitus (DM) has been associated with abnormalities of T cells. Our objective was to assess whether antibody responses to T-cell-dependent and -independent antigens in children with DM are lower than those of children without DM. We performed a case-control study matching children with DM to children without DM by age and by assessing antibody levels to pneumococcal serotypes, Haemophilus influenzae, and tetanus and diphtheria toxoids and reassessing antibody levels in patients with antibody levels below protective thresholds after booster immunization. We recruited 36 children with DM and 36 age-matched controls. The mean age was 10 years. There was no difference between groups in antibody levels against the antigens tested. Pneumococcal antibody levels below the protective threshold were found in 35.9% of DM patients after conjugate pneumococcal vaccination with no difference between groups. Booster immunization with unconjugated pneumococcal vaccine resulted in a median level against pneumococcal serotypes of 2.3 μg/ml (range, 0.05 to 664.7 μg/ml) in children with DM and 6.1 μg/ml (0.12 to 203.36 μg/ml) in children without DM (P = 0.013). Over 85% of children had levels above the protective threshold after booster immunization with no difference between groups. There was no evidence for a reduced antibody response to T-cell-dependent antigens given during childhood immunizations in children with DM. There was a reduced antibody response to antigens of pneumococcal strains in children with DM given unconjugated pneumococcal polysaccharide vaccine compared to that of children without DM without being associated with a difference in percentage of antibody levels below the protective threshold between groups.

Malnutrition and vaccination in developing countries

Malnutrition contributes to an estimated 45% of deaths among children under 5 years of age in developing countries, predominantly due to infections. Malnourished children therefore stand to benefit hugely from vaccination, but malnutrition has been described as the most common immunodeficiency globally, suggesting that they may not be able to respond effectively to vaccines. The immunology of malnutrition remains poorly characterized, but is associated with impairments in mucosal barrier integrity, and innate and adaptive immune dysfunction. Despite this, the majority of malnourished children can mount a protective immune response following vaccination, although the timing, quality and duration of responses may be impaired. This paper reviews the evidence for vaccine immunogenicity in malnourished children, discusses the importance of vaccination in prevention of malnutrition and highlights evidence gaps in our current knowledge.

Effects of a Formula Containing Two Types of Prebiotics, Bifidogenic Growth Stimulator and Galacto-oligosaccharide, and Fermented Milk Products on Intestinal Microbiota and Antibody Response to Influenza Vaccine in Elderly Patients: A Randomized Controlled Trial

We investigated the effect of a formula containing two different prebiotics (bifidogenic growth stimulator and galacto-oligosaccharide) and fermented milk products on intestinal microbiota and antibody responses to an influenza vaccine in enterally fed elderly in-patients. Patients were administered either formula containing prebiotics and fermented milk products (group F: n = 12, 79.9 ± 9.5 years old) or standard formula (group C: n = 12, 80.7 ± 10.1 years old) via percutaneous endoscopic gastrostomy during a 14-week intervention period. Subjects were immunized with an influenza vaccine (A/H1N1, A/H3N2, and B) at week 4 of the intervention. Blood biochemical indices, intestinal bacteria populations and antibody titers were analyzed. Bifidobacterium counts increased significantly in group F compared with group C. The enhanced antibody titers against A/H1N1 were maintained in group F for a longer period compared with group C. The titers against A/H3N2 were unchanged between both groups, and those against B were significantly lower in group F than in group C, although few subjects had seroprotective titers against A/H3N2 and B. These results suggest that administration of the formula containing prebiotics and fermented milk products may maintain antibody titers for longer periods through the improvement of intestinal microbiota.

Inflammation and Nutritional Science for Programs/Policies and Interpretation of Research Evidence (INSPIRE)

An increasing recognition has emerged of the complexities of the global health agenda—specifically, the collision of infections and noncommunicable diseases and the dual burden of over- and undernutrition. Of particular practical concern are both 1) the need for a better understanding of the bidirectional relations between nutritional status and the development and function of the immune and inflammatory response and 2) the specific impact of the inflammatory response on the selection, use, and interpretation of nutrient biomarkers. The goal of the Inflammation and Nutritional Science for Programs/Policies and Interpretation of Research Evidence (INSPIRE) is to provide guidance for those users represented by the global food and nutrition enterprise. These include researchers (bench and clinical), clinicians providing care/treatment, those developing and evaluating programs/interventions at scale, and those responsible for generating evidence-based policy. The INSPIRE process included convening 5 thematic working groups (WGs) charged with developing summary reports around the following issues: 1) basic overview of the interactions between nutrition, immune function, and the inflammatory response; 2) examination of the evidence regarding the impact of nutrition on immune function and inflammation; 3) evaluation of the impact of inflammation and clinical conditions (acute and chronic) on nutrition; 4) examination of existing and potential new approaches to account for the impact of inflammation on biomarker interpretation and use; and 5) the presentation of new approaches to the study of these relations. Each WG was tasked with synthesizing a summary of the evidence for each of these topics and delineating the remaining gaps in our knowledge. This review consists of a summary of the INSPIRE workshop and the WG deliberations.

