Помогите в математике :-)

Вот статья:
http://www.eurekalert.org/pub_releases/2012-05/uotm-hvd051712.php

Я чота туплю и не понимаю как вывели результат в 43%?
The researchers found that patients who received the vaccination had an estimated recurrence rate of 10.3% compared to 18% in the control group at a median follow up of 22 months. This represented a 43% reduction in the risk of recurrence.