Is it safe to receive the influenza (flu) vaccine during an active influenza infection?

Influenza Vaccination During Active Influenza Infection

It is preferable to delay influenza vaccination in adults with acute febrile illness until their symptoms have abated, though minor illnesses with or without fever do not contraindicate the use of influenza vaccine. 1, 2

Safety of Vaccination During Influenza Infection

• The Advisory Committee on Immunization Practices (ACIP) recommends delaying vaccination for adults with acute febrile illnesses until symptoms have resolved 1
• This recommendation is primarily to avoid confusing symptoms of the illness with possible adverse effects from the vaccine 2
• Minor illnesses with or without fever should not contraindicate influenza vaccination, particularly among children with mild upper respiratory tract infection or allergic rhinitis 1
• The primary concern is distinguishing between vaccine side effects and ongoing illness symptoms, not safety issues 2

Considerations by Illness Severity

Mild Symptoms or Resolving Illness

• Recent viral infections without fever or with resolving symptoms are not a contraindication to receiving the flu vaccine 2, 3
• Unnecessarily postponing vaccination in patients with minor illnesses can lead to missed opportunities for protection 2

Acute Febrile Illness

• Moderate-to-severe febrile illness warrants postponing vaccination until resolution, based on clinical judgment 3
• This is a precaution, not an absolute contraindication 2

Vaccine Type Considerations

Injectable Influenza Vaccines

• Injectable influenza vaccines can be safely administered during rhinitis regardless of severity 3
• No special precautions are needed beyond standard vaccination practices 3

Live Attenuated Influenza Vaccine (LAIV - nasal spray)

• LAIV can be administered with mild rhinitis 3
• Should be deferred if nasal congestion would notably impede vaccine delivery into the nasopharyngeal mucosa 3

Important Clinical Considerations

• Influenza vaccine contains only noninfectious viruses and cannot cause influenza 1
• Respiratory disease after vaccination represents coincidental illness unrelated to influenza vaccination 1
• The most common side effects of vaccination are soreness at the vaccination site (less than one-third of vaccinees), fever, malaise, and myalgia 1
• These side effects typically begin 6-12 hours after vaccination and can persist for 1-2 days 1

Common Pitfalls to Avoid

• Mistaking the need to delay vaccination during acute febrile illness as a need to delay during any viral infection, including mild ones 2
• Failing to recognize that nasal congestion is only a consideration for the nasal spray vaccine (LAIV), not for injectable vaccines 2, 3
• Not distinguishing between contraindications and precautions, which can lead to unnecessary delays in vaccination 2
• Missing opportunities for vaccination by unnecessarily postponing it in patients with minor illnesses 2

Conclusion

While it is generally preferable to delay influenza vaccination during acute febrile illness until symptoms resolve, this is primarily to avoid confusion between illness symptoms and vaccine side effects rather than due to safety concerns. Minor illnesses with or without fever do not contraindicate influenza vaccination, and unnecessarily postponing vaccination can lead to missed opportunities for protection against influenza.