Achieving population-level immunity to rabies in free-roaming dogs in Africa and Asia

Canine rabies can be effectively controlled by vaccination with readily available, high-quality vaccines. These vaccines should provide protection from challenge in healthy dogs, for the claimed period, for duration of immunity, which is often two or three years. It has been suggested that, in free-roaming dog populations where rabies is endemic, vaccine-induced protection may be compromised by immuno-suppression through malnutrition, infection and other stressors. This may reduce the proportion of dogs that seroconvert to the vaccine during vaccination campaigns and the duration of immunity of those dogs that seroconvert. Vaccination coverage may also be limited through insufficient vaccine delivery during vaccination campaigns and the loss of vaccinated individuals from populations through demographic processes. This is the first longitudinal study to evaluate temporal variations in rabies vaccine-induced serological responses, and factors associated with these variations, at the individual level in previously unvaccinated free-roaming dog populations. Individual-level serological and health-based data were collected from three cohorts of dogs in regions where rabies is endemic, one in South Africa and two in Indonesia. We found that the vast majority of dogs seroconverted to the vaccine; however, there was considerable variation in titres, partly attributable to illness and lactation at the time of vaccination. Furthermore, >70% of the dogs were vaccinated through community engagement and door-to-door vaccine delivery, even in Indonesia where the majority of the dogs needed to be caught by net on successive occasions for repeat blood sampling and vaccination. This demonstrates the feasibility of achieving population-level immunity in free-roaming dog populations in rabies-endemic regions. However, attrition of immune individuals through demographic processes and waning immunity necessitates repeat vaccination of populations within at least two years to ensure communities are protected from rabies. These findings support annual mass vaccination campaigns as the most effective means to control canine rabies.

Undernutrition, the acute phase response to infection, and its effects on micronutrient status indicators

Infection and undernutrition are prevalent in developing countries and demonstrate a synergistic relation. Undernutrition increases infection-related morbidity and mortality. The acute phase response (APR) is an innate, systemic inflammatory reaction to a wide array of disruptions in a host's homeostasis, including infection. Released from immune cells in response to deleterious stimuli, proinflammatory cytokines act on distant tissues to induce behavioral (e.g., anorexia, weakness, and fatigue) and systemic effects of the APR. Cytokines act to increase energy and protein requirements to manifest fever and support hepatic acute phase protein (APP) production. Blood concentrations of glucose and lipid are augmented to provide energy to immune cells in response to cytokines. Additionally, infection decreases intestinal absorption of nutrients and can cause direct loss of micronutrients. Traditional indicators of iron, zinc, and vitamin A status are altered during the APR, leading to inaccurate estimations of deficiency in populations with a high or unknown prevalence of infection. Blood concentrations of APPs can be measured in nutrition interventions to assess the time stage and severity of infection and correct for the APR; however, standardized cutoffs for nutrition applications are needed. Protein-energy malnutrition leads to increased gut permeability to pathogens, abnormal immune cell populations, and impaired APP response. Micronutrient deficiencies cause specific immune impairments that affect both innate and adaptive responses. This review describes the antagonistic interaction between the APR and nutritional status and emphasizes the need for integrated interventions to address undernutrition and to reduce disease burden in developing countries.

Zinc treatment ameliorates diarrhea and intestinal inflammation in undernourished rats

BACKGROUND

WHO guidelines recommend zinc supplementation as a key adjunct therapy for childhood diarrhea in developing countries, however zinc's anti-diarrheal effects remain only partially understood. Recently, it has been recognized that low-grade inflammation may influence stunting. In this study, we examined whether oral zinc supplementation could improve weight, intestinal inflammation, and diarrhea in undernourished weanling rats.

METHODS

Rats were undernourished using a northeastern Brazil regional diet (RBD) for two weeks, followed by oral gavage with a saturated lactose solution (30 g/kg) in the last 7 days to induce osmotic diarrhea. Animals were checked for diarrhea daily after lactose intake. Blood was drawn in order to measure serum zinc levels by atomic absorption spectroscopy. Rats were euthanized to harvest jejunal tissue for histology and cytokine profiles by ELISA. In a subset of animals, spleen samples were harvested under aseptic conditions to quantify bacterial translocation.

RESULTS

Oral zinc supplementation increased serum zinc levels following lactose-induced osmotic diarrhea. In undernourished rats, zinc improved weight gain following osmotic diarrhea and significantly reduced diarrheal scores by the third day of lactose intake (p < 0.05), with improved jejunum histology (p < 0.0001). Zinc supplementation diminished bacterial translocation only in lactose-challenged undernourished rats (p = 0.03) compared with the untreated challenged controls and reduced intestinal IL-1β and TNF-α cytokines to control levels.

CONCLUSION

Altogether our findings provide novel mechanisms of zinc action in the setting of diarrhea and undernutrition and support the use of zinc to prevent the vicious cycle of malnutrition and diarrhea.

Vaccination of the immunocompromised child

The development of vaccination is a major achievement in modern medicine. However, children treated with immunosuppression may not at all, or only in part, receive routine immunization due to uncertainty of its risks and effect. There is a substantial lack of pediatric studies concerning the efficacy and safety of vaccination in this patient group. Experience from similar adult groups and children with HIV infection can be used as a model for other disease categories. With increasing knowledge of the immunologic basis of vaccination and how immunosuppressive drugs interfere with the immune system, improved vaccines could be tailored, and adequate, individualized guidelines issued.

