Safety of a killed oral cholera vaccine (Shanchol) in pregnant women in Malawi: an observational cohort study

Defining and reporting adverse events of special interest in comparative maternal vaccine studies: a systematic review

Introduction

The GAIA (Global Alignment on Immunisation Safety Assessment in Pregnancy) consortium was established in 2014 with the aim of creating a standardised, globally coordinated approach to monitoring the safety of vaccines administered in pregnancy. The consortium developed twenty-six standardised definitions for classifying obstetric and infant adverse events. This systematic review sought to evaluate the current state of adverse event reporting in maternal vaccine trials following the publication of the case definitions by GAIA, and the extent to which these case definitions have been adopted in maternal vaccine safety research.

Methods

A comprehensive search of published literature was undertaken to identify maternal vaccine research studies. PubMed, EMBASE, Web of Science, and Cochrane were searched using a combination of MeSH terms and keyword searches to identify observational or interventional studies that examined vaccine safety in pregnant women with a comparator group. A two-reviewer screening process was undertaken, and a narrative synthesis of the results presented.

Results

14,737 titles were identified from database searches, 435 titles were selected as potentially relevant, 256 were excluded, the remaining 116 papers were included. Influenza vaccine was the most studied (25.0%), followed by TDaP (20.7%) and SARS-CoV-2 (12.9%).Ninety-one studies (78.4%) were conducted in high-income settings. Forty-eight (41.4%) utilised electronic health-records. The majority focused on reporting adverse events of special interest (AESI) in pregnancy (65.0%) alone or in addition to reactogenicity (27.6%). The most frequently reported AESI were preterm birth, small for gestational age and hypertensive disorders. Fewer than 10 studies reported use of GAIA definitions. Gestational age assessment was poorly described; of 39 studies reporting stillbirths 30.8% provided no description of the gestational age threshold.

Conclusions

Low-income settings remain under-represented in comparative maternal vaccine safety research. There has been poor uptake of GAIA case definitions. A lack of harmonisation and standardisation persists limiting comparability of the generated safety data.

Vibrio cholerae virulence and its suppression through the quorum-sensing system

Vibrio cholerae is a cholera-causing pathogen known to instigate severe contagious diarrhea that affects millions globally. Survival of vibrios depend on a combination of multicellular responses and adapt to changes that prevail in the environment. This process is achieved through a strong communication at the cellular level, the process has been recognized as quorum sensing (QS). The severity of infection is highly dependent on the QS of vibrios in the gut milieu. The quorum may exist in a low/high cell density (LCD/HCD) state to exert a positive or negative response to control the regulatory pathogenic networks. The impact of this regulation reflects on the transition of pathogenic V. cholerae from the environment to infect humans and cause outbreaks or epidemics of cholera. In this context, the review portrays various regulatory processes and associated virulent pathways, which maneuver and control LCD and HCD states for their survival in the host. Although several treatment options are existing, promotion of therapeutics by exploiting the virulence network may potentiate ineffective antibiotics to manage cholera. In addition, this approach is also useful in resource-limited settings, where the accessibility to antibiotics or conventional therapeutic options is limited.

Cholera: An Overview with Reference to the Syrian Outbreak

Cholera is an acute type of diarrheal disease caused by intestinal infection with the toxin-producing bacteria Vibrio cholerae. The disease is still endemic in almost 69 countries, accounting for around 2.86 million cases and 95,000 deaths annually. Cholera is associated with poor infrastructure, and lack of access to sanitation and clean drinking water. The current cholera outbreak in Syria is associated with more than 10 years of conflict, which has devastated infrastructures and health services. There were 132,782 suspected cases reported between August 25, 2022 and May 20, 2023 in all 14 governorates, including 104 associated deaths. The recent earthquake in the region has complicated the situation, with an increase in cholera cases, and hindrance to a response to the disease. Climate change has driven a number of large cholera outbreaks around the world this year. The World Health Organization prequalifies three oral cholera vaccines. Cholera treatment mainly depends on rehydration, with the use of antibiotics in more severe infections. This review gives an overview of cholera bacteriology, pathogenesis, epidemiology, clinical manifestations, diagnosis, management, and prevention in light of global climate change and the ongoing outbreak in Syria, which poses a significant public health threat that requires urgent attention.

Cholera Infection Risks and Cholera Vaccine Safety in Pregnancy

Introduction

Discuss the impact of cholera infection on pregnant women, fetus, and neonates and review the safety of cholera vaccines in pregnancy.

