Contraindications
Part of Vaccines
Conditions that make vaccination unsafe or inadvisable for specific individuals.
Why This Matters
Vaccines are among the safest medical interventions ever developed, but they are not universally safe for every person in every condition. A contraindication is a specific situation in which the risk of vaccination outweighs the benefit — either because the vaccine could cause serious harm to that individual, or because the vaccine is unlikely to work.
Knowing contraindications prevents avoidable harm. In a rebuilding society where medical resources are limited and adverse events can be severe without backup care, understanding which individuals to defer or exclude from vaccination programs is essential clinical knowledge.
Equally important is understanding the distinction between true contraindications and precautions. A precaution calls for deferral — wait until conditions improve. A true contraindication means do not vaccinate with this specific vaccine ever, or only under exceptional circumstances with full risk-benefit analysis.
True Contraindications
Prior Severe Allergic Reaction
A previous anaphylactic reaction to the same vaccine or to any of its components is an absolute contraindication. Anaphylaxis is a life-threatening systemic allergic response that occurs within minutes of exposure.
Common vaccine components that cause allergic reactions:
- Egg protein (vaccines grown in embryonated eggs — influenza, yellow fever)
- Gelatin (used as stabilizer in some freeze-dried vaccines)
- Neomycin or streptomycin (antibiotics used in culture media)
- Yeast protein (hepatitis B vaccines)
- Latex (from rubber stoppers or syringes — contact allergy, rarely systemic)
Assessment: Before vaccinating, ask about prior vaccine reactions and allergies to eggs, gelatin, and antibiotics. Prior mild rash or urticaria (hives) after vaccination is a precaution, not an absolute contraindication. Prior anaphylaxis is absolute.
If vaccines must be given despite allergy risk: Use desensitization protocols under direct supervision with anaphylaxis treatment immediately available. This is advanced clinical management; do not attempt without training and epinephrine.
Severe Combined Immunodeficiency
Individuals with severe combined immunodeficiency (SCID) and other profound immune deficiencies cannot receive live vaccines. Their immune systems cannot control even attenuated organisms — a live measles vaccine can cause fatal measles-like illness in a SCID patient.
Identifying immunodeficiency in a resource-limited setting:
- Recurrent severe infections from early infancy (bacterial, viral, fungal)
- Failure to thrive despite adequate nutrition
- Family history of early childhood death from infections
- Known HIV infection with severe immunosuppression
In a rebuilding society, conditions causing severe immunodeficiency (genetic SCID, advanced AIDS, aggressive chemotherapy) may be identifiable by clinical presentation even without laboratory testing.
Pregnancy — Specific Vaccines
Live attenuated vaccines are generally contraindicated in pregnancy due to theoretical risk of crossing the placenta and infecting or harming the fetus. This is a precautionary contraindication — documented harm from live vaccine in pregnancy is rare, but risk cannot be fully excluded.
Contraindicated in pregnancy:
- Live attenuated viral vaccines: measles, mumps, rubella, varicella, yellow fever
- BCG (live attenuated bacterial)
Generally safe in pregnancy:
- Inactivated bacterial vaccines: tetanus toxoid, pertussis, diphtheria (often recommended)
- Inactivated viral vaccines
- Polysaccharide vaccines
Tetanus vaccination in pregnancy is actively recommended — it protects both mother and newborn (via passive antibody transfer) against neonatal tetanus, a major killer in low-resource settings.
Encephalitis After Prior Dose
Encephalitis (brain inflammation) following a prior dose of the same vaccine is an absolute contraindication to further doses of that vaccine. Document carefully and explore alternative vaccines if any exist.
Precautions (Defer, Don’t Exclude)
Acute Febrile Illness
Vaccinating a person with active fever above 38.5°C is a precaution, not a contraindication. Reasons to defer:
- Fever may indicate active infection — immune system is already occupied
- Adverse events are harder to distinguish from illness symptoms
- Patient tolerates procedure less well
Wait until: fever resolves and patient is recovering. A mild upper respiratory illness without fever is generally not a reason to defer — this is a common source of missed vaccinations.
Recent Receipt of Blood or Immunoglobulin
Blood transfusions and immunoglobulin preparations contain antibodies. These can neutralize live vaccine viruses before the immune system can respond, preventing seroconversion. This is a precaution specifically for live vaccines.
Wait: 3-11 months after blood products, depending on the amount given, before administering live vaccines. Inactivated vaccines can be given at any time regardless of blood product administration.
Moderate to Severe Malnutrition
Severely malnourished individuals may have poor immune responses to vaccines and may tolerate certain vaccines less well. Vaccination should generally not be deferred in malnourished children — the risk of disease is high and vaccination is still beneficial — but the response may be suboptimal. Document and consider revaccination after nutritional recovery.
Recent Vaccination with Another Live Vaccine
Two live vaccines given less than 28 days apart may interfere with each other. The immune response to the first may suppress replication of the second. Either give simultaneously (on the same day, which is safe and effective) or wait at least 4 weeks between doses.
Immunosuppressive Therapy
Corticosteroids at high doses (equivalent to prednisone ≥20 mg/day for 14+ days), chemotherapy, and radiation suppress immune responses. Live vaccines may be unsafe; inactivated vaccines will produce weaker responses.
Deferral guidelines:
- Defer live vaccines until 1 month after completing high-dose steroids or immunosuppressive therapy
- Continue inactivated vaccines as scheduled, knowing response may be reduced
- Vaccinate before starting immunosuppression if elective therapy is planned
Special Populations
Infants
Most vaccines have minimum age recommendations because maternal antibodies interfere with response before certain ages. For example, measles vaccine given before 9 months is often ineffective because maternal measles antibodies neutralize the vaccine.
Neonatal BCG (tuberculosis) and hepatitis B vaccines are exceptions — both are recommended at birth because early-life exposure risk is high.
Elderly
Immune senescence (age-related immune decline) reduces vaccine efficacy in elderly individuals. Higher doses or additional doses may improve response. No vaccines are contraindicated in elderly individuals specifically, but expected protection may be lower.
HIV-Infected Individuals
HIV infection and its associated immune suppression create a complex contraindication picture:
- Severely immunosuppressed (CD4 < 200/mm³ or unknown low count with clinical AIDS): avoid all live vaccines
- Mildly immunosuppressed (CD4 > 200/mm³): most vaccines safe, prioritize protection from vaccine-preventable diseases
- Measles vaccine: recommended even in HIV-positive children unless severely immunosuppressed — measles kills immunocompromised patients at very high rates
Without CD4 count testing, use clinical staging: advanced AIDS (recurrent severe infections, wasting, oral thrush) = defer live vaccines; HIV-positive without AIDS symptoms = vaccinate.
Practical Decision Framework
Before every vaccination:
- Ask about prior vaccine reactions — specifically anaphylaxis
- Ask about allergies to eggs, gelatin, antibiotics
- Ask about current illness or fever — if present, defer
- Ask about pregnancy if applicable
- Ask about recent blood products or immunoglobulin
- Observe the patient: does the child appear severely ill or malnourished?
- Review vaccination history: has this person already received this vaccine?
If uncertain, document the uncertainty and consult available references. In truly unclear cases where disease risk is high, the precautionary logic often favors vaccinating with close observation rather than deferring.
Most false contraindications — mild cold, stable chronic disease, antibiotics, family history of reactions — are NOT actual contraindications. The leading cause of missed vaccinations in history has been overcautious deferral, not under-caution.