I think it escalated about 10-15 years after that. Then it seemed to taper off somewhat; but then came back with a vengeance within the last three or so years. Maybe it’s due to more people seeking treatment.
Actually, the rate of cases of syphilis was actually higher in the 1940's (especially) and overall (with exceptions) decreasing until 2006 when it began an overall steady increase, yet the historical context of the former included aspects such as increased testing and diagnosis, soldiers returning from war, but with increased effective treatment with penicillin in the 1940s onward leading to a large decrease in transmission, and overall steady decrease in infection rates despite the increased % of teens to middle ages from the 60's to mid 80s. Which, after a brief increase in 1987 to 1992, saw an overall steady and significant decrease until about 2012 (but nowhere close to the 1940's). After which an overall steady rise occurred, leading to a rate of 53.2, which has not been seen since 1919 and 1966. In contrast, gonorrhea saw unprecedented high rates from 1970 to 1990 when they began to overall steadily fall to a rate of 98.1 in 2009, only to rise to 214, not seen since 1991. (https://www.cdc.gov/std/statistics/2021/tables/1.htm) All of which is despite an increasingly aged population and better testing and treatment.)
The original poster said STD (which is not limited to syphilis); and, of course, his criteria was for the post-Vietnam era. That is what I responded to.