Can I get the flu shot when I'm sick?

Flu Vaccination During Illness

You should not get the flu shot when you have a moderate to severe febrile illness, but minor illnesses with or without fever, such as mild upper respiratory infections or allergic rhinitis, do not contraindicate influenza vaccination. 1

Guidelines for Vaccination During Illness

• Persons with acute febrile illness usually should not be vaccinated until their symptoms have abated 1
• Minor illnesses with or without fever do not contraindicate the use of influenza vaccine, particularly among children with mild upper respiratory tract infection or allergic rhinitis 1
• For those with moderate to severe febrile illness (e.g., high fever, active infection, requiring hospitalization), vaccination should be deferred until resolution of the illness, based on clinical judgment 1
• Children with confirmed COVID-19 can receive the influenza vaccine when the acute illness has resolved and/or the illness is mild 1

Rationale for Deferring Vaccination During Significant Illness

• Deferring vaccination during moderate to severe illness helps avoid:

  • Confusing post-vaccination symptoms with those of the current illness 1
  • Potentially bringing infectious persons into vaccination settings where they might expose others 1
  • Reduced immune response to the vaccine during significant illness 1

• For persons with COVID-19, vaccination should usually be deferred until they have recovered, especially for those with moderate or severe COVID-19 1

• For those with mild or asymptomatic COVID-19, further deferral might be considered to avoid confusing COVID-19 symptoms with post-vaccination reactions 1

Special Considerations

• Children with nasal congestion that would notably impede delivery of live attenuated influenza vaccine (LAIV) into the nasopharyngeal mucosa should have LAIV deferred until resolution or may receive the inactivated influenza vaccine (IIV) instead 1
• The timing of vaccination after illness should consider:
  • The risk factors for severe influenza illness in the individual 1
  • The likelihood of being able to vaccinate at a later date 1
  • The current level of influenza activity in the community 1

Common Misconceptions and Pitfalls

• Many people incorrectly believe that any illness is a contraindication to receiving the flu vaccine 1
• Some mistakenly think the flu vaccine can cause influenza, which is impossible with inactivated vaccines 1
• Coincidental respiratory disease unrelated to vaccination can occur after vaccination and may be incorrectly attributed to the vaccine 1
• Delaying vaccination unnecessarily may result in missed opportunities for protection before influenza season peaks 1

Best Practices for Vaccination Timing

• The optimal time for influenza vaccination is generally October through November in the Northern Hemisphere 1
• Even if vaccination is delayed due to illness, it should still be administered as soon as the illness resolves, even if influenza activity has already been documented in the community 1
• Vaccination efforts should continue throughout the influenza season as long as vaccine supplies are available 1