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Imiquimod improved immunogenicity of flu vaccine in older adults
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In older adults with comorbidities, pretreatment with topical imiquimod appears to significantly hasten, improve and extend the immunogenicity of influenza vaccination, according to recent findings.
In a double blind, randomized controlled trial, researchers recruited 91 adults aged at least 21 years who were seen at medical specialist outpatient clinics in Hong Kong. Most of these patients had comorbidities and were aged at least 65 years.
Patients were randomly assigned to one of three vaccination regimens: an experimental group receiving topical 5% 250 mg imiquimod ointment followed by intradermal trivalent influenza vaccine (Intanza, Sanofi Pasteur; n=30), and two control groups administered either topical aqueous cream followed by intradermal TIV (n=31) or topical aqueous cream followed by intramuscular TIV (Vaxigrip, Sanofi Pasteur; n=30). Patients were followed up to 1 year post-vaccination, and all hospitalizations for influenza or pneumonia were chronicled.
The study’s primary outcome was the seroconversion rate at 7 days.
The researchers found that at the 7-day follow up, 90% of patients who underwent treatment with imiquimod and intradermal TIV achieved seroconversion against the H1N1 strain by hemagglutination inhibition vs. 13.3% of those who received aqueous cream and intramuscular TIV (P<.001) and 38.7% of those who received aqueous cream and intradermal TIV (P<.001). Increases in seroconversion, seroprotection and geometric mean titer fold were met 2 weeks earlier in all three strains in the imiquimod and intradermal TIV groups. The superior seroconversion rate was maintained from day 7 to year 1 (P≤.001). Patients with lower rates of hospitalization for influenza or pneumonia were found to have better immunogenicity (P<.05). Adverse effects were self-limited.
“Application of imiquimod prior to intradermal vaccination has expedited and augmented the immunogenicity of influenza vaccination in elderly subjects,” the study researchers wrote. “By day 7 of vaccination, seroconversion, geometric mean titer, and geometric mean titer fold increase against all three influenza strains was significantly higher in the imiquimod group than both controls. This strategy of influenza immunization should be considered in the elderly population.”
Disclosure: The researchers report no relevant financial disclosures.
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