Cost-effectiveness analysis of maternal immunisation against group B Streptococcus (GBS) disease: A modelling study

Maternal Immunizations: Past, Present, and Future

Maternal vaccines during pregnancy offer crucial protection against infections for both the pregnant person and their newborn. Vaccines against influenza, pertussis, coronavirus disease 2019, and respiratory syncytial virus are routinely recommended by the Centers for Disease Control and Prevention to safeguard pregnant women and their infants from potentially severe complications. Administering these vaccines during pregnancy helps transfer protective antibodies from the mother to the baby, enhancing immunity during the vulnerable early months of life. Extensive research supports the safety and efficacy of maternal vaccines, with numerous studies demonstrating their protective benefits for both pregnant people and newborns.

GBS vaccines in the UK: a round table discussion

Background

Group B streptococcus (GBS) remains a leading cause of infant sepsis, meningitis and death despite intrapartum antibiotic prophylaxis. A vaccine is urgently required, and two candidates are in advanced clinical trials. For successful GBS vaccine implementation, especially if a vaccine is licensed based on an immunological threshold, there must be cross-sector engagement, effective advocacy, robust plans for phase IV studies and equitable access.

Meeting

A round-table discussion, held at St George's University of London, reviewed the current position of GBS vaccines in the UK context, focusing on phase IV plans, convening a diverse group of stakeholders from across the UK, with a role in GBS vaccine licensure, advocacy, implementation or effectiveness evaluation.Presentations outlined the latest UK epidemiology, noting the rising infant invasive GBS (iGBS) infection rates from 1996 to 2021 for both early and late onset disease, with the highest disease rates in Black infants (1.1/1000 livebirths vs white infants (0.81/1000 livebirths). Potential coverage of the candidate vaccines was high (>95%). Regulatory input suggested that EU regulators would consider waiving the need for a pre-licensure efficacy study if a putative correlate of protection could be adequately justified. Phase IV study methodologies for a GBS vaccine were considered, largely based on previous UK maternal vaccine assessments, such as a nationwide cohort study design using a vaccine register and a maternal services dataset. Other strategies were also discussed such as a cluster or stepped-wedge randomised trial to evaluate implementation outcomes. Opportunities for advocacy, education and engagement with additional key partners were discussed and identified.

Conclusions

With an approved GBS vaccine a near possibility, planning of phase IV studies and identification of critical barriers to implementation are urgently needed. Cross-sector engagement is essential and will facilitate a successful pathway.

Long-term healthcare utilisation, costs and quality of life after invasive group B Streptococcus disease: a cohort study in five low-income and middle-income countries

INTRODUCTION

There are no published data on the long-term impact of invasive group B Streptococcus disease (iGBS) on economic costs or health-related quality of life (HRQoL) in low-income and middle-income countries. We assessed the impact of iGBS on healthcare utilisation, costs and HRQoL in Argentina, India, Kenya, Mozambique and South Africa.

METHODS

Inpatient and outpatient visits, out-of-pocket (OOP) healthcare payments in the 12 months before study enrolment, and health-state utility of children and caregivers (using the EuroQol 5-Dimensions-3-Level) were collected from iGBS survivors and an unexposed cohort matched on site, age at recruitment and sex. We used logistic or Poisson regression for analysing healthcare utilisation and zero-inflated gamma regression models for family and health system costs. For HRQoL, we used a zero-inflated beta model of disutility pooled data.

RESULTS

161 iGBS-exposed and 439 unexposed children and young adults (age 1-20) were included in the analysis. Compared with unexposed participants, iGBS was associated with increased odds of any healthcare utilisation in India (adjusted OR 11.2, 95% CI 2.9 to 43.1) and Mozambique (6.8, 95% CI 2.2 to 21.1) and more frequent healthcare visits (adjusted incidence rate ratio (IRR) for India 1.7 (95% CI 1.4 to 2.2) and for Mozambique 6.0 (95% CI 3.2 to 11.2)). iGBS was also associated with more frequent days in inpatient care in India (adjusted IRR 4.0 (95% CI 2.3 to 6.8) and Kenya 6.4 (95% CI 2.9 to 14.3)). OOP payments were higher in the iGBS cohort in India (adjusted mean: Int$682.22 (95% CI Int$364.28 to Int$1000.16) vs Int$133.95 (95% CI Int$72.83 to Int$195.06)) and Argentina (Int$244.86 (95% CI Int$47.38 to Int$442.33) vs Int$52.38 (95% CI Int$-1.39 to Int$106.1)). For all remaining sites, differences were in the same direction but not statistically significant for almost all outcomes. Health-state disutility was higher in iGBS survivors (0.08, 0.04-0.13 vs 0.06, 0.02-0.10).

