This evening, I enjoyed catching up with a medical school friend who works extensively in Haiti. Upon returning home I found an issue of the Journal of Infectious Diseases in my mailbox. Opening it up, I discovered an article written by several of my colleagues from Mass General/ Brigham about the oral cholera vaccine in adults with HIV infection in Haiti. Caveats regarding this blog post: I don’t claim to know much about cholera and I haven’t spoken with any of my Mass General/Brigham colleagues regarding this study.
This study is important because cholera often occurs in parts of the world where there is a high burden of HIV. For example, in Beira, Mozambique (about an hour flight north from Maputo), there was cholera in 2005-2006 and a research paper suggested that HIV infection was associated with an increased risk for cholera. Thankfully there were no outbreaks of cholera in Mozambique when I worked/lived there (2011-2012), but it was always a consideration when a patient came into the hospital with profuse diarrhea. Even though more and more people with HIV are getting on lifesaving antiretroviral therapy in Mozambique and around the world, the burden of HIV remains enormous. Cholera transmission is ongoing in many of these settings so individuals with HIV remain at risk. Now, lets journey to Haiti.
Louise Ivers and colleagues studied Haitian individuals with HIV who had received the bivalent oral cholera vaccine BivWC which is marketed as “Shanchol.” This is a killed whole-cell bacterial vaccine. Since the Haiti earthquake and subsequent cholera epidemic, the Haitian Ministry of Health has rolled out the BivWC vaccine in an attempt to reduce cholera transmission. In St. Marc, Haiti adults with HIV infection received the vaccine and their serum was shipped to Boston for immunological analysis. In this paper, the researchers studied 25 adults with HIV who received BivWC. The median CD4 count of these patients was 433. All but two were on ART and the two who were not on ART had CD4 counts above 500. The researchers found that adults with HIV had a decreased vibriocidal antibody response to the BivWC vaccine, especially for patients with the lowest CD4 counts. However, the majority of HIV-infected individuals still did have seroconversion to the vaccine.
Ivers and colleagues comment on the small sample size and the fact that vibriocidal antibodies are not likely to directly mediate protection from cholera, so their study does not definitively address the question of vaccine efficacy in HIV infected individuals. That makes sense. My main question for the researchers would be about the CD4 cell counts. In many parts of Sub-Saharan Africa where cholera transmission occurs and there is a high prevalence of HIV (I am thinking of Beira, Mozambique for example), there remain many people who are not on ART. People with AIDS are at high risk for opportunistic infections and diseases like cholera because of their advanced immunosuppression. Practically speaking, human resources are limited in such settings (overloaded clinics, lack of nurses, etc) but cholera transmission must be avoided at all costs. Is there enough evidence to roll out the BivWC vaccine widely in such settings? The authors comment that additional doses of vaccine might need to be given to people with low CD4 counts. What kind of studies would be needed to investigate this question?
Thanks to the power of Twitter, Louise Ivers already wrote back. She said, “vaccine safe, and reasonable seroconversion in HIV but need bigger study w/ lower cd4 counts. Vaccine also in v short supply”