What protection does administering antibodies (immunoglobulins) provide to dogs?

Protection Provided by Antibody Injection in Dogs

Administering antibodies (rabies immune globulin) to dogs provides immediate, short-term passive protection against rabies infection, particularly when combined with vaccination, achieving nearly complete protection in experimental studies. 1

Mechanism and Duration of Protection

Antibody injections provide passive immunity that works through different mechanisms than vaccination:

• Immediate protection: Antibodies provide rapid protection without requiring the 7-10 days needed for active immunity to develop after vaccination 1
• Short duration: The protective effect persists only briefly, with a half-life of approximately 21 days 1
• No immunological memory: Unlike vaccines, passive antibody administration does not establish long-term immunity or memory response 1

Evidence of Effectiveness in Dogs

The most compelling evidence comes from a 1989 experimental study specifically evaluating postexposure prophylaxis in dogs:

• The combination of antibody serum and vaccine provided nearly complete protection compared to animals receiving vaccine only or no treatment 1
• This demonstrates that passive antibodies significantly enhance survival when administered alongside active vaccination 1

Clinical Applications

Passive immunization with antibodies is primarily used in two scenarios for dogs:

Prophylactic Use

• Immediate protection for puppies that failed to receive adequate maternal antibodies through colostrum 2
• Acute exposure risk: When there is immediate threat of acquiring infectious disease before active immunity can develop 2

Therapeutic Use

• Limited evidence exists for therapeutic applications in dogs 2
• Positive effects have been reported in dogs with distemper, though controlled studies are limited 2

Important Limitations and Caveats

Critical pitfall: Antibody preparations alone provide poor protection (63-88% mortality in experimental studies) and must be combined with vaccination for optimal outcomes 1

Additional considerations:

• Cost and availability: Passive immunization requires relatively low-cost, highly efficient immunoglobulin products to be practical in veterinary medicine 3
• Not a replacement for vaccination: Antibodies do not provide the long-lasting protection that active immunization achieves 3
• Interference with vaccines: High levels of maternal or administered antibodies can neutralize vaccine antigens, particularly with live vaccines, potentially interfering with development of active immunity 4

Comparison to Active Vaccination

Active vaccination in dogs provides superior long-term protection:

• Duration: Vaccines provide immunity lasting minimum 3 years for core diseases like distemper, parvovirus, and adenovirus 5
• Immunological memory: Vaccination establishes lasting immune memory 1
• Antibody production: Vaccinated dogs that develop antibodies before challenge have very high probability of surviving any challenge, regardless of virus dose or strain 6

The role of passive immunization is complementary to vaccination, providing immediate short-term protection while active immunity develops, rather than serving as a standalone preventive measure 3