CONCLUSION

The iGBS health and economic burden may persist for years after acute disease. Larger studies are needed for more robust estimates to inform the cost-effectiveness of iGBS prevention.

Vaccine value profile for Group B streptococcus

Group B streptococcus (GBS) is a major global cause of neonatal meningitis, sepsis and pneumonia, with an estimated 91,000 infant deaths per year and an additional 46,000 stillbirths. GBS infection in pregnancy is also associated with adverse maternal outcomes and preterm births. As such, the World Health Organization (WHO) prioritised the development of a GBS vaccine suitable for use in pregnant women and use in LMICs, where the burden of disease is highest. Several GBS vaccines are in clinical development. The WHO Defeating Meningitis by 2030 has set a target of 2026 for vaccine licensure. This 'Vaccine Value Profile' (VVP) for GBS is intended to provide a high-level, holistic assessment of the information and data that are currently available to inform the potential public health, economic and societal value of pipeline vaccines and vaccine-like products. This VVP was developed by a working group of subject matter experts from academia, non-profit organizations, public private partnerships and multi-lateral organizations, and in collaboration with stakeholders from the WHO regions of AFR, AMR, EUR, WPR. All contributors have extensive expertise on various elements of the GBS VVP and collectively aimed to identify current research and knowledge gaps. The VVP was developed using only existing and publicly available information.

Cost-effectiveness analysis of maternal vaccination against Group B streptococcus in Japan

Background

Group B Streptococcus (GBS) is a leading pathogen causing life-threatening bacterial infections in neonates (early- or late-onset) and infants, and is associated with preterm and stillbirth. Japan introduced national guidelines to reduce early-onset neonatal GBS disease, with universal prenatal screening and intrapartum antimicrobial prophylaxis (IAP). However, screening/IAP does not prevent GBS associated late-onset disease, preterm or stillbirth. Maternal GBS vaccines in development are targeted at infant GBS disease but may provide benefit across perinatal outcomes. We aimed to assess cost-effectiveness of a future maternal GBS vaccine, for a base case prevention of infant GBS disease in combination with screening/IAP compared to screening/IAP alone.

Methods

We used a decision tree model to estimate cases of infant GBS disease, deaths, and neuro-developmental impairment (NDI), GBS-related stillbirths, and the associated costs and loss in Quality-Adjusted Life Years (QALYs). We calculate the threshold price at which a vaccine would be cost-effective assuming a cost-effectiveness threshold of ¥5 million/QALY. We explored the potential benefit of a maternal GBS vaccine that also prevents preterm birth in a scenario analysis.

Results

Maternal GBS vaccination in Japan could prevent an additional 142 infant GBS cases annually, including 5 deaths and 21 cases of NDI, and 13 stillbirths compared to screening/IAP alone. The incremental cost-effectiveness ratio (ICER) was ¥3.78 million/QALY with a vaccine cost of ¥5,000/dose. If the QALY lost for stillbirth is included, the ICER is reduced to ¥1.78 million/QALY. Median threshold vaccine price was ¥6,900 per dose (95 % uncertainty interval ¥5,100 to ¥9,200 per dose). If maternal GBS vaccination also prevented half of GBS-associated preterm, the ICER would be reduced to ¥1.88 million/QALY.

Conclusions

An effective maternal GBS vaccine is likely to be considered cost-effective in Japan at a price of ¥5,000/dose. Effectiveness against other adverse perinatal outcomes would increase health benefits and cost-effectiveness.

