  Objectives: Re-infection after treatment for Chlamydia trachomatis or
Neisseria gonorrhoeae reduces the effect of control interventions. We explored
the impact of delays in partner treatment on the expected probability of
re-infection of index cases using a mathematical model. Methods: We used
previously reported parameter distributions to calculate the probability that
index cases would be re-infected by their untreated partners. We then assumed
different delays between index case and partner treatment to calculate the
probabilities of re-infection. Results: In the absence of partner treatment,
the medians of the expected re-infection probabilities are 19.4% (interquartile
range (IQR) 9.2-31.6%) for chlamydia and 12.5% (IQR 5.6-22.2%) for gonorrhoea.
If all current partners receive treatment three days after the index case, the
expected re-infection probabilities are 4.2% (IQR 2.1-6.9%) for chlamydia and
5.5% (IQR 2.6-9.5%) for gonorrhoea. Conclusions: Quicker partner referral and
treatment can substantially reduce re-infection rates for chlamydia and
gonorrhoea. The formula we used to calculate re-infection rates can be used to
inform the design of randomised controlled trials of novel partner notification
technologies like accelerated partner therapy.
