Pre-cum (pre-ejaculation) can hold a small amount of HIV. Pre-cum is the clear liquid that comes out of the penis before men ejaculate. There is less HIV in pre-cum than there is in semen, but it is still present. This means that the withdrawal or ‘pull-out’ method is not a reliable way to prevent HIV being passed on.

The risk of getting HIV from sex can vary, depending on a number of factors. Some of these are related to the type of sex you are having, for example anal and vaginal sex both have a higher risk of HIV transmission than oral sex. Other factors are related to the health of the individual, for example if you have an STI, your risk of getting HIV increases. One of the reasons for this is that many STIs create tears in the skin of your genitals that can provide an easy entry point for HIV. Similarly, if someone has only recently acquired HIV, they are much more likely to pass it on. This is because their viral load will be high in these initial stages of infection. In contrast, if you are adhering well to treatment, the risk of you passing on HIV becomes significantly smaller and eventually zero when you become undetectable.
 

While it’s good to know what factors might increase someone's risk of passing on or getting HIV, ultimately the best way of managing your risk of getting HIV is to use protection such as condoms and PrEP.

There is no vaccine to stop you getting HIV. To avoid getting HIV, you need to use a HIV prevention method like condoms or PrEP and avoid sharing injecting equipment. PrEP is a pill that can stop people from getting HIV even when they have sex without a condom with someone with HIV. PrEP is very effective at preventing HIV but isn't a vaccine, because you must keep taking PrEP to be protected. Once you stop taking PrEP, you're no longer protected from getting HIV.

A long-acting injectable PrEP that will protect you for a longer period of time (without you having to remember it everyday) was approved for use in the USA in early 2022. Researchers are trying to find a way to vaccinate against HIV.