Gestational zinc deficiency impairs humoral and cellular immune responses to hepatitis B vaccination in offspring mice

Background

Gestational zinc deficiency has been confirmed to impair the infant immune function. However, knowledge about effects of maternal mild zinc deficiency during pregnancy on hepatitis B vaccine responsiveness in offspring is limited. In this report, we aimed to examine how maternal zinc deficiency during pregnancy influences humoral and cellular immune responses to hepatitis B vaccination in offspring of BALB/c mice.

Methodology/Principal Findings

From day 1 of pregnancy upon delivery, maternal mice were given a standard diet (30 mg/kg/day zinc), zinc deficient diet (8 mg/kg/day zinc), or combination of zinc deficient diet (8 mg/kg/day zinc in the first 2 weeks of gestation) and zinc supplement diet (150 mg/kg/day zinc for the last week of pregnancy), respectively. Newborn pups of these maternal mice were immunized with hepatitis B vaccine at postnatal weeks 0, 2 and 4. Then, splenocytes and blood samples from the offspring mice were harvested for detection of serum zinc concentrations, humoral and cell-mediated immune responses, expression of cytokines using ELISA, CCK-8 and flow cytometric analysis. Results from the present study demonstrated that gestational zinc deficiency inhibited antibody responses, and decreased the proliferative capacity of T cells in offsprings immunized with hepatitis B vaccine. Additionally, HBsAg-specific cytokines analysis revealed that gestational zinc deficiency could inhibit secretion of IFN-γ from splenocytes, and decrease IFN-γ expression of CD4⁺ and CD8⁺ T cells.

Conclusions/Significance

Gestational zinc deficiency can weaken the humoral and cell-mediated immune responses to hepatitis B vaccine via decreasing B cell counts and hepatitis B virus-specific immunoglobulin G production, as well as reducing T cell proliferation, CD4⁺/CD8⁺ T cell ratio, and Th1-type immune responses.

Detecting Foci of Malaria Transmission with School Surveys: A Pilot Study in the Gambia

BACKGROUND

In areas of declining malaria transmission such as in The Gambia, the identification of malaria infected individuals becomes increasingly harder. School surveys may be used to identify foci of malaria transmission in the community.

METHODS

The survey was carried out in May-June 2011, before the beginning of the malaria transmission season. Thirty two schools in the Upper River Region of The Gambia were selected with probability proportional to size; in each school approximately 100 children were randomly chosen for inclusion in the study. Each child had a finger prick blood sample collected for the determination of antimalarial antibodies by ELISA, malaria infection by microscopy and PCR, and for haemoglobin measurement. In addition, a simple questionnaire on socio-demographic variables and the use of insecticide-treated bed nets was completed. The cut-off for positivity for antimalarial antibodies was obtained using finite mixture models. The clustered nature of the data was taken into account in the analyses.

RESULTS

A total of 3,277 children were included in the survey. The mean age was 10 years (SD = 2.7) [range 4-21], with males and females evenly distributed. The prevalence of malaria infection as determined by PCR was 13.6% (426/3124) [95% CI = 12.2-16.3] with marked variation between schools (range 3-25%, p<0.001), while the seroprevalence was 7.8% (234/2994) [95%CI = 6.4-9.8] for MSP119, 11.6% (364/2997) [95%CI = 9.4-14.5] for MSP2, and 20.0% (593/2973) [95% CI = 16.5-23.2) for AMA1. The prevalence of all the three antimalarial antibodies positive was 2.7% (79/2920).

CONCLUSIONS

This survey shows that malaria prevalence and seroprevalence before the transmission season were highly heterogeneous.

Low immune response to hepatitis B vaccine among children in Dakar, Senegal

HBV vaccine was introduced into the Expanded Programme on Immunization (EPI) in Senegal and Cameroon in 2005. We conducted a cross-sectional study in both countries to assess the HBV immune protection among children. All consecutive children under 4 years old, hospitalized for any reason between May 2009 and May 2010, with an immunisation card and a complete HBV vaccination, were tested for anti-HBs and anti-HBc. A total of 242 anti-HBc-negative children (128 in Cameroon and 114 in Senegal) were considered in the analysis. The prevalence of children with anti-HBs ≥10 IU/L was higher in Cameroon with 92% (95% CI: 87%–97%) compared to Senegal with 58% (95% CI: 49%–67%), (p<0.001). The response to vaccination in Senegal was lower in 2006–2007 (43%) than in 2008–2009 (65%), (p = 0.028). Our results, although not based on a representative sample of Senegalese or Cameroonian child populations, reveal a significant problem in vaccine response in Senegal. This response problem extends well beyond hepatitis B: the same children who have not developed an immune response to the HBV vaccine are also at risk for diphtheria, tetanus, pertussis (DTwP) and Haemophilus influenzae type b (Hib). Field biological monitoring should be carried out regularly in resource-poor countries to check quality of the vaccine administered.

