Rabies Vaccines
Introduction to Rabies Vaccines
Rabies vaccines are biologics used to prevent rabies, a fatal viral disease that affects the central nervous system. Rabies is caused by viruses in the genus Lyssavirus and is typically transmitted through the bite of an infected animal.
Key Points:
- Rabies vaccines can be used for both pre-exposure prophylaxis (PrEP) and post-exposure prophylaxis (PEP).
- Modern rabies vaccines are cell-culture based and are considered highly effective and safe.
- The first rabies vaccine was developed by Louis Pasteur in 1885, using dried nerve tissue from rabies-infected rabbits.
- Current vaccines are inactivated (killed) virus vaccines, eliminating the risk of vaccine-induced rabies.
- Rabies vaccination is often used in conjunction with Rabies Immunoglobulin (RIG) for post-exposure treatment.
Types of Rabies Vaccines
Modern rabies vaccines are all cell culture-based or embryonated egg-based vaccines. The main types include:
1. Human Diploid Cell Vaccine (HDCV)
- Produced using human diploid cell culture
- Brand name: Imovax Rabies
- High immunogenicity and safety profile
2. Purified Chick Embryo Cell Vaccine (PCECV)
- Produced using primary chicken fibroblasts
- Brand name: RabAvert
- Comparable efficacy to HDCV
3. Purified Vero Cell Rabies Vaccine (PVRV)
- Produced using Vero cells (African green monkey kidney cells)
- Widely used in many countries, especially in Asia
- Not licensed in the United States
4. Primary Hamster Kidney Cell Vaccine
- Used in some countries, but not widely available
- Not recommended by WHO for production of new vaccines
Historical Vaccines (No Longer Recommended)
- Nerve Tissue Vaccines: First-generation vaccines, now discontinued due to severe adverse reactions
- Duck Embryo Vaccine: Second-generation vaccine, less effective than modern cell culture vaccines
Vaccine Efficacy
Rabies vaccines are highly effective when used correctly for both pre-exposure prophylaxis (PrEP) and post-exposure prophylaxis (PEP).
Pre-Exposure Prophylaxis (PrEP):
- Nearly 100% effective in producing adequate antibody titers
- Provides protection against all known rabies virus variants
- Simplifies post-exposure management if exposure occurs
Post-Exposure Prophylaxis (PEP):
- When administered promptly and properly, PEP is nearly 100% effective in preventing rabies
- Efficacy depends on timely administration and adherence to the recommended schedule
- Combination with Rabies Immunoglobulin (RIG) enhances efficacy for severe exposures
Duration of Protection:
- PrEP: Protective antibody levels typically persist for at least 2 years
- Booster doses can extend protection for those at continued risk
- After PEP, long-lasting immunity is generally achieved
Factors Affecting Efficacy:
- Timing of vaccination (especially crucial for PEP)
- Proper administration technique
- Patient's immune status
- Concurrent use of immunosuppressive drugs
Vaccination Schedule
Rabies vaccination schedules differ for pre-exposure prophylaxis (PrEP) and post-exposure prophylaxis (PEP). The World Health Organization (WHO) and the U.S. Centers for Disease Control and Prevention (CDC) provide guidelines:
Pre-Exposure Prophylaxis (PrEP):
- Primary series: 2 doses, given on days 0 and 7
- Route: Intramuscular (IM) or intradermal (ID)
- Booster: Generally not needed for general population; may be considered for high-risk individuals based on antibody titers
Post-Exposure Prophylaxis (PEP) for Previously Unvaccinated Individuals:
- 4-dose regimen: Doses on days 0, 3, 7, and 14
- Rabies Immunoglobulin (RIG) should be administered with the first dose
- Route: Intramuscular (IM)
Post-Exposure Prophylaxis (PEP) for Previously Vaccinated Individuals:
- 2-dose regimen: Doses on days 0 and 3
- RIG is not necessary
Special Considerations:
- Immunocompromised individuals may require a 5-dose PEP regimen (days 0, 3, 7, 14, and 28) plus RIG
- Intradermal vaccination schedules are used in some countries to reduce cost and extend vaccine supply
- Deviations from recommended schedules should be avoided whenever possible
Side Effects and Safety
Modern rabies vaccines are generally safe and well-tolerated, but like all medical interventions, they can cause side effects.
Common Side Effects:
- Local reactions: Pain, erythema, swelling, or itching at the injection site
- Systemic reactions: Headache, nausea, abdominal pain, muscle aches, dizziness
- Mild fever
Rare Side Effects:
- Severe allergic reactions (anaphylaxis): Extremely rare, estimated at 1 per 10,000 vaccinations
- Neurological complications: Very rare, including Guillain-Barré syndrome
Safety Considerations:
- No risk of rabies infection from the vaccine as it contains inactivated virus
- Safe for use in pregnancy and lactation when indicated
- Can be administered to immunocompromised individuals, though efficacy may be reduced
Contraindications and Precautions:
- Severe allergic reaction to a previous dose or vaccine component
- For pre-exposure prophylaxis, acute febrile illness may warrant postponement
- No absolute contraindications for post-exposure prophylaxis due to the fatal nature of rabies
Monitoring and Reporting:
Adverse events should be reported to appropriate national vaccine safety surveillance systems (e.g., VAERS in the United States).
