Cholera vaccines are biological preparations designed to protect against cholera, an acute diarrheal infection caused by ingestion of food or water contaminated with the bacterium Vibrio cholerae. Cholera can lead to severe dehydration and death if left untreated.
Key Points:
Cholera vaccines are an important tool in cholera control, especially in endemic areas and during outbreaks.
They are used alongside other preventive measures such as improved sanitation and access to clean water.
The first cholera vaccine was developed in 1885 by Jaime Ferrán, a Spanish physician.
Modern cholera vaccines are much safer and more effective than early versions.
The World Health Organization (WHO) recommends the use of cholera vaccines in conjunction with other cholera prevention and control strategies.
Types of Cholera Vaccines
There are several types of cholera vaccines available, with oral vaccines being the most commonly used today:
1. Oral Cholera Vaccines (OCVs)
a. Dukoral (WC-rBS)
Contains killed whole cells of V. cholerae O1 and recombinant cholera toxin B subunit
Provides protection against V. cholerae O1
Licensed for use in individuals 2 years and older
b. Shanchol, Euvichol, and Euvichol-Plus
Contain killed whole cells of V. cholerae O1 and O139
Do not contain the cholera toxin B subunit
Licensed for use in individuals 1 year and older
c. Vaxchora
Live attenuated single-dose vaccine
Contains live attenuated V. cholerae O1 strain CVD 103-HgR
Licensed in the United States for adults 18-64 years old traveling to cholera-affected areas
2. Injectable Cholera Vaccines
Older type of cholera vaccine
No longer recommended by WHO due to limited efficacy and short duration of protection
Not commonly used today
Vaccine Efficacy
The efficacy of cholera vaccines varies depending on the type of vaccine and the population in which it's used.
Oral Cholera Vaccines (OCVs):
Dukoral (WC-rBS):
Provides about 85% protection in the first 6 months after vaccination
Protection drops to about 50-60% after 2 years
May provide some cross-protection against enterotoxigenic Escherichia coli (ETEC)
Shanchol, Euvichol, and Euvichol-Plus:
Provide about 65% protection in the first year after vaccination
Protection remains around 50% in the second year
Some studies suggest protection may last up to 5 years
Vaxchora:
Provides 90% protection at 10 days post-vaccination
Protection drops to about 80% at 3 months post-vaccination
Factors Affecting Efficacy:
Age: Lower efficacy in young children
HIV status: May be less effective in HIV-positive individuals
Malnutrition: Can reduce vaccine efficacy
Previous exposure to cholera: May enhance vaccine-induced immunity
Herd Immunity:
OCVs have shown to provide indirect protection to unvaccinated individuals in communities with high vaccination coverage, demonstrating a herd immunity effect.
Vaccination Schedule
The vaccination schedule varies depending on the type of cholera vaccine used:
Dukoral (WC-rBS):
Adults and children ≥6 years: 2 doses given orally 1-6 weeks apart
Children 2-5 years: 3 doses given orally 1-6 weeks apart
Booster: After 2 years for adults and children ≥6 years, after 6 months for children 2-5 years
Shanchol, Euvichol, and Euvichol-Plus:
All ages ≥1 year: 2 doses given orally 14 days apart
Booster: After 2 years
Vaxchora:
Single oral dose for adults 18-64 years
Should be administered at least 10 days before potential exposure to cholera
Special Considerations:
In outbreak settings, a single-dose strategy may be used with Shanchol or Euvichol to quickly provide short-term protection
Pregnancy: OCVs are considered safe for pregnant women
Immunocompromised individuals: OCVs are considered safe but may be less effective
Side Effects and Safety
Cholera vaccines are generally considered safe, with most side effects being mild and transient.
