Impaired immune response to natural infection as a correlate of vaccine failure in a field trial of killed oral cholera vaccines

Duped by dumping syndrome: non-endemic Vibrio cholerae bacteremia in an immunocompetent host with gastric bypass surgery, a case report

Extra-intestinal infection with non-O1/non-O139 strains of Vibrio cholerae (NOVC) is rare, though bacteremia and hepatobiliary manifestations have been reported. Reduced stomach acid, or hypochlorhydria, can increase risk of V. cholerae infection. We describe a 42-year-old woman with hypochlorhydria due to untreated Helicobacter pylori infection, gastric-bypass surgery, and chronic proton pump inhibitors (PPI) exposure, who developed acute diarrhoea following raw oyster consumption. Her symptoms were attributed to rapid gastric emptying (dumping syndrome) after a negative limited stool work-up. She had persistent diarrhoea, weight loss, and after 5 months was admitted with acute cholecystitis and NOVC bacteremia, requiring cholecystectomy. This is the first reported case of NOVC bacteremia and cholecystitis in a patient with gastric bypass. This case highlights the potential for NOVC biliary carriage, the role of hypochlorhydria as a risk factor for Vibrio infection, and the importance of excluding infectious diarrhoea in patients with new onset of symptoms compatible with dumping syndrome and a relevant travel history.

Individual and Household Risk Factors for Symptomatic Cholera Infection: A Systematic Review and Meta-analysis

Background

Cholera has caused 7 global pandemics, including the current one which has been ongoing since 1961. A systematic review of risk factors for symptomatic cholera infection has not been previously published.

Methods

In accordance with PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines, we performed a systematic review and meta-analysis of individual and household risk factors for symptomatic cholera infection.

Results

We identified 110 studies eligible for inclusion in qualitative synthesis. Factors associated with symptomatic cholera that were eligible for meta-analysis included education less than secondary level (summary odds ratio [SOR], 2.64; 95% confidence interval [CI], 1.41-4.92; I2 = 8%), unimproved water source (SOR, 3.48; 95% CI, 2.18-5.54; I2 = 77%), open container water storage (SOR, 2.03; 95% CI, 1.09-3.76; I2 = 62%), consumption of food outside the home (SOR, 2.76; 95% CI, 1.62-4.69; I2 = 64%), household contact with cholera (SOR, 2.91; 95% CI, 1.62-5.25; I2 = 89%), water treatment (SOR, 0.37; 95% CI, .21-.63; I2 = 74%), and handwashing (SOR, 0.29; 95% CI, .20-.43; I2 = 37%). Other notable associations with symptomatic infection included income/wealth, blood group, gastric acidity, infant breastfeeding status, and human immunodeficiency virus infection.

Conclusions

We identified potential risk factors for symptomatic cholera infection including environmental characteristics, socioeconomic factors, and intrinsic patient factors. Ultimately, a combination of interventional approaches targeting various groups with risk-adapted intensities may prove to be the optimal strategy for cholera control.

Oral vaccines for preventing cholera

EDITORIAL NOTE

This review is superseded by the published Cochrane Review, Saif‐Ur‐Rahman 2024 [https://doi.org/10.1002/14651858.CD014573], which considers only the oral killed vaccines because the live oral vaccines do not have World Health Organization (WHO) prequalification. Saif‐Ur‐Rahman 2024 also considered only currently available WHO pre‐qualified oral killed cholera vaccines (Dukoral, Shanchol, and Euvichol/Euvichol‐Plus).

BACKGROUND

Cholera is a cause of acute watery diarrhoea which can cause dehydration and death if not adequately treated. It usually occurs in epidemics, and is associated with poverty and poor sanitation. Effective, cheap, and easy to administer vaccines could help prevent epidemics.

OBJECTIVES

To assess the effectiveness and safety of oral cholera vaccines in preventing cases of cholera and deaths from cholera.

SEARCH STRATEGY

In October 2010, we searched the Cochrane Infectious Disease Group Specialized Register; Cochrane Central Register of Controlled Trials (CENTRAL); MEDLINE; EMBASE; LILACS; the metaRegister of Controlled Trials (mRCT), and the WHO International Clinical Trials Registry Platform (ICTRP) for relevant published and ongoing trials.

SELECTION CRITERIA

Randomized or quasi-randomized controlled trials of oral cholera vaccines in healthy adults and children.

DATA COLLECTION AND ANALYSIS

Each trial was assessed for eligibility and risk of bias by two authors working independently. Data was extracted by two independent reviewers and analysed using the Review Manager 5 software. Outcomes are reported as vaccine protective efficacy (VE) with 95% confidence intervals (CIs).

