Pregnancy Outcomes after a Mass Vaccination Campaign with an Oral Cholera Vaccine in Guinea: A Retrospective Cohort Study

Abstract

IntroductionSince 2010, WHO has recommended oral cholera vaccines as an additional strategy for cholera control. During a cholera episode, pregnant women are at high risk of complications, and the risk of fetal death has been reported to be 2–36%. Due to a lack of safety data, pregnant women have been excluded from most cholera vaccination campaigns. In 2012, reactive campaigns using the bivalent killed whole-cell oral cholera vaccine (BivWC), included all people living in the targeted areas aged ≥1 year regardless of pregnancy status, were implemented in Guinea. We aimed to determine whether there was a difference in pregnancy outcomes between vaccinated and non-vaccinated pregnant women.Methods and FindingsFrom 11 November to 4 December 2013, we conducted a retrospective cohort study in Boffa prefecture among women who were pregnant in 2012 during or after the vaccination campaign. The primary outcome was pregnancy loss, as reported by the mother, and fetal malformations, after clinical examination. Primary exposure was the intake of the BivWC vaccine (Shanchol) during pregnancy, as determined by a vaccination card or oral history. We compared the risk of pregnancy loss between vaccinated and non-vaccinated women through binomial regression analysis. A total of 2,494 pregnancies were included in the analysis. The crude incidence of pregnancy loss was 3.7% (95%CI 2.7–4.8) for fetuses exposed to BivWC vaccine and 2.6% (0.7–4.5) for non-exposed fetuses. The incidence of malformation was 0.6% (0.1–1.0) and 1.2% (0.0–2.5) in BivWC-exposed and non-exposed fetuses, respectively. In both crude and adjusted analyses, fetal exposure to BivWC was not significantly associated with pregnancy loss (adjusted risk ratio (aRR = 1.09 [95%CI: 0.5–2.25], p = 0.818) or malformations (aRR = 0.50 [95%CI: 0.13–1.91], p = 0.314).ConclusionsIn this large retrospective cohort study, we found no association between fetal exposure to BivWC and risk of pregnancy loss or malformation. Despite the weaknesses of a retrospective design, we can conclude that if a risk exists, it is very low. Additional prospective studies are warranted to add to the evidence base on OCV use during pregnancy. Pregnant women are particularly vulnerable during cholera episodes and should be included in vaccination campaigns when the risk of cholera is high, such as during outbreaks.

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

“…Our data are also concordant with an analysis of pregnancy outcomes among women who received Shanchol while pregnant during a vaccine campaign in Guinea [6]. Similar findings were observed for the Dukoral™ cholera vaccine in Zanzibar [7].…”

“…The data that do exist show no evidence of a harmful effect. One recent study in Guinea showed that there was no significant increase in adverse fetal or newborn outcomes among pregnant women who received killed OCV [6]. Another study conducted in Zanzibar showed that there was no statistically significant evidence of a harmful effect of gestational exposure to a killed OCV [7].…”

Highlights of the 8th International Conference on Vaccines for Enteric Diseases: the Scottish Encounter To Defeat Diarrheal Diseases

“…Of 263 hospitalized pregnant women in Haiti, none died, but 21 (8%) suffered intrauterine fetal death, with the main risk factors being severe dehydration and vomiting. In Guinea, of 2,494 vaccinated women (ascertained by card or oral history) examined, no association between fetal exposure to OCV and risk of pregnancy loss or malformation was found (24). These results open the discussion for the inclusion of pregnant women in future vaccination campaigns, particularly during outbreaks or when risk of cholera infection is high.…”

“…Pregnant women are a high-risk group during cholera outbreaks, and while oral cholera vaccination has been recommended for other groups, expecting mothers have been excluded due to the lack of safety data. Lise Grout and colleagues from the European Programme for Intervention Epidemiology (EPIET), Sweden, the Ministry of Health and Public Hygiene, Guinea, and Médecins Sans Frontières reviewed pregnancy outcomes in women with cholera who were hospitalized during the 2010 -2011 outbreak in Haiti and investigated a retrospective cohort of women who were pregnant during or after the OCV campaign study in Guinea (24). Of 263 hospitalized pregnant women in Haiti, none died, but 21 (8%) suffered intrauterine fetal death, with the main risk factors being severe dehydration and vomiting.…”

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

“…In Tanzania, the risk of pregnancy loss was not significantly higher among pregnant women who were inadvertently vaccinated with Dukoral during the mass vaccination campaign in 2009 7 . Findings from a retrospective cohort study in Guinea showed no evidence of increased risk of pregnancy loss after receiving Shanchol 8 . However, such retrospective studies are subject to biases and represent low-quality evidence.…”