Cost-effectiveness of rotavirus vaccination in Bolivia from the state perspective

BACKGROUND

In Bolivia, in 2008, the under-five mortality rate is 54 per 1000 live births. Diarrhea causes 15% of these deaths, and 40% of pediatric diarrhea-related hospitalizations are caused by rotavirus illness (RI). Rotavirus vaccination (RV), subsidized by international donors, is expected to reduce morbidity, mortality, and economic burden to the Bolivian state. Estimates of illness and economic burden of RI and their reduction by RV are essential to the Bolivian state's policies on RV program financing. The goal of this report is to estimate the economic burden of RI and the cost-effectiveness of the RV program.

METHODS

To assess treatment costs incurred by the healthcare system, we abstracted medical records from 287 inpatients and 6751 outpatients with acute diarrhea between 2005 and 2006 at 5 sentinel hospitals in 4 geographic regions. RI prevalence rates were estimated from 4 years of national hospital surveillance. We used a decision-analytic model to assess the potential cost-effectiveness of universal RV in Bolivia.

RESULTS

Our model estimates that, in a 5-year birth cohort, Bolivia will incur over US$3 million in direct medical costs due to RI. RV reduces, by at least 60%, outpatient visits, hospitalizations, deaths, and total direct medical costs associated with rotavirus diarrhea. Further, RV was cost-savings below a price of US$3.81 per dose and cost-effective below a price of US$194.10 per dose. Diarrheal mortality and hospitalization inputs were the most important drivers of rotavirus vaccine cost-effectiveness.

DISCUSSION

Our data will guide Bolivia's funding allocation for RV as international subsidies change.

Failure to thrive in childhood

BACKGROUND

Failure to thrive impairs children's weight gain and growth, their defenses against infection, and their psychomotor and intellectual development.

METHODS

This paper is a review of pertinent articles that were published from 1995 to October 2010 and contained the terms "failure to thrive", "underweight", "malnutrition", "malabsorption", "maldigestion" and "refeeding syndrome". The articles were retrieved by a search in the PubMed and Cochrane Library databases.

RESULTS

In developed countries, failure to thrive is usually due to an underlying disease. The degree of malnutrition is assessed with anthropometric techniques. For each patient, the underlying disease must be identified and the mechanism of failure to thrive understood, so that proper medical and nutritional treatment can be provided. Nutritional treatment involves either giving more food, or else raising the caloric density of the patient's food. Liquid formulas can be given as a supplement to normal meals or as balanced or unbalanced tube feeds; they can be given orally, through a nasogastric tube, or through a gastrostomy tube. Severely malnourished children with poor oral intake should be treated with parenteral nutrition. To avoid refeeding syndrome in severely malnourished children, food intake should be increased slowly at first, and phosphate, magnesium, and potassium supplements should be given.

CONCLUSION

The proper treatment of failure to thrive in childhood consists of treatment of the underlying illness, combined with nutritional treatment that addresses the mechanism of the accompanying failure to thrive.

Immunological mechanisms of vaccination

Vaccines represent one of the greatest triumphs of modern medicine. Despite the common origins of vaccinology and immunology more than 200 years ago, the two disciplines have evolved along such different trajectories that most of the highly successful vaccines have been made empirically, with little or no immunological insight. Recent advances in innate immunity have offered new insights about the mechanisms of vaccine-induced immunity and have facilitated a more rational approach to vaccine design. Here we will discuss these advances and emerging themes on the immunology of vaccination.

The use of dried blood spots for assessing antibody response to hepatitis A virus after natural infection and vaccination

During recent years, vaccination against hepatitis A has been implemented in several countries. It is expected that the increase in mass vaccination against hepatitis A will eventually result in a decreased prevalence of anti-HAV antibodies in the general population. For this reason, a suitable clinical sample for diagnosis of hepatitis A must be sufficiently sensitive to enable detection of lower antibodies titers. In this study, the feasibility of using dried blood spots (DBS) was assessed for the detection of anti-HAV antibodies after a natural infection and vaccination. Seventy-four DBS and paired plasma samples were obtained from a group of college students for a cross-sectional hepatitis A seroepidemiological study. Forty-six students seronegative for anti-HAV were selected randomly and immunized with an inactivated hepatitis A vaccine using an 0-6 month schedule. Seroconversion was monitored in paired plasma and DBS samples 6 months after the first dose followed by a period of 8 and 24 months after the second dose. A strong correlation between OD/CO rates of paired plasma and DBS samples for the detection of anti-HAV was observed. The sensitivity and specificity of the DBS compared with plasma for the detection of anti-HAV antibodies after natural infection was 100%. The sensitivity of DBS in samples collected 24 months after the second dose of hepatitis A vaccine was 95.4%. The results showed that DBS samples can be used for the detection of anti-HAV antibodies both after natural infection or vaccination.

Equivalence between pre-exposure schemes for human rabies and evaluation of the need for serological monitoring

OBJECTIVE

To evaluate the humoral immune response to the pre-exposure schedule of human rabies vaccination through intradermal and intramuscular routes, as well as the need for serological monitoring.

METHODS

A randomized and controlled intervention study was carried out in São Paulo, Southeastern Brazil, from 2004-2005. There were 149 volunteers, of which 127 completed the vaccination schedule (65 intradermal and 62 intramuscular) and underwent humoral immune response evaluation at ten, 90 and 180 days post-vaccination. Two outcomes were considered for comparing the two routes of administration: the geometric average of neutralizing antibody titers and the proportion of individuals with satisfactory titers (> 0.5 IU/mL) at each evaluation point. The association of the humoral immune response with anthropometric and demographic data was analyzed through a normal distribution test and a chi-square test with a Yates correction. After completion of the vaccination schedule, the proportion of seropositive results was compared by the Kruskall Wallis test, and the average titers were compared by variance analysis.