Neonatal Group B Streptococcal Infection in Australia: A Case-control Study

BACKGROUND

To determine maternal and neonatal risk factors for, and incidence of, neonatal early-onset group B streptococcus (EOGBS) and late-onset (LOGBS) infection in South Australia (SA) and the Northern Territory (NT).

METHODS

A case-control study with 2:1 matched controls to cases. The study included tertiary hospitals in South Australia and the Northern Territory, Australia. Retrospective data were collected from a 16-year epoch (2000-2015).

RESULTS

Of a total of 188 clinically suspected or confirmed cases, 139 were confirmed, of which 56.1% (n = 78) were EOGBS and 43.9% (n = 61) were LOGBS. The incidence of clinically suspected and confirmed cases of EOGBS was 0.26/1000 live births in SA and 0.73/1000 live births in the NT, and the incidence of confirmed cases was 0.19/1000 for SA and 0.36/1000 for the NT. The incidence of clinically suspected or confirmed LOGBS was 0.18/1000 live births in SA and 0.16/1000 for the NT. The majority of infants with GBS presented with sepsis, pneumonia, or meningitis. Developmental delay was the most commonly recorded long-term complication at 1 year old. Risk factors for EOGBS included maternal GBS carriage, previous fetal death, identifying as Aboriginal and/or Torres Strait Islander, and maternal fever in labor/chorioamnionitis.

CONCLUSIONS

GBS remains a leading cause of neonatal morbidity and mortality. Adding previous fetal death to GBS screening guidelines would improve GBS prevention. The introduction of maternal GBS vaccination programs should be guided by country-specific disease epidemiology.

Maternity care provider acceptance of a future Group B Streptococcus vaccine - A qualitative study in three countries

INTRODUCTION

There are vaccines in clinical trials that target the bacterium Group B Streptococcus (GBS). When approved, GBS vaccines will be intended for administration to pregnant women to prevent infection in their infants. The success of any vaccine will depend on its' uptake in the population. Experience with prior maternal vaccines, e.g. influenza, Tdap and COVID-19 vaccines, teaches us that acceptance of vaccines, especially if novel, is challenging for pregnant women, and that provider recommendation is a key driver of vaccine uptake.

METHODS

This study investigated attitudes of maternity care providers towards the introduction of a GBS vaccine in three countries (the United States (US), Ireland, and the Dominican Republic (DR)) with different GBS prevalence and prevention practices. Semi-structured interviews with maternity care providers were transcribed and coded for themes. The constant comparative method, and inductive theory building were used to develop conclusions.

RESULTS

Thirty-eight obstetricians, 18 general practitioners and 14 midwives participated. There was variability in provider attitudes towards a hypothetical GBS vaccine. Responses ranged from enthusiasm to doubts over the need for a vaccine. Attitudes were influenced by perceived additional benefits of a vaccine over current strategy and confidence in the safety of vaccines during pregnancy. Knowledge, experience and approaches to GBS prevention differed geographically and according to provider type, and influenced how participants assessed the risks and benefits of a GBS vaccine.

CONCLUSION

Maternity care providers are engaged in the topic of GBS management and there is opportunity to leverage attitudes and beliefs that will support a strong recommendation for a GBS vaccine. However, knowledge of GBS, and of the limitations of current prevention strategies vary among providers in different regions, and between different provider types. Targeted educational efforts with antenatal providers should focus on highlighting safety data the potential benefits of vaccination over current strategies.

Association of infant Rib and Alp1 surface protein N-terminal domain immunoglobulin G and invasive Group B Streptococcal disease in young infants

BACKGROUND

Vaccine development for Group B Streptococcus (GBS), a common cause of invasive disease in early-infancy and adverse pregnancy outcomes, include exploring widely-expressed GBS surface proteins as vaccine epitopes. We investigated the association between natural infant serum IgG against the RibN and Alp1N domains and risk of invasive GBS disease caused by isolates expressing these proteins.

