Rebuttal
========


Dr. Schabas maintains that influenza vaccination is efficacious and cost-effective, but he provides no evidence for this. Dr. Schabas claims that vaccine “efficacy is between 70% and 90%,” but this is both wrong and misleading. Vaccine efficacy, as Dr. Schabas uses the term, is probably about 60% (not 70%–90%), and this refers only to the ability of a vaccine to produce antibodies effective against the virus. But this is not the important measure of vaccine efficacy. Instead, we should measure the ability of the vaccine to prevent clinical disease, in this case influenza. By this measure, vaccine efficacy is no greater than 25%.

Given that mass vaccination, even if it can be achieved, will only reduce the number of influenza cases by 25% at most, can it be cost-effective, as Dr. Schabas claims? Arguments for cost-effectiveness cited by Dr. Schabas are inferred from studies done in other countries with different systems of heath care delivery. There are no studies of the cost-effectiveness of vaccination in Ontario. In addition, given the dynamics of influenza epidemics, it is unlikely that the Ontario strategy will achieve any control over the spread of influenza in the community. To achieve such a goal would require vaccination of over 90% of the population, a target that is very unlikely to be achieved. 

The Ontario decision to implement mass influenza vaccination has little to do with influenza control. As clearly stated by the Ontario government, the aim is to ease pressure on emergency services during the “influenza season.” There is absolutely no evidence that universal vaccination has ever achieved such a goal.

I doubt that we will ever know the actual effect of this program and its cost-effectiveness, because it was not designed in a way that allows rigorous evaluation. Although I am tempted to applaud Ontario for its innovative spirit, I wonder whether the program should, instead, serve as a warning to other governments. The “let's see what happens” approach to public health should not be emulated.

## Footnotes

*   *Dr. Demicheli responds to Dr. Schabas:*