Gut Microbiota and Development of Vibrio cholerae-Specific Long-Term Memory B Cells in Adults after Whole-Cell Killed Oral Cholera Vaccine.

Cholera is a diarrheal disease caused by Vibrio cholerae that continues to be a major public health concern in populations without access to safe water. IgG- and IgA-secreting memory B cells (MBC) targeting the V. cholerae O-specific polysaccharide (OSP) correlate with protection from infection in persons exposed to V. cholerae and may be a major determinant of long-term protection against cholera. Shanchol, a widely used oral cholera vaccine (OCV), stimulates OSP MBC responses in only some people after vaccination, and the gut microbiota is a possible determinant of variable immune responses observed after OCV. Using 16S rRNA sequencing of feces from the time of vaccination, we compared the gut microbiota among adults with and without MBC responses to OCV. Gut microbial diversity measures were not associated with MBC isotype or OSP-specific responses, but individuals with a higher abundance of Clostridiales and lower abundance of Enterobacterales were more likely to develop an MBC response. We applied protein-normalized fecal supernatants of high and low MBC responders to THP-1-derived human macrophages to investigate the effect of microbial factors at the time of vaccination. Feces from individuals with higher MBC responses induced significantly different IL-1ß and IL-6 levels than individuals with lower responses, indicating that the gut microbiota at the time of vaccination may "prime" the mucosal immune response to vaccine antigens. Our results suggest the gut microbiota could impact immune responses to OCVs, and further study of microbial metabolites as potential vaccine adjuvants is warranted.

Cost-effectiveness of a reactive oral cholera immunization campaign using Shanchol™ in Malawi.

BACKGROUND: Oral cholera vaccines (OCV) have been recommended as additional measures for the prevention of cholera. However, little is known about the cost-effectiveness of OCV use in sub-Saharan Africa, particularly in reactive outbreak contexts. This study aimed to investigate the cost-effectiveness of the use of OCV Shanchol in response to a cholera outbreak in the Lake Chilwa area, Malawi. METHODS: The Excel-based Vaccine Introduction Cost-Effectiveness model was used to assess the cost-effectiveness ratios with and without indirect protection. Model input parameters were obtained from cost evaluations and epidemiological studies conducted in Malawi and published literature. One-way sensitivity and threshold analyses of cost-effectiveness ratios were performed. RESULTS: Compared with the reference scenario i.e. treatment of cholera cases, the immunization campaign would have prevented 636 and 1 020 cases of cholera without and with indirect protection, respectively. The cost-effectiveness ratios were US$19 212 per death, US$500 per case, and US$738 per DALY averted without indirect protection. They were US$10 165 per death, US$264 per case, and US$391 per DALY averted with indirect protection. The net cost per DALY averted was sensitive to four input parameters, including case fatality rate, duration of immunity (vaccine's protective duration), discount rate and cholera incidence. CONCLUSION: Relative to the Malawi gross domestic product per capita, the reactive OCV campaign represented a cost-effective intervention, particularly when considering indirect vaccine effects. Results will need to be assessed in other settings, e.g., during campaigns implemented directly by the Ministry of Health rather than by international partners.

Delivery cost analysis of a reactive mass cholera vaccination campaign: a case study of Shanchol™ vaccine use in Lake Chilwa, Malawi.

BACKGROUND: Cholera is a diarrheal disease that produces rapid dehydration. The infection is a significant cause of mortality and morbidity. Oral cholera vaccine (OCV) has been propagated for the prevention of cholera. Evidence on OCV delivery cost is insufficient in the African context. This study aims to analyze Shanchol vaccine delivery costs, focusing on the vaccination campaign in response of a cholera outbreak in Lake Chilwa, Malawi. METHODS: The vaccination campaign was implemented in two rounds in February and March 2016. Structured questionnaires were used to collect costs incurred for each vaccination related activity, including vaccine procurement and shipment, training, microplanning, sensitization, social mobilization and vaccination rounds. Costs collected, including financial and economic costs were analyzed using Choltool, a standardized cholera cost calculator. RESULTS: In total, 67,240 persons received two complete doses of the vaccine. Vaccine coverage was higher in the first round than in the second. The two-dose coverage measured with the immunization card was estimated at 58%. The total financial cost incurred in implementing the campaign was US$480275 while the economic cost was US$588637. The total financial and economic costs per fully vaccinated person were US$7.14 and US$8.75, respectively, with delivery costs amounting to US$1.94 and US$3.55, respectively. Vaccine procurement and shipment accounted respectively for 73% and 59% of total financial and economic costs of the total vaccination campaign costs while the incurred personnel cost accounted for 13% and 29% of total financial and economic costs. Cost for delivering a single dose of Shanchol was estimated at US$0.97. CONCLUSION: This study provides new evidence on economic and financial costs of a reactive campaign implemented by international partners in collaboration with MoH. It shows that involvement of international partners' personnel may represent a substantial share of campaign's costs, affecting unit and vaccine delivery costs.