METHODS

We analyzed maternal and infant serum samples from GBS disease cases and infants born to GBS-colonized women controls. Bayesian modelling was used to calculate the GBS homotypic IgG concentration associated with risk reduction of invasive disease in the infant.

RESULTS

PCR-based typing of 85 GBS invasive isolates showed 46 and 24 possessing the gene for Rib and Alp1, respectively. These were matched to 46 and 36 infant controls whose mothers were colonized with GBS expressing Rib and Alp1, respectively. RibN IgG geometric mean concentrations (GMC) were lower in cases than controls among infants (0.01; 95 %CI: 0.01-0.02 vs 0.04; 95 %CI: 0.03-0.06; p < 0.001), no significant difference was found between maternal RibN IgG GMC in cases compared to controls. Alp1N IgG GMC was also lower in infant cases (0.02; 95 %CI: 0.01-0.03) than controls (0.05; 95 %CI: 0.04-0.07; p < 0.001); albeit not so in mothers. An infant IgG threshold ≥ 0.428 and ≥ 0.112 µg/mL was associated with 90 % risk reduction of invasive GBS disease due to Rib and Alp1 expressing strains, respectively.

DISCUSSION

Lower serum RibN and Alp1N IgG GMC were evident in infants with invasive GBS disease compared with controls born to women colonized with GBS expressing the homotypic protein. These data support the evaluation of Alp family proteins as potential vaccine candidates against invasive GBS disease.

Maternal immunisation against Group B Streptococcus: A global analysis of health impact and cost-effectiveness

BACKGROUND

Group B Streptococcus (GBS) can cause invasive disease (iGBS) in young infants, typically presenting as sepsis or meningitis, and is also associated with stillbirth and preterm birth. GBS vaccines are under development, but their potential health impact and cost-effectiveness have not been assessed globally.

METHODS AND FINDINGS

We assessed the health impact and value (using net monetary benefit (NMB), which measures both health and economic effects of vaccination into monetary units) of GBS maternal vaccination in an annual cohort of 140 million pregnant women across 183 countries in 2020. Our analysis uses a decision tree model, incorporating risks of GBS-related health outcomes from an existing Bayesian disease burden model. We extrapolated country-specific GBS-related healthcare costs using data from a previous systematic review and calculated quality-adjusted life years (QALYs) lost due to infant mortality and long-term disability. We assumed 80% vaccine efficacy against iGBS and stillbirth, following the WHO Preferred Product Characteristics, and coverage based on the proportion of pregnant women receiving at least 4 antenatal visits. One dose was assumed to cost $50 in high-income countries, $15 in upper-middle income countries, and $3.50 in low-/lower-middle-income countries. We estimated NMB using alternative normative assumptions that may be adopted by policymakers. Vaccinating pregnant women could avert 127,000 (95% uncertainty range 63,300 to 248,000) early-onset and 87,300 (38,100 to 209,000) late-onset infant iGBS cases, 31,100 deaths (14,400 to 66,400), 17,900 (6,380 to 49,900) cases of moderate and severe neurodevelopmental impairment, and 23,000 (10,000 to 56,400) stillbirths. A vaccine effective against GBS-associated prematurity might also avert 185,000 (13,500 to 407,000) preterm births. Globally, a 1-dose vaccine programme could cost $1.7 billion but save $385 million in healthcare costs. Estimated global NMB ranged from $1.1 billion ($-0.2 to 3.8 billion) under the least favourable normative assumptions to $17 billion ($9.1 to 31 billion) under the most favourable normative assumptions. The main limitation of our analysis was the scarcity of data to inform some of the model parameters such as those governing health-related quality of life and long-term costs from disability, and how these parameters may vary across country contexts.

CONCLUSIONS

In this study, we found that maternal GBS vaccination could have a large impact on infant morbidity and mortality. Globally, a GBS maternal vaccine at reasonable prices is likely to be a cost-effective intervention.

Group B Streptococcus and Pregnancy: Critical Concepts and Management Nuances

Importance

Group B Streptococcus (GBS) is a common pathogen with an effective treatment. However, it remains a significant cause of neonatal sepsis, morbidity, and mortality. The screening and management of this infection are some of the first concepts learned during medical training in obstetrics. However, effective screening and evidence-based management of GBS are nuanced with many critical caveats.

