A simulation model to evaluate influenza vaccination strategies

Over the period 1967-1989 yearly epidemics in the Netherlands have caused on average 430 deaths with influenza as the primary cause. In addition, influenza contributed to excess mortality by other causes, such as cardiovascular and respiratory diseases. This excess mortality was estimated at another 1120 yearly deaths, mostly in older people. Current Dutch public health policy favors influenza vaccination for risk groups, e.g. patients suffering from a number of chronic diseases, such as coronary heart disease, cerebro vascular accidents and diabetes mellitus. Is has also been suggested, however, that vaccination of all older people would be advisable. To support health policy decision making with regard to influenza vaccination we developed a compartmental simulation model which simulates different vaccination strategies. A first set of calculations assuming a simplified scheme of acquiring and losing immunity indicates that influenza-related mortality decreases with 240 persons or almost by a factor three, when vaccinating every person of 60 years or older, as compared to the current policy of vaccinating only the groups at risk mentioned above. However, to achieve this result more than three and a half million people should be vaccinated in contrast to the half million people that must be vaccinated when only vaccinating persons suffering from IHD. These outcomes show this simulation models can be used for decision making in chossing a vaccination strategy.