What to do if I get sick after receiving COVID-19, influenza (flu), and pneumococcal (pneumonia) vaccinations?

Management of Illness Following COVID-19, Influenza, and Pneumococcal Vaccination

Most symptoms after receiving COVID-19, flu, and pneumonia vaccines are expected post-vaccination reactions that resolve within 2-3 days and require only supportive care. 1

Understanding Post-Vaccination Symptoms

Expected Timeline and Symptoms

• Systemic symptoms are common, occurring in 52-59% after the first COVID-19 vaccine dose and 39-79% after the second dose, typically beginning 6-12 hours post-vaccination 1
• Common symptoms include fatigue, headache, muscle pain, fever, and respiratory symptoms including cough 1
• Duration: Most side effects resolve within 2-3 days without specific treatment 1, 2

Immediate Management Approach

For mild symptoms (fatigue, headache, myalgia, low-grade fever, cough):

• Provide supportive care only 1
• Symptoms resolving within 2-3 days require no further evaluation 1
• Over-the-counter analgesics for symptomatic relief 2

Critical Red Flags Requiring Immediate Medical Attention

Seek urgent evaluation if you develop any of the following:

• Severe or unusual headaches 2
• New unexplained pinprick bruising or bleeding 2
• Shortness of breath or chest pain 1
• Leg swelling (particularly if starting 5+ days post-vaccination) 3, 2
• Persistent abdominal pain 1, 2

These symptoms could indicate vaccine-induced immune thrombocytopenia and thrombosis (VITT), a rare but serious complication that typically presents 5-30 days after vaccination 3, 2.

Algorithmic Approach Based on Timing

Symptoms Resolving Within Hours (0-24 hours)

• Likely vasovagal reaction (63% occur within 5 minutes, 89% within 15 minutes) 3
• Reassurance is appropriate; no further workup needed 3

Symptoms Persisting 1-3 Days

• Expected post-vaccination inflammatory response 1
• Continue supportive care
• No diagnostic testing required 1

Symptoms Persisting Beyond 3 Days

• Rule out actual infection (COVID-19, influenza, or bacterial infection) rather than vaccine reaction 1
• Perform appropriate diagnostic testing (PCR for COVID-19/influenza, cultures if bacterial infection suspected) 4
• Consider that you may have contracted an infection coincidentally around the time of vaccination 4

Symptoms Beginning 5-30 Days Post-Vaccination

• High suspicion for VITT if accompanied by leg swelling, severe headache, or bleeding 3, 2
• Immediate laboratory evaluation: complete blood count, D-dimer, anti-PF4 antibodies 3

Special Considerations

Pre-existing Respiratory Conditions

• Individuals with chronic respiratory disease may experience temporary symptom exacerbation following vaccination 1
• This typically resolves within the same 2-3 day timeframe 1

Rash Development

• Erythematous or urticarial rashes may appear approximately 10 days post-vaccination 2
• Usually resolve spontaneously within 2-4 days 2
• Treat with oral antihistamines for symptomatic relief 2
• Seek immediate care for angioedema or severe allergic reactions requiring epinephrine and systemic corticosteroids 2

Common Pitfalls to Avoid

• Do not confuse immediate benign reactions with delayed serious complications like VITT, which has a critical diagnostic window of 5-30 days 3
• Do not order extensive thrombosis workup for symptoms resolving within hours, as this represents unnecessary testing 3
• Do not dismiss persistent symptoms beyond 3 days without ruling out actual infection, as vaccination does not prevent all infections 1
• Do not assume all post-vaccination symptoms are benign if they include the red flag symptoms listed above, particularly if onset is 5+ days post-vaccination 3, 2