RESULTS

the average antibody titers were higher in patients who were vaccinated intramuscularly. The percentage of volunteers with satisfactory titers (> 0.5% IU/mL) decreased over time in both groups. However, in the group vaccinated intradermally the rate of satisfactory titers on day 180 ranged from 20% to 25%, while the intramuscular route varied from 63% to 65%. An association between the humoral immune response and the demographic and anthropometric variables was not observed.

CONCLUSIONS

Serology after the third dose can be considered unnecessary in unexposed patients, since 97% and 100% of volunteers respectively vaccinated by the intradermal and intramuscular route presented satisfactory antibody levels (> 0.5% IU/mL).

Heterogeneity in malaria exposure and vaccine response: implications for the interpretation of vaccine efficacy trials

Background

Phase III trials of the malaria vaccine, RTS, S, are now underway across multiple sites of varying transmission intensity in Africa. Heterogeneity in exposure, vaccine response and waning of efficacy may bias estimates of vaccine efficacy.

Methods

Theoretical arguments are used to identify the expected effects of a) heterogeneity in exposure to infectious bites; b) heterogeneity in individual's response to the vaccine; and c) waning efficacy on measures of vaccine efficacy from clinical trials for an infection-blocking vaccine.

Results

Heterogeneity in exposure and vaccine response leads to a smaller proportion of trial participants becoming infected than one would expect in a homogeneous setting. This causes estimates of vaccine efficacy from clinical trials to be underestimated if transmission heterogeneity is ignored, and overestimated if heterogeneity in vaccine response is ignored. Waning of vaccine efficacy can bias estimates of vaccine efficacy in both directions.

Conclusions

Failure to account for heterogeneities in exposure and response, and waning of efficacy in clinical trials can lead to biased estimates of malaria vaccine efficacy. Appropriate methods to reduce these biases need to be used to ensure accurate interpretation and comparability between trial sites of results from the upcoming Phase III clinical trials of RTS, S.

Landscape analysis of interactions between nutrition and vaccine responses in children

The world's poorest children are likely to be malnourished when receiving their childhood vaccines. It is uncertain whether this affects vaccine efficacy and whether the coadministration of nutrient supplements with vaccines has beneficial or detrimental effects. More recently, a detrimental interaction between vitamin A (VA) supplementation (VAS) and the killed diphtheria-tetanus-pertussis vaccine given in early childhood has been suggested. This report provides a critical review of the published interactions between nutritional status and/or supplementation and vaccine responses in children. Due to an absence of evidence for most nutrients, this analysis focused on protein-energy, vitamins A and D, and iron and zinc. All vaccines were considered. Both observational studies and clinical trials that led to peer-reviewed publications in English or French were included. These criteria led to a pool of 58 studies for protein-energy malnutrition, 43 for VA, 4 for vitamin D, 10 for iron, and 22 for zinc. Our analysis indicates that malnutrition has surprisingly little or no effect on vaccine responses. Evidence for definitive adjunctive effects of micronutrient supplementation at the time of vaccination is also weak. Overall, the paucity, poor quality, and heterogeneity of data make it difficult to draw firm conclusions. The use of simple endpoints that may not correlate strongly with disease protection adds uncertainty. A detailed examination of the immunological mechanisms involved in potential interactions, employing modern methodologies, is therefore required. This would also help us understand the proposed, but still unproven, negative interactions between VAS and vaccine safety, a resolution of which is urgently required.

Dietary restriction abrogates antibody production induced by a DNA vaccine encoding the mycobacterial 65 kDa heat shock protein

Background

Protein-calorie malnutrition (PCM) is the most common type of malnutrition. PCM leads to immunodeficiency and consequent increased susceptibility to infectious agents. In addition, responses to prophylactic vaccines depend on nutritional status. This study aims to evaluate the ability of undernourished mice to mount an immune response to a genetic vaccine (pVAXhsp65) against tuberculosis, containing the gene coding for the heat shock protein 65 from mycobacteria.

Methods

Young adult female BALB/c mice were fed ad libitum or with 80% of the amount of food consumed by a normal diet group. We initially characterized a mice model of dietary restriction by determining body and spleen weights, hematological parameters and histopathological changes in lymphoid organs. The ability of splenic cells to produce IFN-gamma and IL-4 upon in vitro stimulation with LPS or S. aureus and the serum titer of specific IgG1 and IgG2a anti-hsp65 antibodies after intramuscular immunization with pVAXhsp65 was then tested.

Results

Dietary restriction significantly decreased body and spleen weights and also the total lymphocyte count in blood. This restriction also determined a striking atrophy in lymphoid organs as spleen, thymus and lymphoid tissue associated with the small intestine. Specific antibodies were not detected in mice submitted to dietary restriction whereas the well nourished animals produced significant levels of both, IgG1 and IgG2a anti-hsp65.

Conclusion

20% restriction in food intake deeply compromised humoral immunity induced by a genetic vaccine, alerting, therefore, for the relevance of the nutritional condition in vaccination programs based on these kinds of constructs.

