A single dose of doxycycline, a broadly used antibiotic, taken after intercourse halved the incidence of chlamydia and early syphilis amongst homosexual and bisexual males and transgender ladies in San Francisco, metropolis well being officers introduced on Monday. The findings supplied a glimmer of hope amid a rising tide of sexually transmitted infections nationwide.
The technique known as doxy-PEP, shorthand for doxycycline post-exposure prophylaxis. In San Francisco, homosexual and bisexual males and transgender ladies who had a historical past of S.T.I.s or a number of intercourse companions got a provide of the antibiotic and requested to take two 100-milligram tablets inside 72 hours of unprotected intercourse.
New instances of chlamydia and early syphilis — however not gonorrhea — dropped over the course of a couple of yr. The outcomes have been introduced on the Convention on Retroviruses and Opportunistic Infections in Denver.
“It’s not refined, it is rather quick and we’re seeing the start of it, not the top,” Dr. Hyman Scott, a medical director on the San Francisco Division of Public Well being, mentioned in an interview. “That is what we would like for S.T.I. prevention.”
Methods to stem S.T.I.s are sorely wanted.
Syphilis, as soon as practically eradicated in the US, has reached the best fee of recent infections recorded since 1950, the Facilities for Illness Management and Prevention reported in January. Left untreated, syphilis can injury the center and mind and trigger blindness, deafness and paralysis.
Charges of chlamydia remained flat nationwide in 2022, in contrast with the quantity in 2021, however at practically 1.7 million instances, infections have been widespread. (Gonorrhea instances decreased in 2022, however specialists cautioned that the development might need been the results of a lower in testing.)
“These knowledge are merely numbers of S.T.I. instances at totally different time factors however make me really feel hopeful that doxy-PEP could possibly scale back S.T.I.s at a inhabitants degree,” Dr. Ina Park, an S.T.I. professional on the College of California, San Francisco, mentioned of the brand new outcomes. She was not concerned with the work.
The proof up to now helps the case for doxycycline use solely in homosexual and bisexual males and transgender ladies. Earlier research have proven {that a} single dose of doxycycline taken inside 72 hours of unprotected intercourse considerably cuts the danger of S.T.I.s in these teams.
“The vast majority of S.T.I.s in the US happen in cisgender ladies,” mentioned Dr. Jonathan Mermin, director of the Nationwide Middle for H.I.V., Viral Hepatitis, S.T.D. and TB Prevention on the C.D.C.
“Research of whether or not doxy-PEP works in cisgender ladies must be carried out as rapidly as attainable,” he mentioned.
In October, the C.D.C. launched draft pointers for doxy-PEP. It is going to problem its closing suggestions within the subsequent few months, Dr. Mermin mentioned.
However, prompted by early medical trial outcomes, the San Francisco Division of Public Well being — a pioneer within the struggle towards H.I.V. and S.T.I.s — started recommending doxy-PEP a yr earlier than the company’s draft pointers have been printed.
Metropolis officers tracked month-to-month charges of chlamydia, gonorrhea and early syphilis earlier than and after the introduction of doxy-PEP in November 2022. In addition they in contrast the numbers with the speed of infections in cisgender ladies.
Over a 13-month interval, new instances of chlamydia and early syphilis throughout the town dropped by 50 p.c, in contrast with the anticipated numbers. Charges of gonorrhea didn’t change considerably.
In contrast, instances of chlamydia in cisgender ladies steadily elevated. Metropolis well being officers plan to investigate the numbers over an extended interval to substantiate the downward development.
“The truth that we didn’t see declines in S.T.I.s in different populations not beneficial for doxy, particularly cis ladies, strengthens the conclusion that the decline in chlamydia and early syphilis instances is said to doxy-PEP rollout,” mentioned Madeline Sankaran, an epidemiologist on the San Francisco Division of Public Well being who introduced the findings.
A separate research discovered that S.T.I. charges dropped regardless of a rise in sexual companions, situations of intercourse with out condoms and group intercourse amongst individuals taking doxy-PEP. Greater than 75 p.c of these supplied the tablets reported taking them after intercourse with out condoms, the researchers mentioned.
Whereas the outcomes are promising, Dr. Mermin cautioned, they could have been skewed by the 2022 outbreak of mpox, beforehand often known as monkeypox, throughout which high-risk teams voluntarily curtailed their sexual exercise. There was additionally a restricted impact on charges of gonorrhea, he added.
Dr. Mermin mentioned decreasing S.T.I.s nationwide would require making certain that the strategy is used within the South and in rural areas, and in Black and Latino populations which might be at excessive danger.
“No software, irrespective of how highly effective, will forestall infections if it doesn’t attain the individuals who want it most,” he mentioned.
There was some concern concerning the emergence of antibiotic resistance with widespread use of doxycycline, however the restricted knowledge obtainable recommend that the strategy doesn’t considerably enhance resistance in individuals who take it, Dr. Mermin mentioned. The C.D.C. and others are monitoring the developments, he added.
If additional evaluation confirms doxy-PEP’s potential, Dr. Park mentioned, she might foresee intercourse celebration hosts providing the tablets, a lot as clinics now provide condoms.
Maybe the antibiotics could be in a jar with an indication saying, “Take two in your method out the door,” she mentioned. “That’s the place I see this going.”
