Still,medical experts say people should not take aspirin for disease prevention without first talking to a doctor.

VOA: special.2009.10.20

One can stop spread of disease through a community without being 100% effective in each person who gets the vaccine.

疫苗能够遏制疾病在整个社区中传播,虽然对于每个人来说它并非百分之百有效

耶鲁公开课 - 生物医学工程探索课程节选

People infected with this form may develop the disease over many years without any major symptoms.

VOA: special.2010.01.04

Some people without celiac disease say they feel better when they avoid gluten.

VOA: special.2010.11.16