Vaccines

A child who is immunocompromised receives a live vaccine and develops the disease it was meant to prevent. Knowing which vaccines are live — and who cannot receive them — prevents this catastrophe.

Vaccines fall into two broad categories that drive every contraindication decision: live attenuated and inactivated (killed or subunit). Live attenuated vaccines contain weakened but replicating organisms — MMR, varicella, rotavirus, intranasal influenza (LAIV), and oral polio. Because the organism replicates, live vaccines are contraindicated in immunocompromised patients (children on high-dose corticosteroids ≥2 mg/kg/day or ≥20 mg/day of prednisone for ≥14 days, chemotherapy, HIV with severe immunosuppression, or congenital immunodeficiency). Live vaccines are also contraindicated in pregnancy. Inactivated vaccines — DTaP, IPV, Hep B, Hep A, PCV13, inactivated influenza — cannot replicate and are safe for immunocompromised children. True contraindications across all vaccines include anaphylaxis to a vaccine component or a prior dose. A moderate-to-severe acute illness with fever is a precaution warranting deferral, but mild illness with low-grade fever is NOT a reason to withhold vaccination. Egg allergy considerations apply to influenza and yellow fever vaccines; current ACIP guidelines state that egg allergy of any severity is no longer a contraindication or precaution for standard influenza vaccines. Gelatin allergy is relevant for MMR and varicella. A history of intussusception contraindicates rotavirus vaccine.

Key Distinctions

Don't confuse a true contraindication (anaphylaxis to a prior dose) with a precaution (moderate febrile illness) — precautions allow vaccination once the acute issue resolves. Students often classify all injectable vaccines as inactivated; intranasal influenza is live while the injectable form is inactivated — the route signals the type. Mild illness, current antibiotic use, and family history of adverse reactions are NOT valid reasons to defer vaccines.

Clinical Pearl

"Live vaccines Live in you" — they replicate, so never give them to a child whose immune system can't fight back. If it replicates, it's restricted.

Vaccine Administration & Parent Education

This atom focuses on the hands-on nursing role: how you give vaccines, where you give them, and what you teach families before and after. For infants under 12 months, the preferred IM site is the vastus lateralis (anterolateral thigh) using a 1-inch, 22-25 gauge needle at a 90-degree angle. After age 3, the deltoid becomes acceptable for IM injections. Subcutaneous vaccines (like MMR and varicella) use a 5/8-inch needle at a 45-degree angle in the fatty tissue of the outer thigh or upper arm. Multiple vaccines can be given at the same visit — use separate syringes, separate sites at least 1 inch apart, and document the exact site for each injection. Post-vaccination education is critical: advise parents that low-grade fever (under 101°F/38.3°C) and injection-site redness are normal immune responses, not adverse reactions. Acetaminophen may be given after vaccination for discomfort but should not be given prophylactically before, as it may blunt the immune response. Teach parents to observe for anaphylaxis signs (hives, wheezing, facial swelling) and keep the child in the clinic for at least 15 minutes post-injection — 30 minutes for a child with a history of a severe allergic reaction.

Key Distinctions

Don't confuse a normal post-vaccine response (low-grade fever, fussiness, local swelling) with a true adverse reaction (anaphylaxis, high fever above 104°F, inconsolable crying lasting 3+ hours) — the first requires reassurance, the second requires reporting to VAERS and clinical action. Students mix up IM site selection: vastus lateralis for infants, deltoid only after age 3. Never give acetaminophen before vaccination to 'prevent' fever — only after if needed.

Clinical Pearl

Thigh before three, deltoid after three. And keep every child 15 minutes post-shot — anaphylaxis doesn't wait for the parking lot.

Vaccines & Immunization Pharmacology

Vaccines work by triggering active immunity — exposing the immune system to an antigen so it builds its own antibody memory. Live attenuated vaccines (MMR, varicella, rotavirus, intranasal influenza) contain weakened organisms that replicate briefly to provoke a robust immune response. They are contraindicated in immunocompromised patients and during pregnancy. Inactivated vaccines (DTaP, IPV, hepatitis B, pneumococcal) use killed organisms or subunits and cannot cause disease but often require multiple doses to build sufficient immunity. Passive antibodies from blood products or immunoglobulins neutralize live vaccine antigens before the child's immune system can respond, so live vaccines must be delayed (typically 3–11 months depending on the product). The CDC schedule is the testable standard: hepatitis B at birth, DTaP at 2-4-6-15–18 months, MMR and varicella at 12–15 months, with boosters at 4–6 years. Mild illness with low-grade fever is NOT a contraindication to vaccination. True contraindications include anaphylaxis to a prior dose or vaccine component and severe immunodeficiency for live vaccines.

Key Distinctions

Don't confuse live attenuated (MMR, varicella — contraindicated in immunosuppression and pregnancy) with inactivated vaccines (DTaP, IPV — safe in immunocompromised patients). Students often think a mild URI with low-grade fever is a reason to delay vaccines — it is not; only moderate-to-severe acute illness warrants deferral. Recent blood product administration delays live vaccines only, not inactivated ones.

Clinical Pearl

Live means alive — no pregnancy, no immunosuppression, no recent blood products. Think: 'If the patient can't fight, don't give anything that could fight back.'