Live vaccines: who should not receive them !
- Topic
Live vaccines carry a weakened germ. With very weak defences or in pregnancy they can be dangerous, so they have clear contraindications.
Updated 2026-11-01
See it in 3D: Thymus
What it is
A contraindication is a condition that raises the risk of a serious reaction, and the vaccine is not given; a precaution means weighing benefit against risk. Live attenuated vaccines can replicate unchecked when the immune system is badly compromised, and they carry a theoretical risk to the fetus. Knowing who must not receive them, and who can even when it seems otherwise, is a frequent exam question.
Key facts
- General contraindication: prior anaphylaxis to the vaccine or one of its components (applies to all vaccines).
- Severe immunodeficiency: combined primary immunodeficiencies, leukemia, lymphoma, generalized cancer, recent chemotherapy or radiotherapy and prolonged high-dose corticosteroids.
- After chemotherapy or radiotherapy stops, wait at least 3 months before a live vaccine.
- Pregnancy: MMR and varicella are not given; avoiding pregnancy for one month after receiving them is advised.
- Rotavirus: contraindicated in severe combined immunodeficiency (SCID) and after a history of intussusception.
- Yellow fever: not given under 6 months of age or with thymus disease; in pregnancy only when exposure cannot be avoided.
- HIV: MMR and varicella can be given to children without severe immunosuppression (CD4 at least 15 %).
Common situations and live vaccines
| Situation | Live vaccine? | Comment |
|---|---|---|
| Severe combined immunodeficiency (SCID) | No | Risk of disseminated infection by the vaccine strain; includes rotavirus and BCG |
| Pregnancy | No | Theoretical fetal risk; inactivated influenza and pertussis vaccines are given |
| Prolonged high-dose corticosteroids | No, while they last | Wait until immunity recovers |
| HIV without severe immunosuppression | MMR and varicella yes | Decided by CD4; BCG is not given to infants with HIV |
| Immunosuppressed or pregnant household member | Yes | The vaccinated contact shields the vulnerable person |
| Egg allergy | MMR yes | Yellow fever does require assessing severe egg allergy |
Clinical notes
- Not contraindications: living with an immunosuppressed or pregnant person, mild illness with or without fever, antibiotic use, penicillin allergy, or egg allergy for MMR.
- Recent antibody-containing blood products or immune globulin can cancel MMR and varicella; an interval set by the product is kept.
- Two injected live vaccines are given on the same day or at least 4 weeks apart.
- Moderate or severe acute illness is a precaution: the vaccine is postponed, not cancelled.
Test yourself
Think of the answer, then tap the question to see it.
What two specific contraindications does the rotavirus vaccine have?
Severe combined immunodeficiency (SCID) and a history of intussusception.
Can MMR be given to the child of a mother on chemotherapy?
Yes. Living with an immunosuppressed person does not contraindicate live vaccines; vaccinating the child protects the mother.
Why can a recent transfusion make the measles vaccine fail?
Transferred antibodies neutralize the vaccine virus before it replicates, so no active immunity develops.
Which history contraindicates the yellow fever vaccine at any age?
Thymus disease (for example thymoma, or thymectomy for that reason), as well as prior anaphylaxis to its components.
See it in 3D
The structures of Durgical's 3D anatomy where it is found.
Related
- Vaccine types: live, inactivated, subunit, toxoid, mRNA, vector
- Passive immunization: immunoglobulins and antitoxins
- Colombia's PAI schedule (which vaccines, at what age)
- Flow cytometry and the CD4 count
- T-cell and combined deficiencies: DiGeorge, SCID, Wiskott–Aldrich, ataxia-telangiectasia
- Secondary immunodeficiency: HIV, malnutrition, drugs, asplenia
- Thymus: where T cells learn
Related conditions
Microorganisms
Educational content on the immune system; not a treatment or individual vaccination guide and no substitute for a health professional's advice. No doses are given.
Sources: Contraindications and Precautions (Centers for Disease Control and Prevention (CDC), 2024); Chapter 2: General Best Practice Guidance for Immunization | Pink Book | CDC (Centers for Disease Control and Prevention (CDC), 2021); ¿Cómo funcionan las vacunas? (Ministerio de Salud y Protección Social de Colombia, 2026).
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Representative model, for educational purposes only.