Cholera Vaccines May Not Fully Protect Children against Deadly Diarrheal Disease

While adults immunized against cholera may be well-protected, children who receive the same vaccines may be not be, according to a review conducted by researchers at Johns Hopkins Bloomberg School of Public Health. The findings – which were published in the journal, The Lancet Infectious Diseases – are concerning, considering that children under the age of five face a higher risk of dying from diarrheal diseases like cholera.

The researchers conducted a review of seven clinical trials and six observational studies focused on assessing the effectiveness of available cholera vaccines. They found that adults who received two doses of the standard cholera vaccine had a 58 percent reduced risk of contracting the infectious disease. In contrast, children under five who received the same vaccine reduced their risk by just 30 percent.

The review comes in the wake of a major cholera epidemic in Yemen, which started in April of this year. It’s estimated that 400,000 people have contracted the infection, with up to 1,900 cholera-associated deaths so far.

Cholera tends to affect developing countries without sanitation and water treatment facilities, preventing people from getting access to clean drinking water. The disease is often transmitted through water contaminated with fecal matter.

While oral vaccines for cholera have been available for decades, the researchers say that they have been underused due in part to the perception that they are ineffective. “There continues to be a lot of misinformation on what this vaccine is and what it can do,” said Dr. Andrew Azman, research associate in the Department of Epidemiology at the Bloomberg School.

Azman and his colleagues performed a review and meta-analysis of studies assessing the effectiveness of these cholera vaccines in both controlled clinical settings and real-world outbreak situations. In all, 500,000 participants took part in the 13 studies reviewed by the research team.

In light of their findings, Azman and his team believe this study could help inform future use of these oral cholera vaccines in both adults and children. Epidemiologists could develop a modified vaccine regimen to strengthen its protective effects in young children.

Alternatively, vaccine policy experts may advise parents in epidemic regions to make sure they are vaccinated to prevent children from being exposed to the disease in their household. As the study also found that a one dose regimen could be as effective as two doses of the vaccine, it could allow governments to vaccinate more people during an outbreak.