This is not an accurate thing to say. Side effects are less than are caused by most prescribed drugs.
It MAY be that those of us who had the full series of immunizations as kids may have some partial immunity. This could mean we would get less sick, or might be more resistant to even catching it at all. This could become important if smallpox does appear before enough doses of vaccine are available for the entire US public. I for one would be willing to forgo a vaccine for my unimmunized children.
Most prescribed drugs are taken by a small subset of the population who are already ill, whereas vaccinations are usually taken by the whole population usually when well. Assuming a death rate of 1:1,000,000 (the historical rate for the existing vaccine) vaccinating everyone in the wolrd would kill 6,000 people (more than died in the World Trade Center). There are also inflamations of the brain that can cause permanent brain damage. If there were a deliberate release of smallpox, the risks of the current vaccine would be justified. Also, the smallpox vaccine does not give permanent immunity to the disease, making additional vaccinations neccessary in order to maintain adequate antibody levels. I have not seen statistics on complications from initial vaccinations versus boosters.
The statistics about complications are old because no country has routinely vaccinated against smallpox in over twenty years. The only population in this country that gets vaccinated today is the military, and they tend to have a fairly young and healthy population to start with. The general population in this country includes a considerable number of people with compromisede immune systems who in the past would not even still be living but today are able to. These include AIDS patients, cancer chemotherapy patients, organ transplant recipients, etc.