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HKU researchers find that topical imiquimod before intradermal injection enhances the protection by flu vaccine in elderly patients with medical illness

28 Jul 2014

Every year many elderly patients were hospitalized for influenza infection and its complication, of which 10% has received the conventional intramuscular seasonal influenza vaccination in the past 9 months.  This breakthrough in protection is often attributed to the falling protective antibody titre within 6 months after the winter vaccination.  Elderly patients with medical comorbidities are particularly vulnerable and rendered susceptible to the summer influenza peak or just before the next annual vaccination.  A team led by Professor Yuen Kwok-yung, Chair Professor of Department of Microbiology, Li Ka Shing Faculty of Medicine of The University of Hong Kong (HKU) has discovered a simple and practical way of protecting elderly patients with medical illness from seasonal influenza.  By applying imiquimod before intradermal injection, the protection by flu vaccine will be enhanced, thus decreasing the risk of hospitalization.  The study has been published in the leading medical journal Clinical Infectious Disease.

Research Implications

One of the leading researchers, Professor Yuen Kwok-yung, Henry Fok Professor in Infectious Diseases and Chair Professor of Department of Microbiology, Li Ka Shing Faculty of Medicine of HKU said “We found that our new vaccination method can hasten, enhance and prolong the protective effect of the influenza vaccine, giving the elderly patients with comorbidities better protection against flu.”

Study method and findings

In the current study, a total of 91 Chinese subjects were enrolled into a double blind randomized controlled trial.  The median age was 73 years.  30 subjects received topical imiquimod pretreatment followed by intradermal influenza vaccination, compared to 30 subjects who received the inactive aqueous cream followed by intramuscular influenza vaccination and 31 subjects who received the inactive aqueous cream followed by intradermal influenza vaccination.  Imiquimod is a very safe immune-stimulatory drug, which was used topically to treat skin wart for many years.  

Intradermal injection after pretreatment with topical imiquimod over the injection site expedited, augmented and prolonged the immunogenicity of influenza vaccination.  The antibody production appeared two weeks earlier and was sustained for at least one year.  The vaccine recipients had only minor self-limiting adverse effects but were less often hospitalized for influenza or pneumonia.

About the research team

The research team was led by Professor Yuen Kwok-yung, Henry Fok Professor in Infectious Diseases, Chair Professor of Department of Microbiology and co-director of the State Key Laboratory of Emerging Infectious Diseases, Li Ka Shing Faculty of Medicine and Dr Ivan Hung Fan-ngai, Clinical Associate Professor of Department of Medicine, Li Ka Shing Faculty of Medicine, HKU.  The study was partly funded by the Research Fund for the control of infectious disease, the Food and Health Bureau.