Immunogenicity of the Bivalent Oral Cholera Vaccine Shanchol in Haitian Adults With HIV Infection.

We evaluated immune responses following bivalent oral cholera vaccination (Shanchol [Shantha Biotechnics]; BivWC) in a cohort of 25 human immunodeficiency virus (HIV)-infected adults in Haiti. Compared with adults without HIV infection, vaccination in HIV-infected individuals resulted in lower vibriocidal responses against Vibrio cholerae O1, and there was a positive relationship between the CD4(+) T-cell count and vibriocidal responses following vaccination. Nevertheless, seroconversion occurred at a rate of 65% against the Ogawa serotype and 74% against the Inaba serotype in adults with HIV infection. These results suggest that the vaccine retains substantial immunogenicity in adults with HIV infection and may benefit this population by protecting against cholera.

Seroconversion and Kinetics of Vibriocidal Antibodies during the First 90 Days of Re-Vaccination with Oral Cholera Vaccine in an Endemic Population.

Despite the successful introduction of oral cholera vaccines, Zambia continues to experience multiple, sporadic, and protracted cholera outbreaks in various parts of the country. While vaccines have been useful in staying the cholera outbreaks, the ideal window for re-vaccinating individuals resident in cholera hotspot areas remains unclear. Using a prospective cohort study design, 225 individuals were enrolled and re-vaccinated with two doses of Shanchol™, regardless of previous vaccination, and followed-up for 90 days. Bloods were collected at baseline before re-vaccination, at day 14 prior to second dosing, and subsequently on days 28, 60, and 90. Vibriocidal assay was performed on samples collected at all five time points. Our results showed that anti-LPS and vibriocidal antibody titers increased at day 14 after re-vaccination and decreased gradually at 28, 60, and 90 days across all the groups. Seroconversion rates were generally comparable in all treatment arms. We therefore conclude that vibriocidal antibody titers generated in response to re-vaccination still wane quickly, irrespective of previous vaccination status. However, despite the observed decline, the levels of vibriocidal antibodies remained elevated over baseline values across all groups, an important aspect for Zambia where there is no empirical evidence as to the ideal time for re-vaccination.

Comparison of the immunogenicity and safety of Euvichol-Plus with Shanchol in healthy Indian adults and children: an open-label, randomised, multicentre, non-inferiority, parallel-group, phase 3 trial.

