31 May 2006

 

A review of oral cholera vaccines: use in clinical practice

Professor David Hill, Dr. Lisa Ford and Dr. David Lalloo have published a review of oral cholera vaccines in the June issue of the journal Lancet Infectious Diseases [1].  The review focuses on Dukoral and its role in the prevention of cholera and enterotoxigenic Escherichia coli (ETEC), a common cause of travellers’ diarrhoea.  The vaccine comprises four strains of Vibrio cholerae O1, plus the recombinant B subunit of cholera toxin.  Because cholera toxin is very similar to the heat-labile (LT) toxin of ETEC, the vaccine has been studied for its ability to prevent this agent as well as V. cholerae. Dukoral is made by SBL Vaccin AB, Sweden, and is marketed in the UK by Chiron Vaccines.  It was approved by the European Union in 2004 for use against cholera.

The findings of the review are summarised as follows:

Use of Dukoral in Cholera

• Dukoral is well tolerated. Most side effects are limited to mild gastrointestinal events.
• Vaccines that combine killed V. cholerae plus the B subunit of cholera toxin demonstrate good protective efficacy against V. cholerae 01 for 4 to 6 months in persons living in endemic countries (range 61%-86% protection).  In children aged 2 to 5 years, protection wanes rapidly after 6 months. There is no protection against infection against another cause of cholera, V. cholerae O139.
• The risk of cholera can be estimated to be 2 to 3 imported cases per million travellers to 1 to 4 cases per 10,000 persons when enhanced surveillance or expatriate populations are included.
• Vaccination against cholera can be considered for the following categories of travellers (in the absence of specific data).
  • Relief and disaster workers in cholera-endemic countries
  • Persons with remote itineraries in areas where cholera epidemics are occurring and there is limited access to medical care
• Using available resources to document cholera outbreaks, it is key to make an individual risk assessment based on the traveller’s underlying health, the destination and duration of travel, and planned activities.

Use of Dukoral in ETEC and Travellers’ Diarrhoea

• The contribution of LT-producing E. coli in travellers’ diarrhoea is variable and often small. Recent data demonstrates that a median of 21% of travellers’ diarrhoea stool samples are positive for ETEC; the percent of LT-producing E. coli ranges from 6% to 10%.
• Vaccination with Dukoral provides moderate cross protection of 60% to 67% against LT-producing E. coli over 3 months.
• There is evidence in travellers of a low protective efficacy of Dukoral against the syndrome of travellers’ diarrhoea.
• Based on estimates of the incidence of travellers’ diarrhoea, the prevalence of LT-producing E. coli and the protective efficacy of the vaccine, Dukoral can be expected to protect 7% or less of travellers against travellers’ diarrhoea.
• In general, the rCTB-WC vaccine should not be used for the prevention of travellers’ diarrhoea.

Vaccination with Dukoral does not preclude exercising care with food and drink selection during travel.

Reference

1. Hill DR, Ford L, Lalloo D.  Oral cholera vaccines: use in clinical practice.  Lancet Infect Dis  2006;6:361-73.

Link

Summary of Product Characteristics. Dukoral Oral Cholera Vaccine. SBL Vaccine AB, Stockholm Sweden. Available at: http://emc.medicines.org.uk/emc/industry/default.asp?

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