A meta-analysis of leptin reference ranges in the healthy paediatric prepubertal population

Objective

The initial discovery of leptin (1994) has given rise to a substantial number of published studies. This study aimed at identifying the published data on the reference ranges of total, free and bound leptin concentration in the healthy prepubertal population.

Methods

A search was conducted on original English language studies published from 1994 to 2005 in the following databases: PubMed ( n = 58), EMBASE ( n = 4), Biological Abstracts ( n = 2) and Science Finder Scholar ( n = 66). A cited reference search was completed in Science Citation Index on studies with a leptin range. A meta-analysis was completed on included studies containing a dataset and a sample size for a leptin concentration range and/or mean±standard deviation for a healthy prepubertal population. Preanalytical and analytical variations were examined. Preanalytical variables included aspects such as fasting state and gender, while analytical variation comprised the type of leptin assay methodology.

Results

Twelve studies met the inclusion criteria. One study examined free leptin; 11 studies examined total concentration. No studies reported leptin reference ranges established by Clinical and Laboratory Standards Institute (CLSI) criteria, although four studies reported specific study leptin ranges. The methodology of enzyme-linked immunosorbent assay demonstrated a wider leptin range than radio immunoassay (0.56–36.35 vs. 1.01–12.21 ng/mL). Males had a significantly lower mean leptin concentration than females ( P = 0.0006); obese children had a higher concentration than non-obese ( P = 0.0001).

Conclusion

No studies have established CLSI-based leptin reference ranges in prepubertal healthy children and there is a wide variation in the published leptin concentrations. These differences suggest that caution should be used in the interpretation and comparison between studies.

Immunogenicity and serotype-specific efficacy of a 9-valent pneumococcal conjugate vaccine (PCV-9) determined during an efficacy trial in The Gambia

This study aimed to determine the immunogenicity of a 9-valent pneumococcal conjugate vaccine (PCV-9) in a subgroup of Gambian children enrolled in a large vaccine efficacy trial. To place the antibody results in context, in this paper we also report previously unpublished data on serotype-specific clinical vaccine efficacy from the main trial. In the sub-study, a single 2-4 ml venous blood specimen was collected from 212 Gambian children 4-6 weeks after the administration of a third dose of PCV-9 or placebo. IgG antibodies to pneumococcal serotype 1, 4, 5, 6B, 9V, 14, 18C, 19F and 23F polysaccharides were measured by ELISA. The proportions of infants with antibody concentrations above 0.2, 0.35 and 1.0 microg/ml, and the geometric mean concentrations (GMCs) of anti-pneumococcal polysaccharide antibodies were substantially higher for each serotype in children who received three doses of PCV-9 than those in the placebo group. Among PCV-9 recipients, GMCs ranged between 2.61 and 11.09 microg/ml with the highest being against serotype 14 and the lowest against 9V polysaccharide. The estimated overall protective antibody level for all nine serotypes, based on the vaccine efficacy against vaccine-type invasive pneumococcal disease (IPD) of 77% (95% CI: 51, 90) observed in the trial, was 2.3 microg/ml (95% CI: 1.0, 5.0). The PCV-9 studied was immunogenic in a Gambian population where it was also found to be efficacious.

Sexual dimorphism of humoral immunity with human vaccines

It has been contended that limited data exist on sex-difference in immune response with vaccines in humans. However, a comprehensive search of the literature retrieved 97 studies with 14 vaccines influenza (7 studies), hepatitis A (15 studies), hepatitis B (50 studies), pnuemococcal polysaccaride (4 studies), diphtheria (4 studies), rubella (3 studies), measles (2 studies), yellow fever (3 studies), meningococcal A (1 study), meningococcal C (1 study), tetanus (1 study), brucella (1 study), Venezuelan equine encephalitis (1 study) and rabies (4 studies), with sex-difference in humoral (antibody) response. These differences are associated with sex-difference in the clinical efficacy of influenza, hepatitis A, hepatitis B, pneumococcal polysaccharide and diphtheria vaccines and significant adverse reactions with rubella, measles and yellow fever vaccines. The genesis of these differences is uncertain but not entirely related to gonadal hormones (differences are seen in pre-pubertal and post-menopausal subjects not on hormone replacement therapy) or female sex (males had greater serological response for pneumococcal, diphtheria, yellow fever, Venezuelan equine encephalitis and in some studies with rabies vaccine. As sex-difference in humoral immune response was seen with most vaccines which cover the spectrum of mechanisms by which infectious agents cause disease (mucosal replication, viral viraemia, bacterial bacteraemia, toxin production and neuronal invasion), it is mandatory that vaccine trialists recruit a representative sample of females and males to be able to assess sex-differences which may have clinical implications.

Birth season and environmental influences on blood leucocyte and lymphocyte subpopulations in rural Gambian infants

BACKGROUND

In rural Gambia, birth season predicts infection-related adult mortality, providing evidence that seasonal factors in early life may programme immune development. This study tested whether lymphocyte subpopulations assessed by automated full blood count and flow cytometry in cord blood and at 8, 16 and 52 weeks in rural Gambian infants (N = 138) are affected by birth season (DRY = Jan-Jun, harvest season, few infections; WET = Jul-Dec, hungry season, many infections), birth size or micronutrient status.