Background: Considering the cholera menace in India and to seek licensure of the oral cholera vaccine (OCV), Euvichol-Plus, we conducted a clinical trial to compare the immunogenicity and safety of Euvichol-Plus with Shanchol in healthy Indian adults and children. Methods: This phase 3, open-label, multicentre, randomised, non-inferiority, parallel-group, comparative study was conducted at seven sites across India involving 416 healthy adults (aged ≥18-60 years) and children (aged ≥1 to <18 years). Healthy individuals who agreed to participate through a voluntary written informed consent form along with oral or written assent (for children aged 7-18 years) were included. No assent was required for those <7 years, as consent was given by the legally acceptable representatives (LAR). Participants were randomised 1:1 to receive two doses of either Euvichol-Plus or Shanchol orally, 14 days apart. The first dose (1.5 ml) was administered on visit 1, and the second dose at 2 weeks after the first dose during visit 2. Participants were followed up telephonically for 3 consecutive days after each visit and returned for final assessment at 2 weeks after the second dose (visit 3). Blood samples were collected for immunogenicity assessment, and safety analyses were done during all the visits. The primary immunogenicity endpoint was the percentage of participants with ≥4-fold increase in anti-Vibrio cholerae (V. cholerae) O1 Ogawa and O1 Inaba (vibriocidal) antibody titres at 2 weeks after the second dose as compared to baseline titres prior to dosing. The secondary immunogenicity endpoints included the percentage of participants with ≥4-fold increase in anti-V. cholerae O139 antibody titres at 2 weeks after the second dose as compared to baseline titres, and geometric mean titres (GMT) and geometric mean ratios (GMR) as measured by anti-V. cholerae O1 Ogawa, O1 Inaba, and O139 antibody titres at 2 weeks after the second dose as compared to baseline titres. The safety endpoints included assessment of solicited, unsolicited adverse events (AEs), and serious adverse events (SAEs). The clinical trial was registered with the Clinical Trials Registry of India (CTRI/2021/08/035344). Findings: The study was performed in two age cohorts: cohort 1 (aged ≥18-60 years, 208 participants [104 in Euvichol-Plus group and 104 in Shanchol group]), and cohort 2 (aged ≥1 to <18 years, 208 participants [104 in Euvichol-Plus group and 104 in Shanchol group]). A total of 414 participants (Euvichol-Plus: 206 and Shanchol: 208) who completed the study (intention-to-treat and per-protocol set) were analysed to compare the vibriocidal titre as an index for immunogenicity. At 2 weeks after the second dose, the percentage of participants in the Euvichol-Plus group who reported a ≥4-fold increase in anti-V. cholerae antibody titres were 68.93% (O1 Ogawa) [95% CI 62.13%-75.18%], 66.02% (O1 Inaba) [95% CI 59.11%-72.46%], and 59.71% (O139) [95% CI 52.67%-66.47%] as compared to 63.94% (O1 Ogawa) [95% CI 57.01%-70.47%], 65.87% (O1 Inaba) [95% CI 58.99%-72.28%], and 56.25% (O139) [95% CI 49.22%-63.10%] in the Shanchol group. The lower limit of 95% CI for treatment difference for all the antibody titres was ≥10% (non-inferiority margin), demonstrating that Euvichol-Plus was non-inferior to Shanchol. The post-vaccination GMT (Day 14 and 28) were more than the pre-vaccination GMT for all three serotypes in both groups. The GMR obtained for Euvichol-Plus over Shanchol for O1 Ogawa, O1 Inaba, and O139 serotypes was >1, indicating non-inferiority of Euvichol-Plus to Shanchol. The safety cohort included 416 participants. Headache was the most common solicited AE, whereas cold and cough were the most common unsolicited AEs in both groups. Interpretation: Euvichol-Plus appears to be non-inferior to Shanchol in terms of immunogenicity and safety in healthy Indian adults and children. Funding: Techinvention Lifecare Private Limited, Mumbai, India.

Augmented immune responses to a booster dose of oral cholera vaccine in Bangladeshi children less than 5 years of age: Revaccination after an interval of over three years of primary vaccination with a single dose of vaccine.

We have earlier reported that a single dose of oral cholera vaccine (OCV) is protective in adults and children ≥5 years of age and sustained for 2 years. We enrolled participants (n = 240) from this study, between March-September 2017, over 3 years after receiving a primary single dose. Immune responses were measured in placebo group (Primary Immunization group: PI) and compared with those who received a single dose (Booster Immunization group: BI). The children were 4 to <5 years, 5 to <18 years and adults >18 years. Blood was collected at day 0 (before vaccination) and after receiving 1st and 2nd doses of OCV. Overall, the BI and PI groups showed vibriocidal antibody response after 1st and 2nd dose of vaccination in all age groups to V. cholerae O1 and O139. Young children in the BI group showed significantly higher vibriocidal antibody response two weeks after receiving the first dose as compared to PI group to LPS. Elevated plasma IgA responses to LPS after the first dose were observed among the BI group compared to the PI group among the young children. Mucosal antibody responses measured in fecal extracts showed similar increases as that of vibriocidal and LPS responses in the BI group. These results suggest a single boosting dose of OCV generated immune response in primed population >5 years of age who had earlier received OCV. However, young children who had received OCV earlier, boosting after a single dose, resulted in increased immune responses compared to the PI group. Further studies are needed to assess protection obtained from different strategies, especially for young children and to determine the numbers of primary and booster doses needed. In addition, more information is needed regarding the optimum interval between primary and booster doses to plan future interventions for cholera control. ClinicalTrials.gov Identifier: NCT02027207.

Bivalent oral cholera vaccine in participants aged 1 year and older in the Dominican Republic: A phase III, single-arm, safety and immunogenicity trial.