Objective

The objectives of this review are to discuss the essential aspects of GBS screening and management and to highlight recent changes to recommendations and guidelines.

Evidence Acquisition

Original research articles, review articles, and guidelines on GBS were reviewed.

Results

The following recommendations are based on review of the evidence and professional society guidelines. Screening for GBS should occur between 36 weeks and the end of the 37th week. The culture swab should go 2 cm into the vagina and 1 cm into the anus. Patients can perform their own swabs as well. Penicillin allergy testing has been shown to be safe in pregnancy. Patients with GBS in the urine should be treated at term with antibiotic prophylaxis, independent of the colony count of the culture. Patients who are GBS-positive with preterm and prelabor rupture of membranes after 34 weeks are not candidates for expectant management, as this population has higher rates of neonatal infectious complications. Patients with a history of GBS colonization in prior pregnancy who are GBS-unknown in this current pregnancy and present with labor should receive intrapartum prophylaxis. Work on the GBS vaccine continues.

Conclusions

Although all of the efforts and focus on neonatal early-onset GBS infection have led to lower rates of disease, GBS still remains a major cause of neonatal morbidity and mortality requiring continued vigilance from obstetric providers.

Estimation of invasive Group B Streptococcus disease risk in young infants from case-control serological studies

Background

Group B Streptococcus (GBS) infections are a major cause of invasive disease (IGbsD) in young infants and cause miscarriage and stillbirths. Immunization of pregnant women against GBS in addition to intrapartum antibiotic prophylaxis could prevent disease. Establishing accurate serological markers of protection against IGbsD could enable use of efficient clinical trial designs for vaccine development and licensure, without needing to undertake efficacy trials in prohibitively large number of mother-infant dyads. The association of maternal naturally acquired serotype-specific anti-capsular antibodies (IgG) against serotype-specific IGbsD in their infants has been studied in case-control studies. The statistical models used so far to estimate IGbsD risk from these case-control studies assumed that the antibody concentrations measured sharing the same disease status are sampled from the same population, not allowing for differences between mothers colonised by GBS and mothers also potentially infected (e.g urinary tract infection or chorioamnionitis) by GBS during pregnancy. This distinction is relevant as infants born from infected mothers with occult medical illness may be exposed to GBS prior to the mother developing antibodies measured in maternal or infant sera.

Methods

Unsupervised mixture model averaging (MMA) is proposed and applied here to accurately estimate infant IGbsD risk from case-control study data in presence or absence of antibody concentration subgroups potentially associated to maternal GBS carriage or infection. MMA estimators are compared to non-parametric disease risk estimators in simulation studies and by analysis of two published GBS case-control studies.

Results

MMA provides more accurate relative risk estimates under a broad range of data simulation scenarios and more accurate absolute disease risk estimates when the proportion of IGbsD cases with high antibody levels is not ignorable. MMA estimates of the relative and absolute disease risk curves are more amenable to clinical interpretation compared to non-parametric estimates with no detectable overfitting of the data. Antibody concentration thresholds predictive of protection from infant IGbsD estimated by MMA from maternal and infant sera are consistent with non-parametric estimates.

Conclusions

MMA is a flexible and robust method for design, accurate analysis and clinical interpretation of case-control studies estimating relative and absolute IGbsD risk from antibody concentrations measured at or after birth.

Immediate birth for women between 34 and 37 weeks of gestation with prolonged preterm prelabour rupture of membranes and detection of vaginal or urine group B streptococcus: an economic evaluation

Objective

What are the costs, benefits and harms of immediate birth compared with expectant management in women with prolonged preterm prelabour rupture of membranes (PPROM) at 34⁺⁰–36⁺⁶ weeks of gestation and detection of vaginal or urine group B streptococcus (GBS)?

Design

Mathematical decision model comprising three independent decision trees.

Setting

UK National Health Service (NHS) and personal social services perspective.

Population

Women testing positive for GBS with PPROM at 34⁺⁰–36⁺⁶ weeks of gestation.