Common Side Effects:
Gastrointestinal discomfort
Abdominal pain
Diarrhea
Nausea
Vomiting (rare)
Headache
Fever (low-grade)
Rare Side Effects:
Severe allergic reactions (anaphylaxis): Extremely rare
OCVs do not contain live bacteria and cannot cause cholera
Safe for use in HIV-positive individuals, though efficacy may be reduced
Can be given to pregnant and breastfeeding women when indicated
Contraindications:
Severe allergic reaction to a previous dose or any vaccine component
Acute gastrointestinal illness or fever (vaccination should be delayed)
Precautions:
Immunocompromised individuals may have a reduced immune response
Dukoral: Avoid food and drink 1 hour before and after vaccination
Public Health Impact
Cholera vaccines have become an important tool in cholera control and prevention, particularly in endemic areas and during outbreaks.
Impact on Disease Burden:
Significant reduction in cholera cases in areas with high vaccination coverage
Effective in outbreak control when combined with other interventions
Provides protection to high-risk populations in endemic areas
Cost-Effectiveness:
OCVs have been shown to be cost-effective in various settings
Particularly cost-effective when used in targeted vaccination campaigns
Global Stockpile:
WHO manages a global OCV stockpile for outbreak response and emergency use
Has facilitated rapid response to cholera outbreaks in multiple countries
Challenges:
Limited global production capacity
Cold chain requirements for vaccine storage and distribution
Need for multiple doses for full protection with most OCVs
Vaccination alone is not sufficient; must be combined with improvements in water, sanitation, and hygiene
Future Directions:
Development of more thermostable vaccines
Research into single-dose vaccines for rapid outbreak response
Integration of OCV into routine immunization programs in high-risk areas
Improved surveillance and early warning systems for cholera outbreaks
Global Goals:
The Global Task Force on Cholera Control has set a goal to reduce cholera deaths by 90% by 2030, with OCVs playing a crucial role in this strategy.
Cholera Vaccines
What is cholera?
An acute diarrheal illness caused by infection with Vibrio cholerae bacteria
How many types of cholera vaccines are currently available?
Two main types: oral cholera vaccines (OCVs) and injectable vaccines
Which oral cholera vaccines are prequalified by the WHO?
Dukoral, Shanchol, Euvichol, and Euvichol-Plus
What is the composition of most oral cholera vaccines?
Killed whole-cell V. cholerae O1, with or without V. cholerae O139
How is Dukoral different from other oral cholera vaccines?
It contains recombinant cholera toxin B subunit in addition to killed whole cells
What is the recommended dosing schedule for most oral cholera vaccines?
Two doses given 1-6 weeks apart
At what age can oral cholera vaccines be given?
From 1 year of age and older, depending on the specific vaccine
How long does protection last after cholera vaccination?
Typically 3-5 years, with some vaccines providing shorter duration of protection
What is the efficacy of oral cholera vaccines?
About 65-85% protection in the first 6 months after vaccination
Are cholera vaccines recommended for routine use in all countries?
No, they are primarily recommended in cholera-endemic areas or during outbreaks
What is the role of cholera vaccines in outbreak control?
Can be used as part of a comprehensive control strategy, along with water and sanitation improvements
Can cholera vaccines be given to pregnant women?
Yes, the killed oral cholera vaccines are considered safe in pregnancy
What is the global stockpile of oral cholera vaccines used for?
For emergency response to outbreaks and in humanitarian crises
Are cholera vaccines 100% effective in preventing cholera?
No, they provide significant but not complete protection
What are the main advantages of oral cholera vaccines?
Easy to administer, good safety profile, and can induce herd immunity
Can cholera vaccines be used in HIV-positive individuals?
Yes, but the immune response may be lower than in HIV-negative individuals
What is the role of cholera vaccination in travelers?
Recommended for travelers to high-risk areas, especially aid workers
How quickly does protection develop after cholera vaccination?
Usually within 7-10 days after completing the vaccination course
Are there any contraindications for oral cholera vaccines?
Severe allergic reaction to previous dose or any vaccine component
What is the storage requirement for most oral cholera vaccines?
2-8°C (refrigerator temperature), should not be frozen
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