The Dominican Republic, historically non-endemic for cholera, is experiencing an ongoing cholera epidemic. We assessed the safety and immunogenicity of two doses of the killed bivalent (O1 and O139) whole-cell oral cholera vaccine (OCV) on day (D)0 and D14 in healthy participants aged ≥1 year. Immediate unsolicited systemic adverse events (AEs) were monitored up to 30 minutes and solicited systemic reactions, up to 7 days after each vaccination. Unsolicited AEs were recorded up to D14 (post-dose 1) and 30 days post-dose 2. A vibriocidal antibody assay with microtiter technique was used to measure serum antibodies to V. cholerae strains (O1 El Tor Inaba, O1 El Tor Ogawa, O139) on D0, D14 and D28. Geometric mean titers (GMTs) and seroconversion (≥4-fold increase from D0) rates were calculated. We recruited 336 participants; 112 in three age groups (1-4, 5-14 and ≥15 years). No safety concerns were observed. GMTs increased from baseline for all serotypes, with marked increases for O1 Inaba and Ogawa post-dose 1. Post-dose 2 GMTs tended to be equal or slightly lower, with ranges: O1 Inaba, 283 (95% confidence interval 191-419) to 612 (426-880); O1 Ogawa, 346 (223-536) to 754 (553-1028); and O139, 20.3 (13.5-30.6) to 43.8 (30.1-63.7). Seroconversion rates post-dose 2 for O1 Inaba and Ogawa were high (≥87%) for all age groups. OCV demonstrated an acceptable safety profile and robust immunogenicity in these participants, in-line with previous observations in epidemic and endemic settings.This study is registered on www.clinicaltrials.gov (NCT02434822).

Safety and immunogenicity of the killed bivalent (O1 and O139) whole-cell cholera vaccine in the Philippines.

The killed bivalent (O1 and O139) whole cell oral cholera vaccine (OCV) (Shanchol™) was first licensed in India in 2009 and World Health Organization pre-qualified in 2011. We assessed the safety and immunogenicity of this OCV in the Philippines. This was a phase IV, single-arm, descriptive, open-label study. We recruited 336 participants from 2 centers: 112 participants in each age group (1-4, 5-14 and ≥ 15 years). Participants received 2 OCV doses 14 d apart. Safety was monitored throughout the trial. Blood samples were collected at baseline (pre-vaccination) and 14 d after each dose. Serum vibriocidal antibody titers to V. cholerae O1 (El Tor Inaba and El Tor Ogawa) and O139 strains were assessed, with seroconversion defined as ≥ 4-fold increase from baseline in titers. No immediate unsolicited systemic adverse events/reactions were observed. Unsolicited systemic adverse events were mostly grade 1 intensity. One serious adverse event occurred after the first dose, but was unrelated to vaccination. High seroconversion rates (range 69-92%) were achieved against the O1 serotypes with a trend toward higher rates in the 1-4 y (86-92%) and 5-14 y (86-88%) age groups than the ≥ 15 y age group (69-83%). Lower seroconversion rates were achieved against the O139 serotype (35-70%), particularly in those aged ≥ 15 y (35-42%). The 2-dose regimen of the killed bivalent whole cell OCV was well-tolerated in this study conducted in the Philippines, a cholera-endemic country. Robust immune responses were observed even after a single-dose.

Safety of the oral cholera vaccine in pregnancy: Retrospective findings from a subgroup following mass vaccination campaign in Dhaka, Bangladesh.

BACKGROUND: Pregnant women are vulnerable to complications of cholera. Killed oral cholera vaccines (OCV) are not recommended for pregnant women though there is no evidence of harmful effects during pregnancy. We evaluated the effect of a killed OCV, Shanchol™, on pregnancy outcomes during an effectiveness trial of the vaccine in urban Bangladesh. METHODOLOGY: Individuals ⩾1year were invited to participate in the trial, conducted in 2011 in Dhaka, Bangladesh. Pregnancy by history was an exclusion criterion and all women of reproductive age (15-49years) were verbally questioned about pregnancy at enrollment and prior to vaccination. Out of 48,414 women of reproductive age 286 women received the OCV unknowingly while pregnant. Out of these, we could recruit 69 women defined as exposed to OCV. Accordingly, we selected 69 pregnant women randomly from those who did not take the OCV (non-exposed to OCV). We evaluated adverse pregnancy outcome (spontaneous miscarriages, still births, or congenital malformations) between those who were exposed to OCV and those who were not exposed to OCV. RESULTS: About 16% of pregnant women exposed to OCV had pregnancy loss, as compared to 12% of unvaccinated pregnant women (P=0.38). One congenital anomaly was observed and occurred in women non-exposed to OCV group. Models that adjusted for baseline characteristics that were unbalanced between the exposed and non-exposed groups, revealed a no elevation of risk of adverse pregnancy outcomes in vaccinees versus non-vaccinees (Adj. OR (95% CI): 0.45 (0.11-1.88). CONCLUSIONS: No excess of adverse fetal outcomes associated with receipt of OCV was observed in this study. TRIAL REGISTRATION: Clinical Trials.gov number NCT01339845.

Cholera Outbreak in Gaidataar: A Lesson for Further Strengthening the Task Force for Epidemic Management in Nepal.