Methods

This study was carried out as a narrative review during November 2022. A thorough literature review was conducted on the following databases: PubMed, Scopus, SciELO, CINAHL, Web of Science, and ScienceDirect. The following parameters were assessed from the included studies: type of cholera vaccine, cholera symptoms, cholera treatment, effect of cholera on pregnancy, effect of cholera treatment on pregnancy, effect of cholera vaccine on pregnancy, risk factors for fetuses and neonates, and prevention of cholera. The authors independently extracted data from the 24 included studies.

Results

Cholera infection is a serious threat on pregnancy as it could lead to increased stillbirths and neonatal death. Fetal death was shown to occur mainly in the third trimester as most of the pregnant women infected with cholera had spontaneous abortions even after controlling for other confounding variables such as maternal age, dehydration level, and vomiting. Neonatal death was attributed mainly to congenital malformations and low Apgar scores with no improvements. Besides, cholera vaccines have shown to be safe in pregnancy and have proven to lower fetal and neonatal malformations among vaccinated compared to nonvaccinated pregnant women.

Conclusion

This narrative summarizes the different complications due to cholera infection in pregnancy. It also reviews the safety of cholera vaccine administration in pregnant women.

Maternal vaccination: a review of current evidence and recommendations

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

Meeting report: CEPI consultation on accelerating access to novel vaccines against emerging infectious diseases for pregnant and lactating women, London, 12-13 February 2020

Infectious diseases may cause serious morbidity and mortality in pregnant women, their foetuses, and infants; the risk associated with any newly emerging infectious disease (EID) is likely unknown at the time of its emergence. While the ongoing SARS-CoV-2 pandemic shows that the development of vaccines against new pathogens can be considerably accelerated, the immunization of pregnant women generally lags behind the general population. Guided by the priority pathogen list for WHO's R&D Blueprint for Action to Prevent Epidemics, this workshop sought to define the evidence needed for use of vaccines against EIDs in pregnant and lactating women, using Lassa fever as a model. Close to 60 maternal immunization (MI) and vaccine safety experts, regulators, vaccine developers, Lassa fever experts, and investigators from Lassa-affected countries examined the critical steps for vaccine development and immunization decisions for pregnant and lactating women. This paper reports on key themes and recommendations from the workshop. Current practice still assumes the exclusion of pregnant women from early vaccine trials. A shift in paradigm is needed to progress towards initial inclusion of pregnant women in Phase 2 and 3 trials. Several practical avenues were delineated. Participants agreed that vaccine platforms should be assessed early for their suitability for maternal immunization. It was noted that, in some cases, nonclinical data derived from assessing a given platform using other antigens may be adequate evidence to proceed to a first clinical evaluation and that concurrence from regulators may be sought with supporting rationale. For clinical trials, essential prerequisites such as documenting the disease burden in pregnant women, study site infrastructure, capabilities, and staff experience were noted. Early and sustained communication with the local community was considered paramount in any program for the conduct of MI trials and planned vaccine introduction.

Licensed and Recommended Inactivated Oral CholeraVaccines: From Development to Innovative Deployment

Cholera is a disease of poverty and occurs where there is a lack of access to clean water and adequate sanitation. Since improved water supply and sanitation infrastructure cannot be implemented immediately in many high-risk areas, vaccination against cholera is an important additional tool for prevention and control. We describe the development of licensed and recommended inactivated oral cholera vaccines (OCVs), including the results of safety, efficacy and effectiveness studies and the creation of the global OCV stockpile. Over the years, the public health strategy for oral cholera vaccination has broadened-from purely pre-emptive use to reactive deployment to help control outbreaks. Limited supplies of OCV doses continues to be an important problem. We discuss various innovative dosing and delivery approaches that have been assessed and implemented and evidence of herd protection conferred by OCVs. We expect that the demand for OCVs will continue to increase in the coming years across many countries.