Methods

The model estimates lifetime costs and quality‐adjusted life years (QALYs) using evidence from randomised trials, UK NHS data sources and further observational studies. Simulated events include neonatal infections, morbidity associated with preterm birth and consequences of caesarean birth. Deterministic and probabilistic sensitivity analyses (PSAs) were performed.

Main outcome measures

QALYs, costs and incremental cost‐effectiveness ratio (ICER).

Results

In this population, immediate birth dominates expectant management: it is more effective (average lifetime QALYs, 24.705 versus 24.371) and it is cheaper (average lifetime costs, £14,372 versus £19,311). In one‐way sensitivity analysis, results are robust to all but the odds ratio estimating the relative effect on incidence of infections. Threshold analysis shows that the odds of infection only need to be >1.5% with expectant management for the benefit of avoiding infections to outweigh the disadvantages of immediate birth. In PSA, immediate birth is the preferred option in >80% of simulations.

Conclusions

Neonatal GBS infections are expensive to treat and may result in substantial adverse health consequences. Therefore, immediate birth, which is associated with a reduced risk of neonatal infection compared with expectant management, is expected to generate better health outcomes and decreased lifetime costs.

Tweetable abstract

For women with preterm prelabour rupture of membranes and group B streptococcus in vaginal or urine samples, immediate birth is associated with improved health in their babies and reduced costs, compared with expectant management.

For women with preterm prelabour rupture of membranes and group B streptococcus in vaginal or urine samples, immediate birth is associated with improved health in their babies and reduced costs, compared with expectant management.

Invasive Group B Streptococcus Infections in Adults, England, 2015-2016

During 2015–2016, a total of 3,156 episodes of invasive group B Streptococcus (iGBS) infection in adults (>15 years of age) were recorded in England, corresponding to an annual incidence of 3.48/100,000 population. iGBS incidence was highest in older patients and women of childbearing age. The 493 pregnancy-related iGBS episodes correspond to a rate of 1.34/10,000 live births. In adults up to 60–69 years of age and in pregnant women, iGBS incidence increased with higher levels of socioeconomic deprivation. Hospital admissions associated with iGBS were predominantly emergency admissions (73% [2,260/3,099]); only 7% of nonpregnancy iGBS diagnoses were made >48 hours after admission. Underlying conditions were highly prevalent in nonpregnant adult case-patients, including cardiovascular (57%), lung (43%), and kidney (45%) disease and diabetes (40%). Post-iGBS episode 30-day and 12-month all-cause mortality rates in nonpregnant adults were 12% and 24%, respectively. No pregnancy-related iGBS deaths were identified.

Cost-effectiveness of maternal immunization against neonatal invasive Group B Streptococcus in the Netherlands

BACKGROUND

Neonatal invasive Group B Streptococcus (GBS) infection causes considerable disease burden in the Netherlands. Intrapartum antibiotic prophylaxis (IAP) prevents early-onset disease (EOD), but has no effect on late-onset disease (LOD). A potential maternal GBS vaccine could prevent both EOD and LOD by conferring immunity in neonates.

OBJECTIVE

Explore under which circumstances maternal vaccination against GBS would be cost-effective as an addition to, or replacement for the current risk factor-based IAP prevention strategy in the Netherlands.

METHODS

We assessed the maximum cost-effective price per dose of a trivalent (serotypes Ia, Ib, and III) and hexavalent (additional serotypes II, IV, and V) GBS vaccine in addition to, or as a replacement for IAP. To project the prevented costs and disease burden, a decision tree model was developed to reflect neonatal GBS disease and long-term health outcomes among a cohort based on 169,836 live births in the Netherlands in 2017.

RESULTS

Under base-case conditions, maternal immunization with a trivalent vaccine would gain 186 QALYs and prevent more than €3.1 million in health care costs when implemented in addition to IAP. Immunization implemented as a replacement for IAP would gain 88 QALYs compared to the current prevention strategy, prevent €1.5 million in health care costs, and avoid potentially ~ 30,000 IAP administrations. The base-case results correspond to a maximum price of €58 per dose (vaccine + administration costs; using a threshold of €20,000/QALY). Expanding the serotype coverage to a hexavalent vaccine would only have a limited additional impact on the cost-effectiveness in the Netherlands.

