A Q&A with Dr David Sack on the History of Oral Cholera Vaccine (Part 3 of 3)
Previous research has shown the safety and immunogenicity of oral cholera vaccine (OCV) at elevated temperatures in vaccinated individuals. These findings suggest that hard to reach populations with endemic cholera have the ability to be vaccinated with limited cold chain capacity because larger doses of the vaccine can be transported without the constraints of being transported with heavy volumes of ice-packs. Listen to the audio below or read the transcripts to hear Dr. Sack share further insight into the vaccine cold chain and challenges of maintaining the vaccine at elevated temperatures.
Dr. Sack recently appeared as a guest lecturer for the online course, Current Issues in Public Health, at the Johns Hopkins Bloomberg School of Public Health. As part of the course, students had the opportunity to submit questions for Dr. Sack online.The audio and transcripts below capture the conversation between Dr. David Sack, Dr. Edyth Schoenrich, and the Teaching Assistant as Dr. Sack answers students’ questions.
Q: One thing that actually surprised me too was that this [the vaccine] is actually a treatment that needs to be kept cold. How much is that a barrier to getting it out to these [remote] areas versus just the normal travel times?
David Sack: Of course [the vaccine] needs to be provided to people who are living in remote areas where it’s going to be difficult to maintain a cold chain but I think perhaps the thinking was, well this is a vaccine and all vaccines need to be kept cold, so if other vaccines are cold, this one can just be kept cold also. The problem with that thinking is that this vaccine is not delivered through the normal EPI channels like the other childhood vaccines. So it was frustrating since we have pretty good information that the vaccine does not really need to be kept cold, that because of the way it’s registered and the agency has to look at the package insert and follow the instructions they would feel like they’d be blamed if they didn’t do it according to the package insert.
Q: So you were talking about resources and I think that brings us to some other questions in terms of health inequities and the poorest being at the highest risk and I was wondering if you could talk a little more about that – how is that showing?
DS:Within a community, the people who get cholera and particularly the people who die of cholera are certainly the ones who are the most vulnerable - the poorest of the poor. Frequently these are people who don’t have connections. We talk about access to care being important. People need connections. How do you actually know where to go if you’re sick? The most vulnerable may not even understand what the disease is or where they could go or even if they have the right to go seek treatment. Then the most vulnerable are those are those that live in very remote areas where there is no treatment available.
Q: Do you, in your experience, find that people are ignoring [the knowledge about the cold chain vaccines] knowing that it’s still efficacious if not kept cold or do they have to be pretty strict about it?
DS: Well, some have been very strict; MSF is much wiser than some of the others – they’ve bent the rules a little bit in the sense that they keep it cold until the day of the vaccine delivery. So at the central storage, it’s cold but then when they go into the field, they just put it in a normal box and take it and then at the end of the day if they have some left over, they bring it back, put it back into the cold, and then use those doses first thing the next day. There’s a whole science around the cold chain and this vaccine has what’s called a VVM 14, which theoretically means it could be kept at room temperature for 14 days. The VVM is the vaccine vial monitor which turns color if it's been exposed to too much heat. Q: Are people trying to overturn this? A: We’re trying to get it re-labeled as a VVM 30 and what that would allow us to do would be to allow community health workers to take the vaccine and deliver it to the communities and then it could be outside the cold chain for 2-3 weeks. I think that would make a huge difference to how convenient it is and getting back to the equity issue, I think we’d also reach the people who need to be reached.
Dr. David Sack, M.D, is a professor of International Health at the Johns Hopkins Bloomberg School of Public Health. He has spent his career devoted to the control of infectious diarrheal diseases like cholera, rotavirus, and diarrhea due to enterotoxigenic E. coli. In addition to directing the Delivering Oral Vaccine Effectively (DOVE) project, he is also head of the Enteric Laboratory at the Johns Hopkins University Center for Immunization Research, which carries out clinical trials of new enteric vaccines.