Public Health Impact
Rabies vaccines have played a crucial role in controlling human rabies cases worldwide, particularly when combined with other preventive measures.
Global Impact:
- Dramatic reduction in human rabies cases in countries with comprehensive vaccination programs
- Elimination of dog-mediated rabies in many developed countries
- Significant decrease in rabies-related deaths in areas implementing mass dog vaccination
Challenges:
- High cost of vaccines and immunoglobulin, limiting access in resource-poor settings
- Lack of awareness about rabies and the importance of PEP in some regions
- Inadequate surveillance and reporting systems in many countries
- Continued presence of rabies in wildlife reservoirs
Strategies for Rabies Elimination:
- Mass dog vaccination campaigns in endemic areas
- Improved access to PEP for exposed individuals
- Enhanced surveillance and reporting systems
- Public education about rabies prevention and the importance of seeking PEP after potential exposures
One Health Approach:
Collaboration between human health, animal health, and environmental sectors is crucial for effective rabies control and elimination.
Economic Impact:
- Rabies vaccination programs are cost-effective, especially when compared to the economic burden of human rabies cases
- Intradermal vaccination has improved cost-effectiveness in some settings
Future Directions:
- Development of more thermostable vaccines for use in remote areas
- Research into novel vaccination strategies, including oral vaccines for wildlife
- Efforts to achieve the WHO goal of zero human deaths from dog-mediated rabies by 2030
Rabies Vaccines
- Q: What type of virus causes rabies? A: Lyssavirus
- Q: How is the rabies vaccine typically administered for pre-exposure prophylaxis? A: Intramuscular injection
- Q: How many doses are required for pre-exposure rabies vaccination? A: 3 doses
- Q: What is the typical schedule for pre-exposure rabies vaccination? A: Days 0, 7, and 21 or 28
- Q: How long does immunity from pre-exposure rabies vaccination typically last? A: At least 10 years
- Q: What additional treatment is required along with the rabies vaccine for post-exposure prophylaxis? A: Rabies immunoglobulin (RIG)
- Q: How many doses of rabies vaccine are typically given for post-exposure prophylaxis? A: 4 doses
- Q: What is the typical schedule for post-exposure rabies vaccination? A: Days 0, 3, 7, and 14
- Q: In which year was the first rabies vaccine developed by Louis Pasteur? A: 1885
- Q: What is the name of the modern cell culture-based rabies vaccine? A: Human diploid cell vaccine (HDCV)
- Q: What is the typical incubation period for rabies in humans? A: 1-3 months
- Q: What is the fatality rate for symptomatic rabies infections? A: Nearly 100%
- Q: Which animal is responsible for the majority of human rabies deaths globally? A: Dogs
- Q: What is the minimum age for receiving pre-exposure rabies vaccination? A: No minimum age (can be given to infants)
- Q: What is the storage temperature requirement for most rabies vaccines? A: 2-8°C (35-46°F)
- Q: Which organ system does the rabies virus primarily affect? A: Central nervous system
- Q: What is the typical dosage of rabies vaccine for both pre- and post-exposure prophylaxis? A: 1.0 mL
- Q: How quickly after a potential rabies exposure should post-exposure prophylaxis begin? A: As soon as possible (ideally within 24 hours)
- Q: What is the name of the rabies vaccine derived from purified duck embryo cells? A: Purified duck embryo vaccine (PDEV)
- Q: In what year did the WHO set the goal to achieve zero human deaths from dog-mediated rabies by 2030? A: 2015
- Q: What is the term for the fear of water associated with symptomatic rabies infection? A: Hydrophobia
- Q: How long can the rabies virus survive in the environment outside a host? A: It is quickly inactivated by sunlight and drying
- Q: What percentage of rabies cases occur in rural areas? A: Approximately 80%
- Q: In which continent does the highest number of human rabies deaths occur annually? A: Asia
- Q: What is the name of the less expensive alternative to human rabies immunoglobulin derived from horse serum? A: Equine rabies immunoglobulin (ERIG)
- Q: What is the recommended site for rabies vaccine administration in adults? A: Deltoid muscle
- Q: What is the recommended site for rabies vaccine administration in young children? A: Anterolateral thigh
- Q: How many countries were declared free of dog-mediated rabies as of 2021? A: Approximately 40
- Q: What is the name of the only known case of human survival from symptomatic rabies without intensive care? A: Jeanna Giese (2004 Milwaukee Protocol)
- Q: What is the typical time frame for antibody detection after rabies vaccination? A: 7-14 days
