单选题 In 1976 more than 500 people contracted an autoimmune disease called Guillain - Barresyndrome after receiving swine - flu shots in response to a small outbreak in Fort Dix, N. J. Some people understandably fear a repeat of that tragic episode, However, vaccine, production techniques have changed since then. Today, vaccines are highly purified to eliminate any potential contaminants. In addition, scientists use only selected viral proteins in the shots, not the entire virus, as they did in the 1970s. "The public is comparing this vaccine to the 1976 swine--flu vaccine," says CDC spokesperson Abbigail Tumpey. "In fact, the best comparison is to the seasonal vaccines of the last ten years. "
Nowadays ,vaccines are highly purified to

• A. remove people's fear for vaccine.
• B. avoid repeating the tragic episode in 1976.
• C. get rid of any possible contaminants.
• D. improve vaccine -production techniques.