Pregnant women & vaccines against emerging epidemic threats: Ethics guidance for preparedness, research, and response

Zika virus, influenza, and Ebola have called attention to the ways in which infectious disease outbreaks can severely - and at times uniquely - affect the health interests of pregnant women and their offspring. These examples also highlight the critical need to proactively consider pregnant women and their offspring in vaccine research and response efforts to combat emerging and re-emerging infectious diseases. Historically, pregnant women and their offspring have been largely excluded from research agendas and investment strategies for vaccines against epidemic threats, which in turn can lead to exclusion from future vaccine campaigns amidst outbreaks. This state of affairs is profoundly unjust to pregnant women and their offspring, and deeply problematic from the standpoint of public health. To ensure that the needs of pregnant women and their offspring are fairly addressed, new approaches to public health preparedness, vaccine research and development, and vaccine delivery are required. This Guidance offers 22 concrete recommendations that provide a roadmap for the ethically responsible, socially just, and respectful inclusion of the interests of pregnant women in the development and deployment of vaccines against emerging pathogens. The Guidance was developed by the Pregnancy Research Ethics for Vaccines, Epidemics, and New Technologies (PREVENT) Working Group - a multidisciplinary, international team of 17 experts specializing in bioethics, maternal immunization, maternal-fetal medicine, obstetrics, pediatrics, philosophy, public health, and vaccine research and policy - in consultation with a variety of external experts and stakeholders.

Pregnancy outcomes after a mass vaccination campaign with an oral cholera vaccine: a systematic review and meta-analysis

BACKGROUND

Cholera has harmful effects on the fetus but safety data on the oral cholera vaccine in pregnant women are controversial.

OBJECTIVES

We conducted the first meta-analysis of studies in pregnant women comparing the effect of oral cholera vaccination on pregnancy outcomes with unvaccinated women. Outcomes of interest were adverse pregnancy outcome, miscarriage, stillbirth, preterm delivery, low birthweight, abortion and malformation.

SEARCH STRATEGY

The search was run in MEDLINE/PubMed, SCOPUS and Embase databases from inception up to December 2019.

SELECTION CRITERIA

Inclusion criteria were: (1) studies that investigated the association between oral cholera vaccines and adverse pregnancy outcomes; (2) studies that reported outcomes with appropriate estimates; and (3) studies that contained an unvaccinated control group.

DATA COLLECTION AND ANALYSIS

A random-effects model (DerSimonian and Laird) was run to evaluate the overall treatment effect (relative risk, RR). The PRISMA statement was followed in reporting this meta-analysis.

MAIN RESULTS

Five studies included in meta-analysis with 5584 women (2920 exposed and 2664 not exposed). No significant increase in adverse pregnancy outcome (RR 1.03, 95% CI 0.79-1.34), miscarriage (RR 1.15, 95% CI 0.84-1.57) or stillbirth (RR 1.11, 95% CI 0.69-1.80) following cholera vaccine administration was found compared with control group. There was also no association with an increased risk of preterm delivery (RR 0.61, 95% CI 0.35-1.06) low birthweight (RR 0.84, 95% CI 0.56- 1.26), accidental abortion (RR 1.02, 95% CI 0.77-1.35) or malformation (RR 0.70, 95% CI 0.22-2.25).

CONCLUSIONS

This study shows no evidence of an association between oral cholera vaccination and adverse pregnancy outcomes. The findings do not rigorously exclude the possibility that the vaccine protocol may result in some degree of harm.

TWEETABLE ABSTRACT

There is no evidence of an association between oral cholera vaccination and adverse pregnancy outcomes. The findings do not rigorously exclude the possibility that the vaccine protocol may result in some degree of harm.

Global oral cholera vaccine use, 2013-2018

Vaccination is a key intervention to prevent and control cholera in conjunction with water, sanitation and hygiene activities. An oral cholera vaccine (OCV) stockpile was established by the World Health Organization (WHO) in 2013. We reviewed its use from July 2013 to all of 2018 in order to assess its role in cholera control. We computed information related to OCV deployments and campaigns conducted including setting, target population, timelines, delivery strategy, reported adverse events, coverage achieved, and costs. In 2013-2018, a total of 83,509,941 OCV doses have been requested by 24 countries, of which 55,409,160 were approved and 36,066,010 eventually shipped in 83 deployments, resulting in 104 vaccination campaigns in 22 countries. OCVs had in general high uptake (mean administrative coverage 1st dose campaign at 90.3%; 2nd dose campaign at 88.2%; mean survey-estimated two-dose coverage at 69.9%, at least one dose at 84.6%) No serious adverse events were reported. Campaigns were organized quickly (five days median duration). In emergency settings, the longest delay was from the occurrence of the emergency to requesting OCV (median: 26 days). The mean cost of administering one dose of vaccine was 2.98 USD. The OCV stockpile is an important public health resource. OCVs were generally well accepted by the population and their use demonstrated to be safe and feasible in all settings. OCV was an inexpensive intervention, although timing was a limiting factor for emergency use. The dynamic created by the establishment of the OCV stockpile has played a role in the increased use of the vaccine by setting in motion a virtuous cycle by which better monitoring and evaluation leads to better campaign organization, better cholera control, and more requests being generated. Further work is needed to improve timeliness of response and contextualize strategies for OCV delivery in the various settings.

