Condoms provide good protection from HIV, though apparently not as good as PrEP. Daily PrEP provides nearly perfect protection, reducing the risk of new HIV infections by 99% [1, 2, 3]. CDC has found that condoms, used consistently and correctly, reduce new HIV infections by 70% [4]. CDC also found there is no statistically significant difference between using condoms “sometimes” and using condoms “never.” Neither approach provides reliable protection from HIV [4].
PrEP does not protect you from STIs other than HIV, but condoms can. Condoms reduce the risk that you’ll contract gonorrhea, chlamydia, and trichomoniasis. Condoms can also provide protection from herpes, syphilis, and chancroid, but only if the condom fully covers the source of infection. Condoms only work when you use them. So, for example, if a sexual encounter includes both oral and anal sex, but you only use a condom for the anal sex, you can still contract STIs orally, including syphilis, gonorrhea, chlamydia, and herpes. [5]
The main reason that condoms don’t work better is that people don’t use them consistently. In fact, we know that most gay and bisexual men stopped using condoms long before PrEP. Between 1998 and 2001, a CDC study found that only 16% of MSM reported consistent condom use during anal sex with male partners [4]. In 2014, a Kaiser study found that only 25% of gay and bisexual men reported using condoms all the time [6]. In a major San Francisco PrEP program in 2015, 91% of consumers reported they were already having condomless sex [2]. The numbers are different in different studies, but they have one thing in common: most gay and bisexual men do not use condoms consistently.
Like all medications, PrEP only works if you take it. However, PrEP is “forgiving.” It still works even if you miss some doses. Studies show the risk of contracting HIV is 96% lower even if you take only 4 doses per week [1]. (Adherence was not great in early clinical trials when people did not know if PrEP worked or if the drug they were taking was real or placebo. In the real world, adherence has been much better, especially among people who believe they are at high risk for contracting HIV [2].)
PrEP provides nearly perfect protection from HIV, but no protection from other STIs. Condoms, used consistently and correctly, provide good protection from HIV and reduce the risk you’ll contract other STIs. Condoms only work if you use them and if they fully cover the source of any infection. Most major STIs can be transmitted during oral, anal, or vaginal sex.