Overview

• Researchers randomly assigned 249 adults with early syphilis at 10 U.S. sites to receive either one 2.4 million unit injection of benzathine penicillin G or three weekly injections.
• A serologic response at six months occurred in 76% of the single-dose group versus 70% of the three-dose group, a difference that was not statistically significant, including among participants with HIV.
• Safety monitoring recorded one participant who developed signs of neurosyphilis shortly after starting therapy and was excluded, and three serious adverse events judged unrelated to the drug.
• Syphilis cases in the United States exceeded 209,000 in 2023, and benzathine penicillin G is currently being imported to address a nationwide shortage.
• NIAID officials said the data support a potentially simpler approach, though effectiveness in late-stage disease or neurosyphilis remains unproven and treatment guidelines have not changed.