What is the chance of getting rabies after receiving Post-Exposure Prophylaxis (PEP) and the rabies vaccine?

Effectiveness of Rabies Post-Exposure Prophylaxis

Properly administered rabies post-exposure prophylaxis (PEP) is virtually 100% effective in preventing rabies when given promptly and appropriately, with breakthrough infections being exceedingly rare. 1, 2

Understanding PEP Effectiveness

Rabies PEP is one of the most successful medical interventions available when properly administered. The Advisory Committee on Immunization Practices (ACIP) notes that observational studies indicate PEP is universally effective in preventing human rabies when administered promptly and according to guidelines 1.

Key points about PEP effectiveness:

• All healthy persons develop detectable rabies virus-neutralizing antibodies by day 14 after initiation of PEP 1
• Of the >55,000 people who die annually of rabies worldwide, the majority either:
  • Did not receive any PEP
  • Received PEP after substantial delays
  • Received PEP that deviated significantly from recommended protocols 1

Documented PEP Failures

While extremely rare, breakthrough infections (rabies occurring despite PEP) have been documented:

• A systematic review identified only 122 breakthrough infections in the literature between 1980 and 2022 3
• Of these cases, 56% had documented deviations from core practices (proper wound cleaning and vaccine administration) 3
• Most breakthrough cases involved severe wounds (69%), particularly multiple wound sites or bites to the head, face, or neck 3
• The median time from exposure to symptom onset in breakthrough cases was only 20 days 3

Factors Associated with PEP Failure

When PEP failures occur, they are typically associated with:

1. Deviations from recommended protocols, including:

   • Improper wound cleansing
   • Failure to infiltrate rabies immunoglobulin around the wound
   • Administering vaccine in the gluteal area instead of the deltoid 1
   • Failure to complete the full vaccination course 4

2. High-risk exposures:

   • Severe wounds, especially to head, face or neck
   • Multiple bite wounds
   • Short incubation period cases 5

3. Patient factors:

   • Immunosuppression or comorbidities 3
   • Delays in seeking healthcare 3

Ensuring Optimal Protection

To maximize PEP effectiveness:

• Immediate wound cleansing with soap and water for at least 15 minutes is critical 2, 6
• Rabies immune globulin must be properly infiltrated around the wound 6
• Vaccine administration must follow the correct schedule and be given in the deltoid (never gluteal) area 2
• Complete the full course of vaccination (4 doses for immunocompetent individuals, 5 doses for immunocompromised) 2

Conclusion

The risk of developing rabies after receiving proper PEP is extraordinarily low. The CDC and WHO data confirm that when administered correctly and promptly, modern rabies PEP is nearly 100% effective. The few documented failures almost always involve protocol deviations or extremely high-risk exposures.

For anyone concerned about potential rabies exposure, immediate medical attention is essential, as PEP is highly effective when started promptly, but rabies is almost universally fatal once symptoms develop.