RESULTS

Geometric mean cord and postnatal counts were higher in births occurring in the WET season with both season of birth and season of sampling effects. Absolute CD3+, CD8+, and CD56+ counts, were higher in WET season births, but absolute CD4+ counts were unaffected and percentage CD4+ counts were therefore lower. CD19+ counts showed no association with birth season but were associated with concurrent plasma zinc status. There were no other associations between subpopulation counts and micronutrient or anthropometric status.

CONCLUSION

These results demonstrate a seasonal influence on cell counts with a disproportionate effect on CD8+ and CD56+ relative to CD4+ cells. This seasonal difference was seen in cord blood (indicating an effect in utero) and subsequent samples, and is not explained by nutritional status. These findings are consistent with the hypothesis than an early environmental exposure can programme human immune development.

Zinc supplementation of pregnant rats with adequate zinc nutriture suppresses immune functions in their offspring

The knowledge about consequences of marginal zinc (Zn) deficiency and Zn supplementation during pregnancy on immune function in the offspring is limited. The aim of this study was to examine whether effects of mild Zn deficiency and subsequent Zn supplementation during pregnancy persist after weaning and affect immune function of the offspring. Adult female rats were fed a Zn-adequate diet (ZC, n = 8) or a Zn-deficient diet (ZD, n = 8) from preconception through lactation. Pregnant rats were supplemented with either Zn (1.5 mg Zn in water) or placebo (water) 3 times/wk throughout pregnancy. Pups were orally immunized with cholera toxin and bovine serum albumin-dinitrophenol (DNP) 3 times at weekly intervals and killed 1 wk after the last dose. Proliferation and cytokine responses in lymphocytes from Payer's patches and spleen, and antigen specific antibodies in serum were studied. Zn supplementation of ZD dams led to enhanced lymphocyte proliferation and IFN-gamma responses in pups ZDZ+. In contrast, Zn supplementation of ZC dams suppressed these responses in pups ZCZ+. Total and DNP-specific IgA responses were lower in pups of the Zn-deficient group compared with the Zn-adequate group. Relative thymus weight was greater in the pups (ZDZ-) of ZD placebo-supplemented dams compared with the other groups at 31 d of age. Prepregnancy and early in utero Zn deficiency affected IgA responses in pups that could not be restored with Zn supplementation during pregnancy. Zn supplementation of ZC dams induced immunosuppressive effects in utero that may also be mediated through milk and persist in the offspring after weaning.

Interactions of malnutrition and immune impairment, with specific reference to immunity against parasites

1. Clinical malnutrition is a heterogenous group of disorders including macronutrient deficiencies leading to body cell mass depletion and micronutrient deficiencies, and these often coexist with infectious and inflammatory processes and environmental problems. 2. There is good evidence that specific micronutrients influence immunity, particularly zinc and vitamin A. Iron may have both beneficial and deleterious effects depending on circumstances. 3. There is surprisingly slender good evidence that immunity to parasites is dependent on macronutrient intake or body composition.

Effect of month of vaccine administration on antibody responses in The Gambia and Pakistan

OBJECTIVE

To explore the relationship between calendar month of administration and antibody (Ab) response to vaccination in subjects from The Gambia and Pakistan, two countries with distinct patterns of seasonality.

METHODS

Three cohorts were investigated: Responses to rabies and pneumococcal vaccine were assessed in 472 children (mean age 8 years, males 53%) from rural Gambia. Responses to tetanus, diphtheria and hepatitis B (HBsAg) were investigated in 138 infants also from The Gambia (birth to 52 weeks of age, males 54%). Responses to rabies and Vi typhoid vaccines were assessed in 257 adults from Lahore, Pakistan (mean age 29.4 years, males 57%).

RESULTS

In Gambian children, significant associations were observed between month of vaccination and Ab response for the pneumococcal and rabies vaccines. As no consistent pattern by month was observed between the responses, it is assumed that different immunomodulatory stimuli or mechanisms were involved. In Pakistani adults, a significant pattern by month of vaccination was observed with both rabies and typhoid vaccine. No monthly influences were observed in the infant study to the tetanus, diphtheria or the HbsAg vaccines.

CONCLUSIONS

Antibody responses to certain specific vaccines are influenced by month of administration. Further research is required to elucidate the precise mechanisms explaining these observations, but a co-stimulatory effect of seasonally variable environmental antigens is a likely cause. Future studies of Ab response to vaccination in countries with a seasonally dependent environment should consider month of vaccination when interpreting study findings.

