World A Daily Pill to Prevent S.T.I.s? It May Work, Scientists Say. July 18, 2024APOORVA MANDAVILLIComments Off on A Daily Pill to Prevent S.T.I.s? It May Work, Scientists Say. A common antibiotic, doxycycline, greatly reduced cases of syphilis, gonorrhea and chlamydia when taken every day, a study found.