Can a flu shot be administered to someone who is currently sick?

Can You Give a Flu Shot When Sick?

Yes, you can administer the flu vaccine to someone with minor illness (including mild upper respiratory infections, low-grade fever, or diarrhea), but you should defer vaccination if the person has moderate to severe acute febrile illness until symptoms resolve. 1

Clinical Decision Framework

Minor Illness - Proceed with Vaccination

The following conditions do not contraindicate influenza vaccination and you should proceed 1, 2:

• Mild upper respiratory infections (runny nose, mild sore throat) with or without fever 3, 1
• Allergic rhinitis 3, 1
• Low-grade fever without moderate-to-severe systemic symptoms 1
• Mild diarrhea 1
• Minor acute illnesses with or without fever 3

For injectable inactivated vaccines, even moderate rhinitis poses no concern since the vaccine is delivered intramuscularly and minor respiratory symptoms do not affect vaccine delivery or efficacy 1.

Moderate to Severe Illness - Defer Vaccination

You should defer vaccination until recovery when 3, 1, 2:

• Moderate to severe acute febrile illness is present 3, 1
• The patient appears systemically ill with significant fever, malaise, or other constitutional symptoms 1
• Clinical judgment indicates the person is acutely unwell beyond minor symptoms 3

This deferral is a precaution, not an absolute contraindication - the primary concern is avoiding confusion between vaccine side effects and the progression of the underlying illness 1.

Special Considerations by Vaccine Type

Inactivated Injectable Vaccines (IIV)

• Can be safely administered during any severity of rhinitis with no special precautions 1
• Minor respiratory symptoms do not affect vaccine delivery or efficacy 1

Live Attenuated Intranasal Vaccine (LAIV)

• Can be given with mild rhinitis 3, 1
• Should be deferred if significant nasal congestion would impede vaccine delivery to the nasopharyngeal mucosa 3, 1
• If the patient sneezes after administration, do not repeat the dose 3

COVID-19 Context

For patients with confirmed COVID-19 3:

• Defer vaccination if moderate or severe illness until recovery 3
• For mild or asymptomatic COVID-19, consider further deferral to avoid confusing COVID-19 symptoms with post-vaccination reactions 3
• Do not bring patients in quarantine or isolation to vaccination settings if doing so could expose others 3

Key Safety Points

The vaccine cannot cause influenza or worsen current infections 3, 2. The influenza vaccine contains only noninfectious viruses - any respiratory illness occurring after vaccination represents either coincidental illness or pre-existing infection that was incubating at the time of vaccination 2.

Common post-vaccination symptoms include 2:

• Local reactions (soreness, redness at injection site) in 10-64% of recipients 2
• Systemic symptoms (fever, malaise, myalgia) beginning 6-12 hours post-vaccination, lasting 1-2 days 3, 2

These are self-limited and distinct from influenza infection 2.

Common Pitfalls to Avoid

• Do not over-defer vaccination for minor symptoms like mild cold, low-grade fever, or allergic rhinitis 1
• Do not confuse precautions with contraindications - moderate-to-severe illness is a precaution requiring clinical judgment, not an absolute contraindication 1
• Do not delay vaccination unnecessarily - there is no required waiting period after recovery from influenza infection before administering the vaccine, only that the person has clinically recovered from acute illness 2
• Do not withhold vaccination from children with mild upper respiratory infections, as minor illnesses should not contraindicate vaccine use in this population 3, 1