STI Rates by Age: What 2025 CDC Data Shows

CLINICALLY REVIEWED BY • Conrad Shakes, MSN FNP-BC • Nurse Practitioner

REVIEWED FOR MEDICATION AND PRODUCT SAFETY ACCURACY BY • Allyx, PharmD • Licensed Pharmacist

STI rates by age are not evenly distributed — the data make that clear. A 2021 NIH model estimated 26.2 million new STI infections in the United States in 2018 alone. The CDC's national surveillance report consistently shows that some age cohorts carry a disproportionate share of that burden — and that the distribution matters for condom use.

This blog breaks down what CDC, NIH, and WHO surveillance data show about STI risk across four age cohorts: 15 to 24, 25 to 34, 35 to 44, and 45 and older. Each section uses sourced statistics. Where condom retention connects to the data, that connection is explained — without overstating what Slip Guard can or cannot do.

• Which age group the data shows carries the heaviest STI burden — and why the number is almost certainly an undercount

• The cohorts most often left out of STI conversations, and what CDC surveillance shows about their real-world risk

• Why condom retention is a consistent-use issue that applies across every age group — not just the young

A common assumption is that STI risk naturally declines once people move out of the 15-to-24 window. The data do not fully support that. The 25 to 34 age group still sees elevated rates for chlamydia and gonorrhea, and syphilis burden has been shifting notably into this cohort in recent years.

Chlamydia remains a major factor. In 2024, CDC provisional data counted more than 1.5 million reported chlamydia cases nationally — down from the prior year, but still substantial [Source: CDC]. The 25 to 34 group accounts for a significant share of those reported cases, particularly among women. The testing gap that understates the 15-to-24 burden is just as real here — people in this cohort often test less regularly than their younger peers, especially outside of routine prenatal or general health checkups.

Gonorrhea rates in the 25-to-34 group sit below the 15-to-24 peak but remain elevated. In 2024, CDC provisional data showed 543,409 total gonorrhea cases nationally, with cases among men and women both declining from 2023 but still well above levels from a decade ago [Source: CDC]. The 25-to-34 age band represents a large portion of the sexually active population, and their rates reflect that exposure.

Syphilis in this group is a more pressing concern. CDC's provisional 2024 data show total syphilis cases are still 42 percent higher than in 2020, even after a national year-over-year decline [Source: CDC]. Women in their mid-to-late 20s and early 30s have seen particular increases in syphilis categories tracked by CDC. Women's early non-primary non-secondary syphilis cases reached 14,061 in 2024, up 80 percent since 2020 [Source: CDC]. The 25-to-34 window is no longer a low-risk window by any measure the surveillance data shows.

Sexual health messaging is heavily aimed at people under 30. People in the 35-to-44 range often fall outside the frame of those campaigns — and the data suggest that matters. STI rates in this group are lower than the 15-to-24 peak, but they are not zero, and they are not insignificant. CDC tracks primary and secondary syphilis rates specifically among women aged 15 to 44 at the county level, which itself signals that this age group warrants monitoring — not just the youngest cohort [Source: CDC, County-level Syphilis Data].

Condom use often drops in this window. People in their late 30s and early 40s may be in long-term partnerships or may perceive their STI risk as low based on life stage rather than actual exposure. Those perceptions do not always track with the data. STIs can be asymptomatic and go undetected across years — NIH notes that people can have an STI with no symptoms and pass it on without knowing [Source: NIH/NICHD]. A gap in testing or a reduction in consistent condom use both increase the chance that an infection circulates undetected in this group.

Where Slip Guard connects to this cohort is straightforward: when condoms are used, they need to stay in place to do their job. CDC says incorrect or inconsistent condom use can lead condoms to break, slip, or leak [Source: CDC]. That statement applies equally to a 22-year-old and a 40-year-old. Condom retention is not an age-segmented problem — it is a physics and fit issue that occurs regardless of the user's age or experience. For people in the 35-to-44 group who do use condoms, making sure the condom stays seated is part of making the protection work.