MAIN RESULTS

Seven large efficacy trials, four small artificial challenge studies, and twenty-nine safety trials contributed data to this review.Five variations of a killed whole cell vaccine have been evaluated in large scale efficacy trials (four trials, 249935 participants). The overall vaccine efficacy during the first year was 52% (95% CI 35% to 65%), and during the second year was 62% (95% CI 51% to 62%). Protective efficacy was lower in children aged less than 5 years; 38% (95% CI 20% to 53%) compared to older children and adults; 66% (95% CI 57% to 73%).One trial of a killed whole cell vaccine amongst military recruits demonstrated 86% protective efficacy (95% CI 37% to 97%) in a small epidemic occurring within 4 weeks of the 2-dose schedule (one trial, 1426 participants). Efficacy data is not available beyond two years for the currently available vaccine formulations, but based on data from older trials is unlikely to last beyond three years.The safety data available on killed whole cell vaccines have not demonstrated any clinically significant increase in adverse events compared to placebo.Only one live attenuated vaccine has reached Phase III clinical evaluation and was not effective (one trial, 67508 participants). Two new candidate live attenuated vaccines have demonstrated clinical effectiveness in small artificial challenge studies, but are still in development.

AUTHORS' CONCLUSIONS

The currently available oral killed whole cell vaccines can prevent 50 to 60% of cholera episodes during the first two years after the primary vaccination schedule. The impact and cost-effectiveness of adopting oral cholera vaccines into the routine vaccination schedule of endemic countries will depend on the prevalence of cholera, the frequency of epidemics, and access to basic services providing rapid rehydration therapy.

Children with the Le(a+b-) blood group have increased susceptibility to diarrhea caused by enterotoxigenic Escherichia coli expressing colonization factor I group fimbriae

Recent studies have shown that children with blood group A have increased susceptibility to enterotoxigenic Escherichia coli (ETEC) diarrhea and that Lewis blood group "a" antigen (Le(a)) may be a candidate receptor for ETEC colonization factor (CF) antigen I (CFA/I) fimbriae. Based on these findings, we have attempted to determine if children with the Le(a+b-) phenotype may be more susceptible to diarrhea caused by ETEC, in particular ETEC expressing CFA/I and related fimbriae of the CFA/I group, than Le(a-b+) children. To test this hypothesis, we have determined the Lewis antigen expression in 179 Bangladeshi children from a prospective birth cohort study in urban Dhaka in which ETEC expressing major CFs such as CFA/I, CS3, CS5, and CS6 was the most commonly isolated diarrhea pathogen during the first 2 years of life. The Lewis blood group phenotypes were determined by a dot blot immunoassay using saliva samples and by a tube agglutination test using fresh red blood cells. The results indicate that Le(a+b-) children more often had symptomatic than asymptomatic ETEC infections (P < 0.001), whereas symptomatic and asymptomatic ETEC infections were equally frequent in Le(a-b+) children. We also show that children with the Le(a+b-) blood type had significantly higher incidences of diarrhea caused by ETEC expressing fimbriae of the CFA/I group than Le(a-b+) children (P < 0.001). In contrast, we did not find any association between the Lewis blood group phenotype and diarrhea caused by ETEC expressing CS6 or rotavirus.

Disease burden due to enterotoxigenic Escherichia coli in the first 2 years of life in an urban community in Bangladesh

A cohort of 321 children was followed from birth up to 2 years of age to determine the incidence of enterotoxigenic Escherichia coli (ETEC) in Bangladesh. The average number of diarrheal days and incidence rates were 6.6 and 2.3/child/year, respectively. ETEC was the most common pathogen and was isolated in 19.5% cases, with an incidence of 0.5 episode/child/year. The prevalence of rotavirus diarrhea was lower (10%). ETEC expressing the heat-stable enterotoxin (ST) was predominant. Strains isolated from diarrheal cases were positive for colonization factors (CFs) in higher frequency (66%) than from healthy children (33%) (P < 0.001). The heat-labile toxin (LT)-positive strains from healthy children were more often CF negative (92%) than those isolated from children with diarrhea (73%) (P < 0.001). In children with symptomatic or asymptomatic infections by CFA/I, CS1 plus CS3, CS2 plus CS3, or CS5 plus CS6 strains, a repeat episode of diarrhea or infection by the homologous CF type was uncommon. Repeat symptomatic infections were noted mostly for LT- and ST-expressing ETEC. ETEC diarrhea was more prevalent in children in the A and AB groups than in those in the O blood group (P = 0.032 to 0.023). Children with ETEC diarrhea were underweight and growth stunted at the 2-year follow-up period, showing the importance of strategies to prevent and decrease ETEC diarrheal morbidity in children.

Live attenuated oral cholera vaccines

Live, orally administered, attenuated vaccine strains of Vibrio cholerae have many theoretical advantages over killed vaccines. A single oral inoculation could result in intestinal colonization and rapid immune responses, obviating the need for repetitive dosing. Live V. cholerae organisms can also respond to the intestinal environment and immunological exposure to in vivo expressed bacterial products, which could result in improved immunological protection against wild-type V. cholerae infection. The concern remains that live oral cholera vaccines may be less effective among partially immune individuals in cholera endemic areas as pre-existing antibodies can inhibit live organisms and decrease colonization of the gut. A number of live oral cholera vaccines have been developed to protect against cholera caused by the classical and El Tor serotypes of V. cholerae O1, including CVD 103-HgR, Peru-15 and V. cholerae 638. A number of live oral cholera vaccines have also been similarly developed to protect against cholera caused by V. cholerae O139, including CVD 112 and Bengal-15. Live, orally administered, attenuated cholera vaccines are in various stages of development and evaluation.

