Recommended Interval for Anti-Rabies Vaccine Booster Doses
The recommended interval for anti-rabies vaccine booster doses depends on the person's risk category, with those at continuous risk requiring antibody testing every 6 months and those at frequent risk requiring testing every 2 years, with boosters administered when antibody titers fall below the protective level. 1
Risk-Based Booster Schedule
Continuous Risk Category
- Individuals who work with live rabies virus in research laboratories or vaccine production facilities are at highest risk of inapparent exposures 1
- These individuals should have serum tested for rabies antibody every 6 months 1
- Booster doses should be given when serum titer falls below complete neutralization at a 1:5 serum dilution by the Rapid Fluorescent Focus Inhibition Test (RFFIT) 1
Frequent Risk Category
- Includes laboratory workers doing rabies diagnostic testing, spelunkers, veterinarians and staff, animal-control and wildlife officers in areas where animal rabies is epizootic, and international travelers living in areas with endemic canine rabies for >30 days 1
- These individuals should have serum tested for rabies antibody every 2 years 1
- A booster dose is required if the titer is less than complete neutralization at a 1:5 serum dilution by RFFIT 1
- Alternatively, a booster can be administered in lieu of a titer determination 1
Infrequent Exposure Group
- Veterinarians and animal control/wildlife officers working in areas with low rabies enzooticity do not require routine preexposure booster doses after completing primary preexposure vaccination 1
Booster Effectiveness and Duration
- A single booster dose after primary vaccination confers a high and long-term immune response in nearly all individuals 2
- Studies show that after a booster dose, rabies antibody levels can remain above protective levels for up to 5 years in many individuals 3
- One study demonstrated that 68.6% of participants maintained adequate rabies virus neutralizing antibody concentrations (≥0.5 IU/mL) for up to 10 years without requiring a booster dose 4
Special Considerations
Previously Vaccinated Individuals Exposed to Rabies
- If exposed to rabies, previously vaccinated persons should receive two IM doses (1.0 mL each) of vaccine, one immediately and one 3 days later 1, 5
- Rabies immunoglobulin is unnecessary and should not be given in these cases 1, 5
Immunosuppressed Individuals
- Patients who are immunosuppressed by disease or medications should have their antibody titers checked after vaccination 1
- Failures to seroconvert after vaccination should be managed in consultation with appropriate public health officials 1
Antimalarial Medications
- Chloroquine phosphate interferes with the antibody response to HDCV when administered intradermally 1
- For persons receiving antimalarial prophylaxis, the intramuscular route for rabies vaccination is preferred 1
Monitoring Antibody Levels
- Antibody titers are used to monitor the relative rabies immune status over time among persons at higher than normal risk for exposure 1
- Two years after primary pre-exposure vaccination, 93%-98% of persons who received the 3-dose pre-exposure series intramuscularly and 83%-95% of persons who received the 3-dose series intradermally still showed complete neutralization of challenge virus at a dilution of 1:5 1
- Recent research suggests that a systematic booster after primary vaccination may reduce the need for frequent antibody monitoring in occupationally exposed individuals 2
Practical Approach to Booster Administration
- For continuous risk: Test antibody levels every 6 months and administer booster when titer falls below protective level 1
- For frequent risk: Test antibody levels every 2 years and administer booster when titer falls below protective level or give booster directly without testing 1
- For infrequent risk: No routine boosters required after primary vaccination series 1
- For post-exposure in previously vaccinated: Two doses on days 0 and 3, regardless of time since previous vaccination 5