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Fighting Cholera With Mass Vaccination

The views expressed are those of the author and are not necessarily those of Scientific American.


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When studying bacteria it is quite easy to get fascinated with them as a laboratory specimen while forgetting the huge impact they can have in real life societies. I find the PLoS journal of Neglected Tropical diseases redresses that as it covers work with bacteria and parasites from the front line. My previous post from this journal was about how bacteria were stored and cultured in non-laboratory conditions, including in remote areas where bacterial infections can have the most impact. This time I’m looking at the challenges faced by the organisation of a mass vaccination scheme against the bacteria Vibrio cholerae.

Scanning electron microscope image of Vibrio cholerae bacteria, which infect the digestive system. Reference and credit link below.

The mass vaccination trial was carried out in selected villages in Odisha on the east coast of India. Two doses of the oral vaccine were offered to everyone over the age of 1 (but not pregnant women). The vaccine consists of killed cholera cells in contrast to previous vaccines which contained parts of cholera toxin. Odisha was chosen for the trial as it is highly prone to natural disasters such as floods and droughts creating conditions ideal for the spread of cholera.

Study area in Satyabadi block, Odisha, India. Image from reference 1.

After collaborating with health volunteers, health workers and community leaders, vaccination booths were set up in the areas chosen for the study such that no villager had to walk for more than 15 minutes to reach them. As there were no long-term storage facilities in the booths each one also had to be close enough to a central storage facility to ensure the vaccines could be carried there and back each day with an ice-pack.

Before the vaccinations were carried out, public health and awareness activities were undertaken within the community to ensure as many people as possible understood the importance of getting the vaccination. Local newspapers, posters, leaflets, banners, mobile announcements and a door-to-door announcement program by health volunteers were used to spread the information.

The vaccine coverage achieved by this campaign was 46–61%, lower than observed (59–83%) during previous studies of oral cholera vaccines. Adults were less likely to be vaccinated than children, which researchers speculated may be due to the opening times of the booths, and suggested that in future they could be open later in the evening, or earlier in the mornings before work. The current booths had to close at 5 pm as unused vaccine vials had to be sent back to a central storage facility. As there is already a Polio vaccination scheme in the area (available for young children) it may also be that vaccination is assumed to be a thing children need more than adults.

Women walking through the fields for vaccination. Image Credit: Ms Hyon Jin Jeon (the International Vaccine Institute staff)

Researchers also reported negative responses to the taste and smell of the vaccine. This, as well as hot humid weather during vaccinating days, may also have kept people away. The demographic least likely to be vaccinated was older males of high socio-economic status. Broken down by age the vaccination coverage was 62% for children aged 1–14 years and 41% for all 15+ years.

It’s fascination to understand the logistics of this kind of vaccination program – from working out optimal placement of vaccination booths for vaccine delivery and people visiting, to organising a limited pool of health workers and volunteers on vaccination days. Although this was a trial in specific villages the researchers point out that anyone who turned up from outside the study area was also given a vaccine, although their data was not included in the study. With such important health implications, it would have been unethical to refuse it!

Reference 1: Kar SK, Sah B, Patnaik B, Kim YH, Kerketta AS, et al. (2014) Mass Vaccination with a New, Less Expensive Oral Cholera Vaccine Using Public Health Infrastructure in India: The Odisha Model. PLoS Negl Trop Dis 8(2): e2629. doi:10.1371/journal.pntd.0002629

Image 1 reference: T.J. Kirn, M.J. Lafferty, C.M.P Sandoe and R.K. Taylor, 2000, “Delineation of pilin domains required for bacterial association into microcolonies and intestinal colonization”, Molecular Microbiology, Vol. 35(4):896-910

S.E. Gould About the Author: A biochemist with a love of microbiology, the Lab Rat enjoys exploring, reading about and writing about bacteria. Having finally managed to tear herself away from university, she now works for a small company in Cambridge where she turns data into manageable words and awesome graphs. Follow on Twitter @labratting.

The views expressed are those of the author and are not necessarily those of Scientific American.





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