Every single drug in the market has a side effect and before they are progressed to clinical trial phase they have to pass safety tests in animals first and the vaccine is deactivated before administering, so it cannot cause disease. 
Kila dawa iliyoko kwenye soko ina madhara yake na kabla ya kuifanya itimike kwenye tiba lazima kwanza uthibitike kuwa salama kwa wanyama kwanza na kisha inafanywa isifanye kazi kitaalam kabla ya kuanza kuitumia, ili isije ikasababisha ugonjw ahuo.