CONCLUSIONS

A maternal GBS vaccine could be cost-effective when implemented in addition to the current risk factor-based IAP prevention strategy in the Netherlands. Discontinuation of IAP would save costs and prevent antibiotic use, however, is projected to lead to a lower health gain compared to vaccination in addition to IAP.

Differences in maternal group B Streptococcus screening rates in Latin American countries

OBJECTIVE

To determine rates and results of maternal Group B streptococcus (GBS) screening during pregnancy and identify sociodemographic characteristics associated with GBS screening in Latin American countries.

BACKGROUND

GBS is a primary cause of morbidity and mortality in neonates and is prevented by screening pregnant women for GBS before delivery and intrapartum antibiotic treatment. Yet, data regarding national GBS screening practices and the epidemiology of maternal GBS colonization in Latin America are limited.

METHODS

We conducted a retrospective observational study using de-identified records of pregnant women in six Latin American countries from a regional database. 460,328 collected from January 1, 2009 through December 31, 2012 met study criteria and were included. Maternal screening rates for GBS were determined, association of demographic variables (ethnicity, age, education level, and civil status) with maternal GBS screening was determined using logistic regression, odds ratios were calculated comparing incidence of adverse neonatal outcomes (sepsis, pneumonia, and meningitis) between countries with high and low rates of GBS screening, maternal GBS colonization prevalence was determined by year and association of demographic variables with maternal GBS colonization was determined using logistic regression.

RESULTS

Maternal GBS screening was less than 15% in each country, except Uruguay which screened greater than 65% of women. The final regression model examining maternal screening rates and demographic variables included the covariates ethnicity, maternal age group, education level and civil status. Countries with lower rates of maternal GBS screening had increased odds of neonatal sepsis [OR 23.3; 95% CI (15.2-35.9)] and pneumonia [OR 19.9; 95% CI (12.1-32.6)]. In Uruguay, GBS prevalence over the study period was 18.5%. Black women, older women and women without a primary education had higher rates of GBS colonization (21.3%, 20.4% and 21.9% respectively).

CONCLUSIONS

Our study highlights the need for national policy and investments to increase maternal GBS screening and better understand the prevalence of maternal GBS colonization in Latin America. Further research on the burden of neonatal GBS disease within Latin America is needed to inform the introduction of a maternal GBS vaccine, when available.

A review of the costs of delivering maternal immunisation during pregnancy

Background

Routine maternal immunisation against influenza and pertussis are recommended by the WHO to protect mother and child, and new vaccines are under development. Introducing maternal vaccines into national programmes requires an understanding of vaccine delivery costs – particularly in low resource settings.

Methods

We searched Medline, Embase, Econlit, and Global Health for studies reporting costs of delivering vaccination during pregnancy but excluded studies that did not separate the vaccine purchase price. Extracted costs were inflated and converted to 2018 US dollars.

Results

Sixteen studies were included, of which two used primary data to estimate vaccine delivery costs. Costs per dose ranged from $0.55 to $0.64 in low-income countries, from $1.25 to $6.55 for middle-income countries, and from $5.76 to $39.87 in high-income countries.

Conclusions

More research is needed on the costs of delivering maternal immunisation during pregnancy, and of integrating vaccine delivery into existing programmes of antenatal care especially in low and middle-income countries.

Potential cost-effectiveness of a maternal Group B streptococcal vaccine in The Gambia

OBJECTIVE

To estimate neonatal health benefits and healthcare provider costs of a theoretical Group B streptococcal (GBS) hexavalent maternal vaccination programme in The Gambia, a low-income setting in West Africa.

METHODS

A static decision analytic cost-effectiveness model was developed from the healthcare provider perspective. Demographic data and acute care costs were available from studies in The Gambia undertaken in 2012-2015. Further model parameters were taken from United Nations and World Health Organisation sources, supplemented by data from a global systematic review of GBS and literature searches. As vaccine efficacy is not known, we simulated vaccine efficacy estimates of 50-90%. Costs are reported in US dollars. Cost-effectiveness thresholds of one (US$473, very cost effective) and three (US$1420, cost effective) times Gambian GDP were used.

