How do you treat a patient with concurrent Covid-19 and influenza (flu) infections, considering their vaccination status, underlying health conditions, and age?

Treatment of Concurrent COVID-19 and Influenza Infection

Yes, you should treat both COVID-19 and influenza simultaneously with their respective antiviral therapies when coinfection is confirmed, as coinfection occurs in approximately 0.5-2% of cases and can lead to worse outcomes if left untreated. 1

Diagnostic Approach

• Test for influenza coinfection using PCR or rapid testing of nasopharyngeal secretions when influenza is clinically suspected in any COVID-19 positive patient, as coinfection rates are documented at 0.5-2% but may be underestimated without active screening 1, 2
• Laboratory-based screening studies report higher coinfection rates than clinical diagnosis alone, suggesting many cases remain undiagnosed without routine testing 2
• Thorax radiology findings may help differentiate the predominant pathogen, though overlap exists 2

Concurrent Antiviral Treatment Protocol

For COVID-19:

• Administer remdesivir (VEKLURY) according to standard COVID-19 treatment guidelines 1, 3
• Loading dose: 200 mg IV on Day 1, followed by 100 mg IV daily (for patients ≥40 kg) 3
• Treatment duration: 5 days for non-ventilated hospitalized patients; 10 days for those requiring invasive mechanical ventilation/ECMO 3
• Initiate treatment as soon as possible after diagnosis 3

For Influenza:

• Administer oseltamivir or baloxavir according to standard influenza treatment guidelines concurrently with COVID-19 therapies without modification 1
• Do not delay influenza treatment while awaiting COVID-19 test results if clinical suspicion is high 4

Critical Drug Interaction Warning:

• If using nirmatrelvir/ritonavir (Paxlovid) for COVID-19, be aware of significant CYP3A4 interactions 4
• Consider remdesivir instead if patient is on medications with strong CYP3A4 interactions, as there are no drug-drug interactions with remdesivir 4

Bacterial Superinfection Management

Empirical antibiotics should be actively considered if bacterial superinfection cannot be ruled out, as bacterial coinfection occurs in approximately 40% of viral respiratory infections requiring hospitalization 4, 1

• Recommended empirical coverage: amoxicillin, azithromycin, or fluoroquinolones targeting community-acquired pneumonia pathogens 4
• In severe patients, empirical antibacterial treatment should cover all possible pathogens, with de-escalation once pathogenic bacteria are clarified 4
• This recommendation differs from some guidelines that discourage blind antibiotic use, but the unique severity and unpredictability of COVID-19 progression justifies this approach 4

Special Considerations by Patient Population

Immunocompromised Patients:

• Maintain bispecific antibody or immunosuppressive dosing during influenza prophylaxis if the patient is on such therapies 1
• Patients on immunosuppressive therapy have enhanced risk for severe influenza infection 4
• Consider extended antiviral treatment duration in severely immunocompromised patients 4

Pediatric Patients:

• Although hospitalization rates for COVID-19 are lower than influenza in children, in-hospital mortality is higher when coinfection occurs 5
• Adolescents (11-17 years) with COVID-19 have ten-times higher in-hospital mortality than those with influenza alone 5
• Obesity is more frequently associated with severe outcomes in adolescents with COVID-19 5

Elderly and High-Risk Adults:

• Patients with COVID-19 are more frequently obese, diabetic, hypertensive, and dyslipidemic compared to influenza patients 5
• In-hospital mortality is 2.9 times higher for COVID-19 than influenza (16.9% vs 5.8%) 5

Monitoring and Supportive Care

• Perform hepatic laboratory testing before starting remdesivir and monitor during treatment as clinically appropriate 3
• Determine prothrombin time before starting remdesivir and monitor during treatment, as prolonged APTT may be more common in certain patient groups 3, 6
• Follow standard isolation protocols for both infections until clinical resolution 1
• Monitor for acute respiratory failure, pulmonary embolism, and septic shock, which occur more frequently in COVID-19 than influenza 5

Prevention Strategies

Influenza vaccination is strongly recommended for all COVID-19 patients and their close contacts to reduce the risk of coinfection and simplify clinical management 1

• COVID-19 and influenza vaccines can be administered concurrently at different anatomical sites 7, 8
• Annual influenza vaccination is the most effective method for preventing coinfection complications 4
• Vaccination should not be delayed to separate doses—benefits of timely protection outweigh theoretical concerns 7, 8

Common Pitfalls to Avoid

• Do not wait for laboratory confirmation before initiating antiviral treatment in high-risk symptomatic patients 4
• Do not assume influenza treatment will be effective for COVID-19 or vice versa—each requires specific antiviral therapy 9
• Do not underestimate the severity of coinfection—some patients with mild symptoms can have severe radiologic features and sudden deterioration 4
• Do not delay empirical antibiotics in patients who cannot rule out bacterial superinfection, particularly given that symptoms of COVID-19 and bacterial superinfection overlap 4, 1