I am suffering from prostatitis. my doctor prescribed me vibramycin (doxycycline) 100mg will it be helpful?

Yes : This antibiotic is used in genitourinary related infections and very effective against organisms such as chlamydia ...keep following up with your PCP .

Maybe: Prostatitis often responds to Vibramycin (doxycycline). It usually takes several weeks to completely treat the problem. Discontinuing the treatment prematurely will reduce the likelihood of its helping.

Most likely: Unclear to me if this was a documented infection or treated on high clinical suspicion, but Doxycycline or Vibramycin (doxycycline) is commonly used in acute prostatitis.