i LimitationsThe measures of effectiveness of AVs for reducing susceptibility and infectivity are estimated from data on strains of influenza that are currently circulating. Effectiveness with respect to a newly-emerged strain may be different. It is important to bear this in mind since the results on the use of AVs to reduce transmission are sensitive to the values of AV effectiveness parameters es, ei and et.
It is also possible that strains of the virus that are resistant to AVs may emerge and reduce the effectiveness of the available antiviral drugs dramatically. The calculations presented here have not taken the possibility of the emergence of antiviral resistance into account. The impact of a strategy that relies heavily on the use of antiviral drugs for prophylaxis could be greatly reduced if antiviral resistance develops, if the resistant strain is also highly transmissible.
The feasibility of the timely use of AVs for prophylaxis decreases as R0 increases, because the amount of contact tracing required becomes too onerous.
ii Further work neededIt is necessary to design studies that are able to estimate the effectiveness of antiviral drugs against the emerged pandemic influenza virus during the early stages of a local epidemic. These studies must be simple so that they are feasible during the hectic early stages of the pandemic.
In our work we have not distinguished between different types of cases. Treatment may avert serious illness or even death. There is then a need to assess whether antiviral drugs should be used for treatment or prophylaxis, with respect to the incidence of severe illness or mortality.
We need to develop alternative strategies for the use of antiviral drugs in the event that the virus develops resistance to them.