Current and future cholera vaccines

Cholera remains a major global public health problem that is primarily linked to insufficient access to safe water and proper sanitation. Oral Cholera Vaccine (OCV) has been recommended as an additional public health tool along with WASH in cholera endemic countries and in areas at risk for outbreaks. The new generation OCV is safe and offers good protection in older children and adults while limited protection in younger children less than five years of age has been observed. The combination of direct vaccine protection and vaccine herd immunity effects makes OCV highly cost-effective and, therefore, attractive for use in developing countries. Additionally, in recent studies OCV was safe in pregnant women, supporting its use in pregnant women in cholera endemic countries. However, knowledge need to be developed for current vaccines for their prolonged duration of protection and vaccines need improvements for better immune response in younger children. A single dose vaccination regimen would be more cost-effective and easier to deliver. Recent approaches have focused on designing genetically attenuated cholera strains for use in single-dose cholera vaccines. The global demand for OCV has been boosted by the WHO recommendation to use OCV and is driven largely by epidemics and outbreaks and has been increasing due to the availability of cheaper easy-to-use vaccines, feasibility of mass OCV vaccination campaigns, demonstration of protection to underserved population in precarious situations, and vaccine costs being borne by Gavi (Vaccine Alliance). For rapid access in emergency and equitable distribution of OCV in cholera-endemic low-income countries, a global OCV stockpile was established in 2013 with support from the Global Alliance for Vaccines and Immunization. The three WHO-prequalified vaccines are Dukoral®, Shanchol™, Euvichol® (and Euvichol® Plus presentation), the latter two being included in the stockpile.

Safety of a bivalent, killed, whole-cell oral cholera vaccine in pregnant women in Bangladesh: evidence from a randomized placebo-controlled trial

BACKGROUND

Cholera increases the risk of harmful effects on foetuses. We prospectively followed pregnant women unaware of their pregnancy status who received a study agent in a clinical trial evaluating the association between exposure to an oral cholera vaccine (OCV) and foetal survival.

METHODS

Study participants were selected from a randomized placebo-controlled trial conducted in Dhaka, Bangladesh. The vaccination campaign was conducted between January 10 and February 4, 2014. We enrolled women who were exposed to an OCV or placebo during pregnancy (Cohort 1) and women who were pregnant after the vaccination was completed (Cohort 2). Our primary endpoint was pregnancy loss (spontaneous miscarriage or stillbirth), and the secondary endpoints were preterm delivery and low birth weight. We employed a log-binomial regression to calculate the relative risk of having adverse outcomes among OCV recipients compared to that among placebo recipients.

RESULT

There were 231 OCV and 234 placebo recipients in Cohort 1 and 277 OCV and 299 placebo recipients in Cohort 2. In Cohort 1, the incidence of pregnancy loss was 113/1000 and 115/1000 among OCV and placebo recipients, respectively. The adjusted relative risk for pregnancy loss was 0.97 (95% CI: 0.58-1.61; p = 0.91) in Cohort 1. We did not observe any variation in the risk of pregnancy loss between the two cohorts. The risks for preterm delivery and low birth weight were not significantly different between the groups in both cohorts.

CONCLUSIONS

Our study provides additional evidence that exposure to an OCV during pregnancy does not increase the risk of pregnancy loss, preterm delivery, or low birth weight, suggesting that pregnant women in cholera-affected regions should not be excluded in a mass vaccination campaign.

TRIAL REGISTRATION

The study is registered at ( http://clinicaltrials.gov ). Identifier: NCT02027207 .

Oral cholera vaccines and their impact on the global burden of disease

With one-third of nations at risk of cholera, we can expect to experience massive, rapidly disseminated, and prolonged cholera outbreaks such as those recently experienced in Yemen and Haiti. The prevention of cholera outbreaks like these includes the provision of potable water, sanitation, and hygiene (WASH). This approach has been known for generations. However, it will be many years before universal global access to WASH is achieved. While working toward universal WASH, study data has shown that licensed and WHO prequalified cholera vaccines are important tools for cholera prevention. Oral inactivated whole-cell vaccines such as Shanchol and Euvichol-plus provide well-documented direct benefits to vaccine recipients and to the unimmunized through herd protection. Manufacturers have now increased the cholera vaccine supply, and since 2013 vaccine doses have been available for emergency and endemic control through a global stockpile. Advances in packaging and vaccine temperature control, reduced vaccine costs, the inclusion of pregnant women in vaccine campaigns, and a targeted approach to high incidence endemic areas are further increasing the usefulness of these vaccines for reducing the global cholera burden.

