Immunization Principles
Principles and the US routine childhood schedule (CDC/AAP)
Live vaccines
MMR, varicella, rotavirus (oral), live nasal influenza (LAIV), yellow fever, oral typhoid. (BCG and oral polio are not used routinely in the US.)
- Not in pregnancy or severe immunosuppression (e.g., chemotherapy, high-dose steroids).
- Two live injected vaccines: same day or ≥28 days apart.
- After blood products or IVIG: live vaccines may need to be delayed (months).
Contraindications vs. not
True contraindication: severe allergic reaction (anaphylaxis) to a previous dose or a vaccine component.
Precaution: moderate or severe acute illness (delay).
Not reasons to delay: mild illness or low fever, taking antibiotics, breastfeeding, prematurity (vaccinate by chronological age), egg allergy (any flu vaccine can be given).
Giving the injection
| Who | IM site | Needle (typical) |
|---|---|---|
| Newborns and infants | Vastus lateralis (anterolateral thigh) | ⅝–1 in, 22–25 G |
| Toddlers 1–2 yr | Vastus lateralis (preferred) or deltoid if enough muscle | ⅝–1¼ in |
| 3 years and older | Deltoid (thigh if needed) | ⅝–1 in |
- Subcutaneous vaccines (MMR, varicella): fatty tissue of the thigh (infants) or upper outer arm.
- Rotavirus is oral: first dose by 14 weeks 6 days; last dose by 8 months.
- No need to aspirate. Give the most painful vaccine last. Comfort: breastfeeding, sucrose, holding, distraction.
- Observe 15 minutes (adolescents seated: fainting risk). Keep epinephrine available.
- Document vaccine, lot, site, date and the information given.
US routine childhood schedule (AAP / CDC)
| Age | Vaccines |
|---|---|
| Birth | Hep B #1 (within 24 h) · RSV antibody (nirsevimab or clesrovimab) Oct–Mar if mother not vaccinated |
| 1–2 months | Hep B #2 |
| 2 months | DTaP, Hib, IPV, PCV, rotavirus |
| 4 months | DTaP, Hib, IPV, PCV, rotavirus |
| 6 months | DTaP, PCV, Hib and rotavirus (brand-dependent) · Hep B #3 and IPV #3 (6–18 mo) · influenza yearly from 6 months (2 doses the first season if <9 yr) |
| 12–15 months | MMR #1, varicella #1, Hib and PCV boosters · Hep A (2 doses, 6 months apart, by 23 mo) |
| 15–18 months | DTaP #4 |
| 4–6 years | DTaP #5, IPV #4, MMR #2, varicella #2 |
| 11–12 years | Tdap, HPV (can start at 9), MenACWY #1 |
| 16 years | MenACWY booster · MenB (16–23 yr, shared decision) |
Also: Tdap in every pregnancy (27–36 wk); COVID-19 vaccination per current CDC/AAP guidance.
US schedule in 2026
Federal changes to the childhood schedule (Dec 2025 ACIP votes and a Jan 2026 CDC schedule) were blocked by a federal court in March 2026, restoring the previous schedule while appeals continue. The AAP schedule above reflects standard teaching and NCLEX. Check the current CDC/AAP schedule before clinicals.