Live Vaccines: Types and Considerations
Live vaccines contain attenuated (weakened) forms of viruses or bacteria that can replicate in the body but are modified to prevent disease while still stimulating an immune response. 1
Types of Live Viral Vaccines
- MMR (Measles, Mumps, Rubella) - A commonly administered live viral vaccine that provides protection against three different viral diseases 1
- MMRV (Measles, Mumps, Rubella, Varicella) - Combination vaccine that adds protection against chickenpox 2
- Varicella (Chickenpox) vaccine - Prevents primary varicella infection 1, 3
- Zoster vaccine live (ZVL) - For prevention of herpes zoster (shingles) in older adults 1
- Rotavirus vaccine - Oral vaccine for prevention of severe diarrheal disease in infants 1
- Yellow fever vaccine - For prevention of yellow fever in travelers to endemic areas 1
- LAIV (Live Attenuated Influenza Vaccine) - Nasal spray influenza vaccine 1
- Oral polio vaccine (OPV) - No longer available in the United States 1
Types of Live Bacterial Vaccines
- BCG (Bacille Calmette-Guérin) - For tuberculosis prevention 1
- Ty21a Salmonella Typhi - Oral typhoid vaccine 1
Administration Considerations
- Live vaccines stimulate both humoral (antibody) and cellular immune responses by causing a mild, non-pathogenic infection 4
- When administering multiple live vaccines, they should either be given on the same day or separated by at least 4 weeks 5
- If two live parenteral vaccines are administered less than 4 weeks apart, the second vaccine dose should be repeated after waiting at least 4 weeks from the invalid dose 5
- Simultaneous administration of indicated vaccines increases the likelihood of complete vaccination and provides timely protection 5
Contraindications
- Pregnancy - Live vaccines are generally contraindicated during pregnancy due to theoretical risk to the fetus 1
- Immunocompromised patients - Live vaccines are typically contraindicated in patients with:
- Severe combined immunodeficiency (SCID) 1
- Complete DiGeorge syndrome 1
- HIV/AIDS with severe immunosuppression 1
- Active malignancy on immunosuppressive therapy 1, 6
- Solid organ transplantation on immunosuppressive medications 6
- Recent bone marrow transplantation (within 2 years) 6
- High-dose corticosteroids or other immunosuppressive medications 1, 6
Special Considerations for Immunocompromised Patients
- Patients with B-cell (humoral) deficiencies may have uncertain responses to vaccines that depend primarily on antibody response 1
- Patients with T-cell deficiencies should generally avoid all live vaccines 1
- Patients with complement deficiencies can typically receive all routine vaccines including live vaccines 1
- Patients with phagocytic function defects (e.g., chronic granulomatous disease) should avoid live bacterial vaccines but can usually receive live viral vaccines 1
Safety and Efficacy
- Most studies show that live vaccines are safe and sufficiently immunogenic in immunocompetent individuals 6
- Serious adverse events from live vaccines are rare but can include vaccine-strain infections, which are typically mild 6
- Fatal infections have been reported in severely immunocompromised patients who received live vaccines 6
- The immunogenicity of live vaccines may be reduced in patients on certain immunosuppressive therapies such as methotrexate or TNF inhibitors 6
Future Directions
- Combined live vaccine vectors are being developed where genes encoding vaccine antigens are inserted into non-pathogenic viruses or bacteria 4, 7
- These multivalent vaccines may induce immunity to multiple diseases with a single dose 7
Live vaccines remain a crucial component of immunization programs worldwide, providing effective protection against numerous infectious diseases when appropriately administered to suitable candidates.