RESULTS

Vaccination with a hexavalent vaccine would avert 24 GBS disease cases (55%) and 768 disability adjusted life years compared to current standard of care (no interventions to prevent GBS disease). At vaccine efficacy of 70%, the programme is cost-effective at a maximum vaccine price per dose of 12 US$ (2016 US$), and very cost-effective at a maximum of $3/dose. The total costs of vaccination at $12 is $1,056,962 for one annual cohort of Gambian pregnant women. One-way sensitivity analysis showed that GBS incidence was the most influential parameter on the cost effectiveness ratio.

CONCLUSION

The introduction of a hexavalent vaccine would considerably reduce the current burden of GBS disease in The Gambia but to be cost-effective, the vaccine price per dose would need to be $12/dose or less.

Mucosal Vaccination with Lactococcus lactis-Secreting Surface Immunological Protein Induces Humoral and Cellular Immune Protection against Group B Streptococcus in a Murine Model

Group B Streptococcus (GBS) is the primary etiological agent of sepsis and meningitis in newborns and is associated with premature birth and stillbirth. The development of a licensed vaccine is one of the pending challenges for the World Health Organization. Previously, we showed that oral immunization with surface immune protein (SIP) decreases vaginal colonization of GBS and generates functional opsonizing antibodies, which was determined by opsonophagocytic assays (OPA) in vitro. We also showed that the protein has an adjuvant vaccine profile. Therefore, an oral vaccine based on SIP may be an attractive alternative to employ in the development of new vaccines against GBS. Lactococcus lactis is a highlighted oral vaccine probiotic inducer of the mucosal immune response. This bacterium could serve as an antigen-delivering vehicle for the development of an edible vaccine and has been used in clinical trials. In this study, we showed that an oral vaccine with a recombinant L. lactis strain secreting SIP from GBS (rL. lactis-SIP) can induce protective humoral and cellular immunity in an experimental model of GBS vaginal colonization in C57BL/6 mice. Mice immunized with rL. lactis-SIP were protected against clinical symptoms and bacterial colonization after GBS vaginal colonization. Our rL. lactis-SIP vaccine also induces an increase of immunoglobulin G (IgG) and immunoglobulin A (IgA) specifically against SIP. The adoptive transfer of serum from vaccinated mice to naïve mice generated protection against GBS vaginal colonization. Moreover, the rL.lactis-SIP strain induces the activation of SIP-specific T cells, which could decrease GBS vaginal colonization and generate protective antibodies when transferred to other mice. Our experimental observations strongly support the notion that rL. lactis-SIP induces protective humoral and cellular immunity and could be considered as a novel alternative in the development of vaccines for GBS.

Group B Streptococcus: Trials and Tribulations

Group B Streptococcus (GBS) is estimated to have caused 319,000 cases of neonatal disease resulting in 90,000 infant deaths globally in 2015. It is also associated with maternal sepsis, preterm births, stillbirths and neonatal encephalopathy. There is a significant burden of neurologic impairment among survivors of infant GBS disease. Intrapartum antibiotic prophylaxis strategies have reduced the incidence of newborn early-onset GBS (occurring days 0-6) in some settings, but they are not feasible in many low and middle-income countries. A maternal vaccine given to pregnant women to stimulate passive transplacental transfer of protective antibodies has the potential to reduce maternal disease, adverse pregnancy outcomes and newborn disease. Phase I and II vaccine studies are occurring, but conducting phase III efficacy studies of a GBS vaccine candidate would require very large numbers due to the relatively low incidence of invasive GBS disease. It has therefore been proposed that alternative pathways to vaccine licensure should be explored, for example, through use of a regulatory approved correlate of protection and safety evaluation in mothers, fetuses and infants. These studies would then be followed-up with post-licensure phase IV studies in which vaccine effectiveness is evaluated.