The symptoms of hepatitis A appear no earlier than 60 days after a person has been infected  In a test of a hepatitis A vaccine, 50 people received the vaccine and 50 people received a harmless placebo
Although some people from each group eventually exhibited symptoms of hepatitis A, the vaccine as used in the test is completely effective in preventing infection with the hepatitis A virus
Of the people who developed symptoms of hepatitis A, those who received the vaccine recovered more quickly, on average, than those who did not.