Examqo › Examqo library › Pediatrics › Paediatric infectious disease · IMLE
Principles of childhood vaccination
Most vaccine questions are not about the schedule but about a decision — may we vaccinate now? — and three principles answer it: live versus inactivated, true versus false contraindications, and the intervals between vaccines and blood products.
Why it matters in the exam
Exam cases describe a child with a mild fever, egg allergy, an immunosuppressed sibling, recent steroids or IVIG, and ask whether to vaccinate. The correct answer almost always rests on whether the vaccine is live, and on knowing that most "reasons to delay" are false contraindications. The Israeli schedule is set by the Ministry of Health (Tipat Halav) and is updated, so the current table should be checked before memorising ages.
Other recurring points: the rotavirus vaccine — first dose only up to 15 weeks of age, contraindicated after a previous intussusception; a baby of an HBsAg-positive mother receives the vaccine and HBIG within 12 hours of birth; a preterm baby is vaccinated by chronological age; and a pregnant woman receives Tdap in every pregnancy to protect the baby from pertussis. Live vaccines are not given in pregnancy.
Key points
- Live vaccines are contraindicated in pregnancy and significant immunosuppression.
- True contraindication: anaphylaxis to a component or a previous dose.
- Mild illness, antibiotics and egg allergy are not reasons to delay.
- Two injected live vaccines: on the same day or at least 28 days apart.
- Baby of an HBsAg-positive mother: vaccine and HBIG within 12 hours.
Summary table
| Question | The rule | Examples |
|---|---|---|
| Live or inactivated? | Live: MMR, varicella, rotavirus, BCG, OPV, nasal influenza | Live vaccines are contraindicated in pregnancy and significant immunosuppression |
| True contraindications | Anaphylaxis to a previous dose or a component; encephalopathy within 7 days of a pertussis vaccine | After encephalopathy — no further pertussis component |
| Not contraindications | Mild illness with low fever, antibiotics, prematurity, breastfeeding, family history of seizures, local reaction | Egg allergy does not prevent MMR or influenza vaccine |
| Steroids | Prednisone 2 mg/kg per day (or 20 mg per day) for at least 14 days = immunosuppression | Live vaccine only one month after stopping |
| Intervals | Two injected live vaccines: on the same day or at least 28 days apart | After IVIG or blood products — delay MMR and varicella (up to 11 months after high-dose IVIG) |
In the full version for subscribers
- A simple algorithm
- Memory aid
- Exam traps
- 5 review cards
- Enough for IMLE
The full version is open to subscribers of: Pediatrics, Medical licensing exam (IMLE), Family medicine, Public health.
Subscriber? Read the full topic Plans and prices 25 free questions
Sources
- Israel Ministry of Health — Routine childhood vaccination schedule (Tipat Halav), current edition — Vaccination schedule and guidance for professionals
- CDC/ACIP General Best Practice Guidelines for Immunization, current edition — Contraindications and precautions; timing and spacing
- Nelson Textbook of Pediatrics, 22nd edition (2024) — Immunization Practices
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-02. The text may contain errors; when in doubt, check the source.