Killed Oral Cholera Vaccine Appears Safe in Pregnant Women

By Will Boggs MD

February 21, 2017

NEW YORK (Reuters Health) – The killed oral cholera vaccine appears to be safe in pregnant women, according to a small observational study in Malawi.

Although the World Health Organization (WHO) recommends vaccination of pregnant women in cholera-endemic settings, most vaccination campaigns exclude pregnant women because of insufficient safety data for use during pregnancy.

Dr. Mohammad Ali from Johns Hopkins Bloomberg School of Public Health in Baltimore, Maryland, and colleagues evaluated the pregnancy outcomes of 361 women who received the Shanchol killed oral cholera vaccine versus 327 women who lived in an adjacent community who were not vaccinated due to insufficient supplies of the vaccine.

About a quarter of women (27%) were exposed in their first trimester, 40% in their second trimester, and 33% during their third trimester, the researchers report in The Lancet Infectious Diseases, online February 1.

The overall rate of pregnancy loss did not differ significantly between vaccinated women (27.54 per 1,000 pregnancies) and non-vaccinated women (21.56 per 1000 pregnancies), and the risk of pregnancy loss after exposure to oral cholera vaccine was not significantly changed after controlling for other factors (p=0.52).

Neonatal mortality rates did not differ between the mothers exposed and not exposed to the vaccine, and the rates of stillbirth and spontaneous miscarriage were similar in the two groups.

Two newborns in the vaccine exposure group and one in the no-exposure group were considered to have malformations (p=0.57).

“Thus, on the basis of current understanding of the vaccine and evidence from our clinical studies, pregnant women should not be excluded from oral cholera vaccination during vaccine campaigns,” the researchers conclude. “They would be at high risk if they develop cholera and this risk can be lowered with oral cholera vaccine without clinically significant risk to the woman or her fetus.”

Dr. Pedro L. Moro from Centers for Disease Control and Prevention in Atlanta, Georgia, who coauthored an accompanying editorial, called the researchers’ findings “reassuring” in an email to Reuters Health.

“Their results are consistent with a previous study which used the same vaccine in pregnant women in Guinea and found no increased risk of fetal loss among women exposed to the vaccine,” he said.

“Cholera vaccines can be safely used during pregnancy, and should not be withheld from pregnant women in the setting of an outbreak or where the prevalence of cholera is high,” Dr. Moro said. “Future studies should include more pregnant women, especially women in the first trimester of pregnancy, to more fully evaluate early pregnancy loss, as well as other pregnancy (e.g. preterm delivery) and infant outcomes (e.g. birth defects).”

Dr. Firdausi Qadri from International Centre for Diarrhoeal Disease Research, Bangladesh, in Dhaka, who recently reported on immune responses in women with cholera, told Reuters Health by email, “Our results and those of others recently do show the safety of oral cholera vaccine in pregnant women who received it in large trials (without knowing they were pregnant at the time). Thus, this has provided evidence of the safety of the vaccine in pregnancy and also that it does not have any effect on fetal outcome.”

“Physicians need to understand that the vaccine is safe and can be given to pregnant women,” Dr. Qadri concluded. “In spite of being safe, a label change is needed for the vaccine. Companies have to come forward and make a clear recommendation and go for label change/clarification. However, that is not such an easy matter.”

The study was funded by the Bill and Melinda Gates Foundation. The authors declared no competing interests.

Dr. Ali did not respond to a request for comments.


Lancet Infect Dis 2017.


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