The 45-and-older cohort is the group where the gap between perceived risk and actual risk may be the widest. Several factors converge here: the assumption that STI risk largely belongs to younger people, lower rates of routine STI testing, and the reality that some people in this cohort are entering new sexual partnerships — through divorce, re-partnering, or the growing reach of dating apps — without the same protective habits they may have had earlier in life.

Post-menopause is a specific point of confusion. For women past menopause, pregnancy is no longer a concern — which can shift the perceived need for condom use. But condoms protect against STIs, not just pregnancy. CDC notes that birth control methods like the pill, patch, ring, and IUD are effective at preventing pregnancy but do not protect against STIs or HIV [Source: CDC]. The same logic applies post-menopause: the absence of a pregnancy concern does not change the STI transmission dynamic of condomless sex.

Syphilis data are particularly telling here. Total syphilis cases in the United States were still 42 percent above 2020 levels in 2024 even after a recent national decline [Source: CDC]. WHO says that more than 1 million curable STIs are acquired every day worldwide among people ages 15 to 49, with the majority of those infections asymptomatic [Source: WHO]. The 45-to-49 portion of that WHO window alone represents tens of millions of adults globally. The idea that this age group is outside the risk picture is a perception gap, not a data-supported conclusion.

The CDC data on STI rates by age make one thing consistent across all four cohorts: where condoms are used correctly and consistently, protection improves. Where they are not, exposure risk rises. WHO has modeled that increased condom use since 1990 has averted approximately 117 million new HIV infections globally [Source: WHO]. That is not a theoretical figure — it reflects the real-world impact of condom use at scale. The same mechanism applies to bacterial STIs like chlamydia, gonorrhea, and syphilis.

The catch is what "used correctly" means in practice. CDC says that incorrect or inconsistent condom use can lead condoms to break, slip, or leak [Source: CDC]. And CDC adds that STIs or HIV can spread from a single sex act with an infected partner when condoms are used incorrectly or inconsistently [Source: CDC]. Those two statements together frame the stakes: using a condom is the right call, and it has to work correctly to provide the protection it is capable of providing.

Condom slippage is part of that picture. In one NIH study, condom breakage or slippage was reported during 6.0 percent of condom uses, and partial condom use — where the condom came off before sex ended — was reported in 12.5 percent of uses [Source: NIH/PMC]. Those rates apply to every age group that uses condoms. Slip Guard addresses the retention piece of that equation: it sits below the condom base and helps keep it seated during use. It does not replace correct sizing, application, or the condom itself — those basics still do the heavy lifting. But for people who have the right basics in place and still deal with the condom shifting, Slip Guard adds the anchor point the base ring alone does not have.

The CDC's message on age and STI risk applies in the same direction to condom use: the data does not segment who needs to use a condom correctly by age. Consistent and correct use is the standard regardless of where someone falls in the 15-to-49 range — or beyond.

STI rates by age tell a more layered story than most people expect. The 15-to-24 group carries the largest documented burden — but that does not mean the 25-to-34, 35-to-44, or 45-and-older groups are in a low-risk bracket. What the surveillance data shows is that risk does not neatly end at a birthday, that asymptomatic infections drive a significant undercount across every cohort, and that condom use is the primary tool the evidence keeps pointing back to. Where condoms are used correctly, consistently, and in a way that keeps them seated, the protection they provide is real. STI rates by age are what they are partly because that combination of factors does not happen as often as it could. The data is the data — and it points the same direction regardless of generation.

• People ages 15 to 24 account for roughly 45 to 48 percent of new STI infections — and the true number is higher than reported cases show.

• Ages 25 to 34 and 35 to 44 still carry real and documented STI burden — syphilis in particular has not spared these groups.

• Consistent and correct condom use — including keeping the condom seated — is the factor that runs through every age cohort in the CDC's own guidance.