Immunizations and Vaccine-Preventable Disease
Core concepts
Vaccines are active (live attenuated or inactivated) or passive (immunoglobulin). Live vaccines - MMR, varicella, rotavirus, live attenuated influenza, yellow fever, oral typhoid - are contraindicated in severe immunocompromise and pregnancy. Inactivated vaccines are safe in immunocompromise but may produce weaker responses. Preterm infants are vaccinated by chronological age, with birth-weight considerations for hepatitis B. Egg allergy is not a contraindication to influenza vaccine. Recent blood products delay MMR and varicella because passive antibody neutralizes live virus. Anaphylaxis to a vaccine component is an absolute contraindication to that vaccine.
Traps
- Mild acute illness, antibiotic use, and breastfeeding are not contraindications.
- Do not give MMR or varicella to a child with severe T-cell immunodeficiency or SCID.
- Live influenza vaccine is not for immunocompromised or asthmatic children.
- Vaccine-induced immunity may wane; check titers in high-risk hosts rather than assuming protection.
Worked example
A 12-month-old with HIV and CD4 count below 15%: withhold MMR and varicella, give inactivated vaccines on schedule, and reassess immune status after antiretroviral therapy. A household contact should receive MMR to protect the child (cocooning).
Rule of thumb: in immunocompromise, inactivated vaccines are generally safe but less effective; live vaccines require an immune-status check before administration.