Oral cholera vaccine in cholera prevention and control, Malawi

Problem

With limited global supplies of oral cholera vaccine, countries need to identify priority areas for vaccination while longer-term solutions, such as water and sanitation infrastructure, are being developed.

Approach

In 2017, Malawi integrated oral cholera vaccine into its national cholera control plan. The process started with a desk review and analysis of previous surveillance and risk factor data. At a consultative meeting, researchers, national health and water officials and representatives from nongovernmental and international organizations reviewed the data and local epidemiological knowledge to determine priority districts for oral cholera vaccination. The final stage was preparation of an application to the global oral cholera vaccine stockpile for non-emergency use.

Local setting

Malawi collects annual data on cholera and most districts have reported cases at least once since the 1970s.

Relevant changes

The government’s application for 3.2 million doses of vaccine to be provided over 20 months in 12 districts was accepted in April 2017. By April 2018, over 1 million doses had been administered in five districts. Continuing surveillance in districts showed that cholera outbreaks were notably absent in vaccinated high-risk areas, despite a national outbreak in 2017–2018.

Lessons learnt

Augmenting advanced mapping techniques with local information helped us extend priority areas beyond those identified as high-risk based on cholera incidence reported at the district level. Involvement of the water, sanitation and hygiene sectors is key to ensuring that short-term gains from cholera vaccine are backed by longer-term progress in reducing cholera transmission.

Molecular dynamics simulation (MDS) analysis of Vibrio cholerae ToxT virulence factor complexed with docked potential inhibitors

The ToxT transcription factor mediates the transcription of the two major virulence factors in Vibrio cholerae. It has a DNA binding domain made of α4, α5, α6, α7, α8, α9 and α10 helices that is responsible for the transcription of virulence genes. Therefore, it is of interest to screen ToxT against the ZINC ligand database containing data for a million compounds. The QSAR model identified 40 top hits for ToxT. Two target protein complexes with ligands Lig N1 and Lig N2 with high score were selected for molecular dynamics simulation. Simulation data shows that ligands are stable in the DNA binding domain of ToxT. Moreover, Lig N1 and Lig N2 passed pharmacological as well as ADME filters along with g-mmpbsa analysis with binding affinity of -199.831 kJ/mol for Lig N1 and - 286.951 kJ/mol for Lig N2. Moreover, no Lipinski and PhysChem violations were identified. It is further observed that these compounds were not inhibitors of P-glycoprotein, CYP450 and renal organic cation transporters. The LD50 of 2.5804 mol/kg for Lig N1 and 2.7788 mol/kg for Lig N2 was noted with acceptable toxicity index.

Maternal Immunization: New Perspectives on Its Application Against Non-Infectious Related Diseases in Newborns

The continuous evolution in preventive medicine has anointed vaccination a versatile, human-health improving tool, which has led to a steady decline in deaths in the developing world. Maternal immunization represents an incisive step forward for the field of vaccination as it provides protection against various life-threatening diseases in pregnant women and their children. A number of studies to improve prevention rates and expand protection against the largest possible number of infections are still in progress. The complex unicity of the mother-infant interaction, both during and after pregnancy and which involves immune system cells and molecules, is an able partner in the success of maternal immunization, as intended thus far. Interestingly, new studies have shed light on the versatility of maternal immunization in protecting infants from non-infectious related diseases, such as allergy, asthma and congenital metabolic disorders. However, barely any attempt at applying maternal immunization to the prevention of childhood cancer has been made. The most promising study reported in this new field is a recent proof of concept on the efficacy of maternal immunization in protecting cancer-prone offspring against mammary tumor progression. New investigations into the possibility of exploiting maternal immunization to prevent the onset and/or progression of neuroblastoma, one of the most common childhood malignancies, are therefore justified. Maternal immunization is presented in a new guise in this review. Attention will be focused on its versatility and potential applications in preventing tumor progression in neuroblastoma-prone offspring.