<prompt> Phase 4 clinical trials is carried out:Before the marketing approval of a drugAfter a drug is marketedFor drugs used in rare diseaseFor drugs used in pediatric patients  <response>: A new drug vaccine is launched in the market after phase III RCT. Phase IV is Post marketing surveillance phase Is the longest phase in a clinical trial. Should be carried out life long minimum 10-25 years. Is done for finding long term side effects and rare side effects of the drug. 