Immune responses following one and two doses of the reformulated, bivalent, killed, whole-cell, oral cholera vaccine among adults and children in Kolkata, India: A randomized, placebo-controlled trial

Antigen-Specific Memory B-Cell Responses in Bangladeshi Adults after One- or Two-Dose Oral Killed Cholera Vaccination and Comparison with Responses in Patients with Naturally Acquired Cholera

“…Cholera is caused by Vibrio cholerae O1 and O139, and it is estimated that 5 million cases of cholera occur each year, resulting in 100,000 deaths (40,42). Cholera can occur in explosive outbreaks, as evidenced by the outbreak beginning in 2008 in Zimbabwe that affected over 100,000 individuals and resulted in more than 4,000 deaths (15), as well as outbreaks in 2010 in Pakistan (39) and Haiti (10).…”

Vaccination against cholera in Juba – Authors' reply

“…Using the same method, we calculated the expected proportion of patients with cholera who were vaccinated to be 8%, not 36% as they calculated, compared with the 6% observed, suggesting that chronic HCV infection treated with both interferon-based 4 and interferonfree 5 direct-acting antiviral regimens. In the C-SWIFT study, 5 which assessed the efficacy of 6 weeks of grazoprevir/ elbasvir plus sofosbuvir in patients with non-cirrhotic HCV genotype 1 infection, the sustained virological response rate 12 weeks after the end of treatment was 69% (nine of 13) in patients with baseline HCV RNA greater than 2 000 000 IU/mL, and 100% (17 of 17) in those with baseline HCV RNA 2 000 000 IU/mL or lower.…”

“…This is not supported by current evidence: immunological data, observational studies, and clinical trials published to date support single-dose protection. [2][3][4] Estimates of short-term efficacy of one and two doses of OCV in south Asia are similar, suggesting that, at least in the short-term, one dose might provide similar protection to two doses. 3,5 Single-dose campaigns allow the vaccinated population to double, with fewer doses, which might improve the effect of reactive campaigns through direct and herd protection.…”

“…3 Efficacy of onedose OCV was estimated to be about 40% (95% CI 11-60) in a double-blind placebo-controlled clinical trial. 4 Using the WHO screening method 5 with provided data, we calculated that 36% of cholera cases were expected to occur in vaccinated individuals in Juba. The observed proportion was only 6%, 3 which suggests biases that the authors could not address despite their efforts to do so.…”

Achievements and challenges for the use of killed oral cholera vaccines in the global stockpile era

“…32 When comparing responses between one and 2 vaccine doses, investigators from Kolkata found no increase in seroconversion (4-fold rise in serum vibriocidal antibodies), following a second dose as compared to those after the first dose. 33 Interestingly, this may be directly related to the amount of natural exposure and pre-existing antibodies since higher seroconversion rates were noted following a second dose in comparatively less endemic areas in Haiti and Ethiopia. 29,34,35 This suggests that there may be important geographical differences in immunological response in areas of varying cholera exposure.…”