Vaccines & Immunizations

There are two ways to give immunity. Active immunity — what a vaccine provides — exposes the body to a harmless piece or weakened form of a pathogen so the person’s own immune system builds antibodies and memory cells. It takes weeks to develop but lasts for years. Passive immunity — from immunoglobulins/antibodies (e.g., after a rabies or tetanus exposure, or maternal antibodies to a newborn) — gives ready-made antibodies that work immediately but wear off in weeks to months because the body never learned to make its own.

Vaccines are the classic public-health intervention: prevention, not treatment.

The single most important nursing distinction is whether a vaccine is live-attenuated (a weakened but living organism) or non-live (inactivated, subunit, toxoid, or mRNA). Live vaccines — MMR, varicella, MMRV, intranasal (live) influenza, rotavirus, yellow fever, BCG — replicate mildly to provoke strong immunity, but that replication is dangerous for anyone who can’t control it.

Therefore live vaccines are contraindicated in significant immunocompromise (chemotherapy, high-dose steroids, HIV with low CD4, transplant) and in pregnancy — the weakened organism could cause disease. Non-live vaccines can’t replicate, so they’re safe in these groups. If multiple live vaccines are needed, give them the same day or ≥ 4 weeks apart.

Real contraindications are narrow: a severe allergic reaction (anaphylaxis) to a prior dose or vaccine component, the live-vaccine restrictions above, and a few specific situations (e.g., encephalopathy after pertussis). Crucially, a minor illness (low-grade cold) is NOT a reason to defer vaccination, and neither are most mild reactions. Over-cautious deferral leaves patients unprotected.

Expected effects are local (sore, red arm) and mild systemic (low-grade fever, malaise) — signs the immune system is responding. Serious allergic reactions are rare, so patients are observed briefly and providers keep epinephrine available. Immunization schedules are set by the CDC.