Is it possible to have bad adverse reactions to the smallpox vaccine if the government gives it out for bioterrorism?

Yes: There is a very small , but real risk to this vaccine of developing a fatal case of smallpox from the vaccine.But in an epidemic situation, this risk is far less than naturally becoming sick. Hopefully this scenario will never occur.

Yes: More robust reactions are seen more commonly in those not previously immunized.

Smallpox Vaccination: Smallpox vaccine mild rxn's include sore & red vaccination site, tender & enlarged axillary lymph nodes, low fever & feeling ill. More serious rxns occurred in 1,000 per million – vaccinia rash or toxic rash (Erythema multiforme). Extremely rare severe rxns: included Postvaccinal Encephalitis & Eczema Vaccinatum wi a death rate of 1 to 2 per million. So - yes adverse rxn's are possible.