What are Sexually transmitted infections (or STIs)?

Sexually transmitted infections (or STIs) are infections that can be caught or passed on when you have unprotected sex, or close sexual contact, with another person who already has an STI. Using a condom for all types of sex is the best way to avoid STIs and HIV. Vaccines can prevent certain STIs like genital warts and hepatitis B. Reducing the number of sexual partners you have and not mixing alcohol, drugs and sex also means you’re less likely to get infected.