New developments in the understanding of cholera

Recent advances in prevention and treatment of cholera have occurred in the areas of vaccine testing, modifications of oral-rehydration solutions (ORS), and antimicrobial treatment. Oral vaccines consisting of killed whole bacterial cells (WC) with and without the B-subunit of cholera toxin (BS) were shown to be effective in large trials in Bangladesh, Peru, and Vietnam. However, the trials did not resolve whether two or three doses of vaccine are required and whether BS adds significantly to the immune protection of WC. Live, attenuated bacterial vaccines that are immunogenic and have been shown protective in human volunteer studies are candidates for future field trials. Rehydration of patients is a life- saving effort. The best ORS contains rice powder in place of glucose, and solutions with reduced osmolarity (245 mOsm/L, sodium 75 mEq/L) are as effective as standard ORS. Ciprofloxacin in a single dose is effective in adults, and erythromycin or ampicillin in multiple doses is effective in children.

Vaccines for preventing cholera

BACKGROUND

Oral cholera vaccines (either killed whole cell or live recombinant vaccines) are newer alternatives to the parenteral vaccines which have been thought to confer only moderate and short-term immunity.

OBJECTIVES

The objective of this review was to assess the effect of cholera vaccines in preventing cases of cholera and preventing deaths.

SEARCH STRATEGY

We searched the Cochrane Infectious Diseases Group trials register, Medline, Embase and reference lists of articles. We handsearched the journal Vaccine, contacted researchers in the field and manufacturers.

SELECTION CRITERIA

Randomised and quasi-randomised studies comparing cholera vaccines (killed or live) with placebo, control vaccines or no intervention, or comparing types, doses or schedules of cholera vaccine. We included adults and children irrespective of immune status or special risk category.

DATA COLLECTION AND ANALYSIS

Data extraction and assessment of trial quality was done independently by two reviewers.

MAIN RESULTS

Thirty-two trials were included. Seventeen efficacy trials of relatively good quality, testing parenteral and oral killed whole cell vaccines and involving over 2. 6 million adults, children and infants were included. Nineteen safety trials have been conducted for both types of killed whole cell vaccines and for live vaccines and have involved 11,459 people. For all types of vaccines compared to placebo, the relative risk of contracting cholera at 12 months was 0.49, 95% confidence interval 0. 41 to 0.59 (random effects model). This translates to an efficacy of 51%, 95% confidence interval 41% to 59%. Both parenteral and oral administration were relatively efficacious, but significant protection extended into the third year for oral killed whole cell vaccines. Children under 5 were only protected for up to a year, while older children or adults were protected for up to three years. Parenteral killed whole cell vaccines were associated with increased systemic and local adverse effects compared to placebo. Oral killed whole cell vaccines or oral live vaccines were not.

REVIEWER'S CONCLUSIONS

Cholera killed whole cell vaccines appear to be relatively effective and safe. Live oral recombinant vaccines appear to be safe, but efficacy data are not available. Protection against cholera appears to persist for up to two years following a single dose of vaccine, and for three to four years with an annual booster.

Re-emergence of Cholera Vaccine

Although epidemic cholera was first described in 1817, the disease probably has been common in the Indian subcontinent since ancient times.1 Until recently, a single bacterial type (Vibrio cholerae 01) has been responsible for each of the seven recorded cholera pandemics. The current epidemic began in Celebes (Sulawesi), Indonesia, in 1961, and is currently raging through all continents.2 During the 1990s, over 1 million cholera cases have been reported from Latin America, 2000 from Ukraine and the Russian Republic during 1994 alone (GIDEON computer software, C.Y. Informatics, Ramat Hasharon, Israel). Of the 208,755 cases of cholera (5034 fatal) officially reported to the World Health Organization in 1995,3 41.1% were from Latin America, 34.0% from Africa, 24.4% from Asia, and 0.5% from Europe and Oceania. Interest in our own country of Israel stems from the popularity of tourism (over 1 million travelers exit Israel yearly) and the presence of disease in neighboring areas. Following an epidemic of 397 cases in Jerusalem during 1970, periodic outbreaks have occurred in Gaza, Judea and Samaria.4 Three tourists returned with the infection to Israel during the 1980s, all from Egypt (which officially claims to have no cholera).5 Despite universal interest in this ancient disease, medical science has long been frustrated in its search for an effective vaccine. The most important 'vaccine' against cholera is common sense, and consists of intelligent eating and drinking while in endemic areas. For example, local raw fish (ceviche) is a common source of the disease in Latin America, while shellfish (particularly oysters) are often implicated along the American Gulf Coast. Virtually all forms of water purification are effective against Vibrio cholerae. Although antibiotic prophylaxis might be considered in some circumstances (doxycycline; or a quinolone in areas of tetracycline resistance), it is not routinely advocated.