Does contraception protect against STIs: ten myths, ten facts

01The pill prevents pregnancy, not STIs

Every hormonal method works the same way: it stops ovulation, thickens cervical mucus, or both. None of that does anything to a bacterium or a virus. The pill, the injection, the implant, the patch, the ring and the hormonal IUS all sit at zero for STI protection.

This is the most common misunderstanding we hear at the desk, and it's not a silly one. Both things are called contraception, and both are about sex. But one is about pregnancy and the other is about infection, and they need different tools.

02Only barrier methods reduce STI risk

A barrier method puts something physical between two people: an external condom, an internal condom, or a dental dam for oral sex. Those are the only methods on the list that reduce STI transmission, because they're the only ones that stop fluids and limit skin contact.

If you're on the pill, the injection or an implant and you want STI protection too, that means condoms as well. Health services call this dual protection. It's the normal thing to do, not an extra.

03One condom, used correctly, is the correct method

Two condoms rub against each other. Friction is exactly what makes latex tear, so doubling up makes a break more likely, not less. The same goes for an external and an internal condom at the same time.

One condom, put on before any contact and kept on until the end, is the whole method. The checklist further down covers the details that actually matter.

04Many STIs have no symptoms. Testing is the only way to know

Around 70% of women with chlamydia have no symptoms. Most people with HPV never know. Herpes, Mycoplasma genitalium, ureaplasma and early syphilis are all routinely silent. In our lab, roughly 1 in 4 people who test with no symptoms at all have at least one infection.

Feeling fine tells you that you feel fine. It doesn't tell you anything about what's there. A PCR panel does: the 9-target Medium is R1,580, no doctor's referral, results in 5 to 7 working days.

05Condoms reduce your risk, but don't eliminate it

Used consistently and correctly, condoms cut HIV transmission by around 80%, and they substantially reduce chlamydia, gonorrhoea and trichomoniasis. That's a very good number. It isn't 100%, and for some infections it's lower.

HPV, herpes and syphilis spread by skin-to-skin contact, including skin the condom doesn't cover. A condom still reduces the risk of all three, roughly halving HPV in one large study, but it can't cover what it doesn't cover. Regular testing still matters, condoms or not.

06A large South African trial found no meaningful difference between the injection, the copper IUD and the implant

For years there was a real scientific worry that the three-monthly injection might raise a woman's risk of acquiring HIV. Because the injection is the most used method in South Africa, this mattered enormously here.

So it was tested properly. The ECHO trial randomised 7,829 women in South Africa, eSwatini, Kenya and Zambia to the injection, the copper IUD or the implant, and followed them. Published in The Lancet in 2019, it found no substantial difference in HIV incidence between the three. What it did find was that HIV incidence was high in all three groups, which is the actual message: contraception isn't HIV prevention, whichever method you choose.

07Spermicide doesn't protect against STIs, and frequent use can raise HIV risk

The common spermicide, nonoxynol-9, was once hoped to work against HIV and other infections. It doesn't. Worse, used often it irritates the lining of the vagina and rectum, and that irritation makes HIV easier to acquire, not harder. The World Health Organization has advised against using it for STI or HIV prevention since 2001.

If a condom is lubricated with spermicide, it's the condom doing the protecting, not the spermicide.

08Withdrawal gives no STI protection at all, and it's unreliable for pregnancy too

Infections transmit through contact and through fluid released long before ejaculation. Pulling out changes nothing about either. As contraception it fails often, because timing is hard and pre-ejaculate can carry sperm.

It's the method people fall back on when there's nothing else to hand, which is exactly the situation a condom in the drawer is for.

09PrEP protects against HIV only

PrEP is excellent at what it does, and what it does is prevent HIV. It has no effect on chlamydia, gonorrhoea, syphilis, herpes, HPV, Mycoplasma genitalium or anything else.

In a South African study of PrEP users given lab tests, about 1 in 4 women and 1 in 5 men had chlamydia. If you're on PrEP, condoms still do a job PrEP can't, and a PCR panel every few months fits alongside your PrEP check-ins.

10Gonorrhoea, chlamydia, syphilis, herpes and HPV all pass through oral sex

Throat infections are usually silent and a genital swab won't find them. A condom for oral sex on a penis, and a dental dam for oral sex on a vulva or anus, reduce the risk. Most people don't use them, which is why we add a throat swab to any sexual health panel at no extra charge. If the exposure was oral, ask for it.