As yet it has proved practically impossible to produce a vaccine against gonorrhoea because gonococci provoke only a very limited immunological response in humans. At one time, treatment with penicillin was very successful. Although mildly penicillin-resistant gonococci had been encountered, until recently none had been found which was able to break down the antibiotic and thus become almost completely insensitive to the drug. However, during the last few years, gonococci which can destroy penicillin have been encountered. As penicillin was the drug of choice for gonorrhoea, this development has exacerbated what the World Health Organization admits to be a global epidemic wildly out of control in many countries.