Could the flu vaccine be causing my right‑sided penile pain that occurs just before and briefly after ejaculation, which started the day after vaccination?

Flu Vaccine and Penile Pain: No Established Connection

The flu vaccine is extremely unlikely to be causing your right-sided penile pain associated with ejaculation, as this symptom is not a recognized adverse effect of influenza vaccination in any published guidelines or surveillance data.

Known Adverse Effects of Influenza Vaccination

The documented side effects of influenza vaccines are well-established and do not include genitourinary symptoms:

• Local reactions (soreness, redness, swelling at injection site) occur in 10-64% of recipients and last less than 2 days 1
• Systemic reactions (fever, malaise, myalgia) begin 6-12 hours post-vaccination and persist 1-2 days, primarily in those without prior antigen exposure 1
• Rare serious reactions include Guillain-Barré syndrome (approximately 1-2 cases per million vaccinees) and severe allergic reactions in egg-allergic individuals 1
• Gastrointestinal symptoms (nausea) are less common 1

Notably, the CDC's Advisory Committee on Immunization Practices (ACIP) and extensive VAERS surveillance have never identified genitourinary symptoms, including penile pain or ejaculatory pain, as adverse effects of influenza vaccination 1, 2, 3.

Actual Causes of Painful Ejaculation

Your symptom—right-sided penile pain occurring just before and briefly after ejaculation—has a prevalence of 1-25% in the general male population and is associated with specific urological conditions 4, 5:

Primary Etiologies to Investigate:

• Prostatitis/chronic pelvic pain syndrome: The most common cause, with painful ejaculation reported in 18.6% of men with lower urinary tract symptoms 6, 7
• Benign prostatic hyperplasia (BPH): Men with BPH and painful ejaculation have more severe symptoms and greater bother 6
• Ejaculatory duct obstruction: Can cause unilateral or bilateral ejaculatory pain 4, 5
• Urinary tract infection: Reported in 12% of men with ejaculatory pain versus 7% without 6
• Seminal vesicle pathology: Including stones or inflammation 5
• Medication side effects: Particularly antidepressants 4, 5

Clinical Reasoning for Temporal Coincidence

The timing (symptom onset the day after vaccination) represents temporal association, not causation:

• Respiratory or genitourinary symptoms occurring after vaccination typically represent coincidental illnesses unrelated to the vaccine 8, 2
• The influenza vaccine contains only noninfectious killed viruses and cannot cause systemic infections or inflammation in distant organ systems 1, 8
• Given the 1-25% background prevalence of painful ejaculation in men, coincidental onset is statistically expected 4

Recommended Diagnostic Approach

Pursue standard urological evaluation immediately rather than attributing symptoms to vaccination:

• Urinalysis and urine culture to exclude urinary tract infection 6
• Digital rectal examination to assess for prostate tenderness, nodules, or enlargement 6, 7
• Expressed prostatic secretions or post-massage urine if prostatitis is suspected 7
• Prostate-specific antigen (PSA) if clinically indicated 6
• Transrectal ultrasound if ejaculatory duct obstruction or seminal vesicle pathology is suspected 4, 5
• Medication review for drugs associated with ejaculatory dysfunction 4, 5

Common Pitfall to Avoid:

Do not delay appropriate urological investigation by incorrectly attributing symptoms to vaccination—this can lead to progression of treatable conditions like prostatitis or urinary tract infections 4, 7.

Treatment Considerations

Management depends entirely on the underlying etiology identified through proper evaluation:

• Bacterial prostatitis: Appropriate antibiotic therapy 7
• Chronic prostatitis/chronic pelvic pain syndrome: Alpha-blockers, anti-inflammatories, pelvic floor physical therapy 4
• Ejaculatory duct obstruction: May require surgical intervention 4, 5
• Medication-induced: Consider alternative agents 4

The benefits of influenza vaccination in preventing influenza and its severe complications far outweigh the potential risks of rare adverse effects, and your symptom should not be attributed to the vaccine without thorough urological evaluation 2, 3.