Cholera is an acute enteric infection caused by the ingestion of bacterium Vibrio cholerae(1). Cholera is transmitted through contaminated food and water. Prevention and preparedness of cholera require a coordinated multi-disciplinary approach. The extremely short incubation period enhances the potentially explosive pattern of outbreaks. Cholera can lead to severe dehydration and death if left untreated. The laboratory testing is required for antimicrobial sensitivity testing and for confirming the end of an outbreak. Provision of safe drinking water, proper sanitation, and food safety are critical for preventing occurrence of cholera. Health education aims at communities adopting preventive behavior for averting contamination. Specific training for all the staffs about proper case management including avoidance of noso-comial infection (like face masks, gloves, antiseptic solution, hand scrubs). Sufficient pre-positioned medical supplies for case management (diarrhoeal disease kits, iv fluids, antibiotics, safety measures). Improved access to water, effective sanitation, proper waste management and vector control. Improved communication and public information. Oral Rehydration Salts can treat 80% of cholera1. Appropriate antibiotics can reduce the duration of purging. With a well and properly managed team of health experts with all essential medicines and a good rapid response team, any outbreak can be prevented, controlled and managed.

The oral cholera vaccine Shanchol™ when stored at elevated temperatures maintains the safety and immunogenicity profile in Bangladeshi participants.

BACKGROUND: The oral cholera vaccine (OCV), Shanchol™ has shown protective efficacy lasting up to 5 years, however, requirement for a cold chain limits its use in resource poor settings. The study was conducted to determine the safety and immunogenicity of Shanchol in adult participants in Bangladesh when stored at elevated temperatures. METHODS: The study was conducted in Mirpur, Dhaka. Four groups of healthy adult participants received two doses of Shanchol™, kept under standard storage temperature (Group A; 2-8°C) or at elevated temperatures (Group B, 25°C; Group C, 37°C; Group D, 42°C) for 14 days, respectively. Vaccine specific antibody responses were determined. FINDINGS: 145 participants were assigned to each group. Adverse events were mild not differing among groups. Vaccine stored at elevated temperatures remained stable with cumulative LPS content within admissible limits. Vibriocidal antibody responses were observed in all groups after each dose of vaccine at day 7 and 21 compared to pre-immune levels (P<0.001). Four-fold increases to Vibrio cholerae O1 Ogawa were observed at day 7 and/or day 21 after vaccination in the standard temperature and the three elevated temperature groups, with responder rates of; 76% (95% CI LB; 70%), 80% (95% CI LB; 74%), 69% (95% CI LB; 63%), and 74% (95% CI LB; 68%) in Groups A-D, respectively (P=0.240). Responses were also seen in all groups to V. cholerae O1 Inaba and V. cholerae O139 and in LPS specific IgA response to V. cholerae O1 antigens. INTERPRETATION: This is the first report to show that the OCV is stable at elevated temperatures, and the safety and immunogenicity profiles are not altered. This information will help formulate global policies for use of the vaccine at higher temperatures, resulting in easier distribution and vaccination costs and decrease logistical challenges to vaccine delivery. FUNDING: Bill & Melinda Gates Foundation. TRIAL REGISTRATION: Clinical Trials.gov number NCT01762930.

A randomized, non-inferiority trial comparing two bivalent killed, whole cell, oral cholera vaccines (Euvichol vs Shanchol) in the Philippines.

BACKGROUND: Currently, there are two oral cholera vaccines (OCV) that are prequalified by the World Health Organization. Both (Dukoral and Shanchol) have been proven to be safe, immunogenic, and effective. As the global supply of OCV remains limited, we assessed the safety and immunogenicity of a new low cost, killed, bivalent OCV (Euvichol) in the Philippines. METHODS: The randomized controlled trial was carried out in healthy Filipino adults and children. Two doses of either the current WHO prequalified OCV (Shanchol) or the same composition OCV being considered for WHO prequalification (Euvichol) were administered to participants. RESULTS: The pivotal study was conducted in total of 1263 healthy participants (777 adults and 486 children). No serious adverse reactions were elicited in either vaccine groups. Vibriocidal antibody responses to V. cholerae O1 Inaba following administration of two doses of Euvichol were non-inferior to those of Shanchol in adults (82% vs 76%) and children (87% vs 89%). Similar findings were observed for O1 Ogawa in adults (80% vs 74%) and children (91% vs 88%). CONCLUSION: A two dose schedule with Euvichol induces a strong vibriocidal response comparable to those elicited by the currently WHO prequalified OCV, Shanchol. Euvichol will be an oral cholera vaccine suitable for use in lower income countries, where cholera still has a significant economic and public health impact.