Effectiveness of antiviral prophylaxis as a containment measure duringan influenza epidemic

Abstract

Influenza epidemics have always been a constant public health threat to human populations. Recent societal developments and demographics changes have put us at increased risk of a widespread and potentially deadly influenza epidemic. Antiviral prophylaxis may provide an important epidemic intervention measure especially against influenza epidemic caused by novel influenza viruses where there will be no effective epidemic-specific vaccines available at the initial phase of the epidemic. Antiviral prophylaxis is listed as a fundamental component of the Hong Kong Preparedness Plan for Influenza Pandemics, however the rationale of such plan is not supported by public presentation of scientific evidence and no details of the actual antiviral prophylaxis plan are provided. With a majority of its stockpile set to expire in the very near future, we would like to know if antiviral prophylaxis is an effective intervention strategy against influenza epidemic and should antiviral stockpiling be continued.

We identified relevant studies and reviewed the effectiveness of antiviral prophylaxis in preventing influenza infections at the individual, household and population level. We found that prophylactic treatment with Oseltamivir or Zanamivir are both effective in preventing influenza infections at the individual and household level. Both antivirals are well tolerated and neither is associated with major adverse events. Antiviral prophylaxis is effective in mitigating the public health impact of an influenza epidemic such as number of clinical influenza infections, hospitalization and deaths. However, antiviral prophylaxis alone may not be sufficient to contain or avert an influenza epidemic or delay the epidemic progress long enough for public health resources such as epidemic-specific vaccines to be acquired. In addition, the emergence of antiviral resistance and various logistics constraints will hamper the effectiveness of antiviral prophylaxis in containing influenza epidemics. We suggest the use of antiviral prophylaxis as the key intervention to mitigate influenza epidemics, however, with special considerations taken into hedging antiviral resistance and fulfilling the logistics requirements in order to make antiviral prophylaxis effective. In addition, we recommend public health authorities to take a multi-factorial approach in tackling highly transmissible influenza epidemics by incorporating other non-pharmaceutical interventions such as quarantine, school closures and boarder restrictions into the their antiviral prophylaxis-based containment plan.