There was a new study that just came out, that shows that vaccines are a great investment in terms of money savings due to later treatment of diseases for which a vaccine exists. These cost savings come in the form of not only medical treatment but loss of productivity due to the medical illness. In addition to the cost savings on the individual that receives the vaccination, there is also a cost savings associated with the community in which that individual lives due to reduces illness overall. The study looks at low to middle income countries and the economic effects that vacations have therein. Although any vaccine can cause side effects, generally the side effects are minimal compared to the benefits they bestow upon the patient. Serious vaccine side effects are experienced in very few people (as little as 1 in 100,000) and can include allergic reactions among other things.
The study is additional evidence that investing in preventative healthcare can make a difference, especially in countries where such diseases are more prevalent. Vaccines generally speaking are very economic to administer, when considering the cost of treatment of the particular diseases. Obviously some vaccines will have a better return on investment (ROI) than others (as some will even be negative in terms of ROI, based on this study), but the study is a good example of the overall benefit (at least economically) of vaccinations in a global environment.
One issue is that participation in vaccine programs in developing countries is still remarkably low (sometimes less than 10%, even when such vaccines are given freely); some countries have mandatory vaccines because of the value they are perceived to provide. Other countries like Australia are creating incentives to get their population vaccinated; for example they will not provide childcare subsidies to families who do not receive vaccines for their children.