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We did a cohort analysis to estimate and compare incidence of VTE in users of the main OC preparations , and a nested case - control study to calculate the odds ratios of VTE associated with use of different types of OC , after adjustment for potential confounding factors .
 Disease: VTE; Chemical: OC; Disease: VTE; Chemical: OC
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Disease, Chemical 
Text: {0} 
Answer:
 Disease: VTE; Chemical: OC; Disease: VTE; Chemical: OC