Live cholera vaccine

Some of the views expressed in the following notes on newly approved products should be regarded as preliminary, as there may have been limited published data at the time of publication, and little experience in Australia of their safety or efficacy. However, the Editorial Executive Committee believes that comments made in good faith at an early stage may still be of value. Before new drugs are prescribed, the Committee believes it is important that more detailed information is obtained from the manufacturer's approved product information, a drug information centre or some other appropriate source.

Orochol (CSL)
Sachets containing 2–10 x 108 colony forming units of Vibrio cholerae
Approved indication: immunisation
Australian Medicines Handbook Section 20.1.2

Vaccines based on heat-killed suspensions of Vibrio cholerae are not very effective. The injectable vaccine is also associated with systemic adverse effects. A live vaccine given by mouth may have advantages.

The new product is a recombinant form of the bacteria with the deletion of the gene coding for part of the cholera toxin. This live strain is known as Vibrio cholerae CVD 103-HgR.

Adult volunteers took the vaccine and were then exposed to virulent Vibrio cholerae 8-180 days later. There was complete protection against cholera, if the bacteria were of the same serotype as the vaccine. This protection was present as early as eight days after vaccination.

People (including children more than two years old) who are at a high risk of infection when travelling through endemic areas can take the vaccine at least a week before travel. The single dose sachet has two sections. Their contents are mixed together in 100 mL of water then drunk. The traveller should not eat for an hour after taking the vaccine. Common adverse effects include abdominal pain, increased bowel sounds and headache.

Live oral cholera vaccine should be taken at least one week before starting chloroquine as the antimalarial drug can reduce the immune response. Oral typhoid vaccine and oral cholera vaccine should be given at least eight hours apart, as the cholera vaccine may affect the passage of the capsules, containing the typhoid vaccine, through the gut. If possible, vaccinees should avoid contact with immuno compromised people for eight days after taking the vaccine.

Although the vaccine protected the volunteers in the challenge studies, it was much less effective if the virulent bacteria were from a different serotype. There is also little published evidence yet of the vaccine's effectiveness in field trials. While 60-70% of people will seroconvert after vaccination, this may not reflect the intestinal antibody response or clinical effectiveness. Although a booster dose is recommended every six months the duration of immunity after a single dose is unknown. There is a Cochrane review of cholera vaccines but it currently contains no effectiveness data for this new product.1

References

  1. Graves P, Deeks J, Demicheli V, Pratt M, Jefferson T. Vaccines for preventing cholera (Cochrane Review). In: The Cochrane Library, Issue 3. Oxford: Update Software. 1999.