Severe feed restriction enhances innate immunity but suppresses cellular immunity in chicken lines divergently selected for antibody responses

The main aim of this study was to investigate the effects of different levels of feed restriction (FR) on immune responses of chicken lines divergently selected for high (H) and low (L) antibody responses to SRBC. We hypothesized that severe feed restriction suppresses immune responses and the level of immune suppression differs between birds with different genetic background. Therefore, we tested antibody responses, blood lymphocyte proliferative responses, and production of reactive oxygen intermediates (ROI) by Zymosan A-stimulated blood cells in chicken lines maintained on 3 levels of FR. The H line birds had significantly higher antibody responses, higher ROI production, and lower corticosterone (CORT) levels when compared with the L line birds. Feed restriction induced no significant effect on specific antibody responses to either a T helper 1- (Mycobacterium butyricum) or a T helper 2- (keyhole limpet hemocyanin) type antigen. Feed-restricted birds showed a marked reduction in natural antibodies binding lipoteichoic acid, in vitro lymphocyte proliferation in response to stimulation with concanavalin A, BW gain, and relative lymphoid organ weights compared with the birds fed ad libitum. However, FR birds showed a markedly enhanced ROI production, and plasma CORT levels compared with the birds fed ad libitum. The enhanced ROI production and suppressed lymphocyte proliferation coinciding with enhanced plasma CORT levels suggest stress-mediated immunomodulating effects of FR. A significant treatment by line interaction was found for ROI production; the increase of ROI production was larger in the H line than in the L line under severe FR. The increase in CORT levels was larger in the L line than in the H line under severe FR. Furthermore, the L line gained more BW than the H line under ad libitum conditions. Finally, under severe FR, relative spleen weight was lower in the L line than in the H line. The present findings suggest genetic differences affecting physiological and immunological responses under FR conditions.

Transient environmental exposures on the developing immune system: implications for allergy and asthma

PURPOSE OF REVIEW

Early environmental exposures have been extensively studied as potential causes of the observed increase in allergic disease over time. Transient fetal or neonatal exposures in particular are of interest in that they may occur during critical windows of immune system development. Due to the tremendous complexity of variables in early life, as well as the difficulty in randomizing many interventions, it is very difficult to properly study these exposures. Some progress, however, has been made and some more candidates for study may be emerging. Of particular interest are micronutrients, whose ever-changing use and immunomodulatory capabilities make them prime targets for study.

RECENT FINDINGS

New risk factors for atopic disease have emerged from the pool of early life interventions, such as caesarian section, prolonged labor and infant multivitamin supplementation. Data are emerging regarding micronutrient status and supplementation and their effects on the developing immune system and risk for allergic disease. Clinical trials have yet to demonstrate much causality but, in some cases, it is too early to make any judgments.

SUMMARY

The gold standard of randomized clinical trials has not borne out a number of proposed early-life allergic risk factors, while other trials are too incomplete to draw any conclusions so far. Properly designed studies for other risk factor interventions may still be achievable, provided that there is a proper understanding of the interventions, populations and outcomes.

Pneumococcal conjugate vaccines for preventing vaccine-type invasive pneumococcal disease and pneumonia with consolidation on x-ray in children under two years of age

BACKGROUND

Pneumonia, most commonly caused by Streptococcus pneumoniae (Pnc), is a major cause of morbidity and mortality among young children especially in developing countries. Recently, the prevalence of antibiotic-resistant Pnc has increased worldwide such that the effectiveness of preventive strategies, like the new pneumococcal conjugate vaccines (PCV) on rates of invasive pneumococcal disease (IPD) and pneumonia, needs to be evaluated.

OBJECTIVES

To determine the efficacy of PCV in reducing the incidence of IPD due to vaccine serotypes (VT) and x-ray confirmed pneumonia with consolidation of unspecified etiology in children who received PCV before 12 months of age.

SEARCH STRATEGY

We searched the following databases: the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library, Issue 1 2004), MEDLINE (1990 to March 2004) and EMBASE (1990 to December 2003). Reference list of articles, and books of abstracts of relevant symposia, were hand searched. Researchers in the field were also contacted.

SELECTION CRITERIA

Randomised controlled trials (RCTs) comparing PCV with placebo, or another vaccine, among children below two years with IPD and clinical/radiographic pneumonia as outcomes.

DATA COLLECTION AND ANALYSIS

Two reviewers independently identified eligible studies, assessed trial quality, and extracted data. Differences were resolved by discussion. The inverse variance method was used to pool effect sizes.

MAIN RESULTS

We identified four trials assessing the efficacy of PCV in reducing the incidence of IPD, two on x-ray confirmed pneumonia as outcome, and one on clinical pneumonia, with or without x-ray confirmation. Results from pooling HIV-1 negative children from the South African study with the other studies were as follows: the pooled vaccine efficacy (VE) for vaccine-type IPD was 88% (95% confidence interval (CI) 73% to 94%; fixed effect and random effects models), the effect measure was statistically significant (p <0.00001) and there was no heterogeneity (p = 0.77I2 0%); the pooled VE for all-serotype IPD was 66% (95% CI 46% to 79%; fixed effect model), the effect measure was statistically significant (p <0.00001) and there was no statistical heterogeneity (p = 0.09, I2 51%); the pooled VE for x-ray confirmed pneumonia was 22% (95% CI 11% to 31%; both fixed effect and random effects models) and there was no statistical heterogeneity (p = 0.80, I2 0%). Analyses that included all the children in the South African study (HIV-1 negative and HIV-1 positive children) and pooled with data from the other studies gave very similar results.

REVIEWERS' CONCLUSIONS

PCV is effective in reducing the incidence of IPD from all serotypes but exerts a greater effect in reducing VT IPD. Although PCV is also effective in reducing the incidence of x-ray confirmed pneumonia, there are still uncertainties about the definition of this outcome. Additional randomised controlled trials are currently in progress.