Gonorrhea and syphilis are the two most common STDs that require a shot as part of their standard treatment. Both are treated with a single injection visit in most cases, though the specific medication and approach differ. Several other sexually transmitted infections also involve injections, either for prevention or for long-acting protection against HIV.
Gonorrhea: A Single Injection
Gonorrhea is treated with a single shot of an antibiotic called ceftriaxone, injected into a muscle (usually the buttock or thigh). The standard dose is 500 mg for people weighing under 330 pounds, and 1,000 mg for those above that weight. There are no oral antibiotics currently recommended as a first-line gonorrhea treatment. The bacteria that cause gonorrhea have developed resistance to nearly every class of oral antibiotic over the past few decades, making an injectable antibiotic the only reliable option.
This is a one-time injection. You don’t need to return for follow-up shots. However, the CDC recommends retesting three months after treatment to check for reinfection, which is common, especially if a sexual partner wasn’t treated at the same time.
Syphilis: One Shot for Early Stages
Syphilis is treated with a penicillin injection, and it has been for over 70 years. For primary or secondary syphilis (the early stages), a single shot of 2.4 million units of long-acting penicillin G resolves the infection. The injection goes deep into the buttock or thigh muscle and is given at a slow, steady rate because the medication is thick.
If syphilis has progressed to a later stage, or if retreatment is needed, the protocol extends to three weekly injections of the same dose. People with a penicillin allergy can take a 14-day course of oral antibiotics instead, though penicillin remains the preferred treatment, particularly during pregnancy.
The syphilis shot is known for being uncomfortable. The medication is a dense suspension, and the needle used is larger than what you’d encounter with a flu shot. Some soreness at the injection site for a day or two afterward is normal.
HPV Vaccine: Prevention Through a Shot Series
HPV (human papillomavirus) isn’t treated with a shot, but it is prevented with one. The vaccine protects against the strains most likely to cause genital warts and cervical, throat, and anal cancers. The number of doses depends on when you start:
- Ages 9 through 14: Two doses, spaced 6 to 12 months apart.
- Ages 15 through 45: Three doses over six months (the second at one to two months, the third at six months).
The vaccine is most effective when given before any exposure to HPV, which is why it’s routinely recommended for preteens. But adults up to age 45 can still benefit, particularly if they haven’t been exposed to all the strains the vaccine covers.
Hepatitis B Vaccine: A Multi-Dose Series
Hepatitis B spreads through sexual contact, shared needles, and from mother to child during birth. There’s no cure once you have a chronic infection, but vaccination prevents it entirely. Most versions of the vaccine require three shots spread over several months. A newer formulation approved for adults 18 and older requires only two doses.
Most people in the U.S. received this vaccine as infants. If you’re unsure whether you were vaccinated, a blood test can check for immunity, and you can complete the series as an adult if needed.
Injectable HIV Prevention
HIV itself isn’t treated with a shot in the way gonorrhea or syphilis are, but there are now injectable options for prevention. Long-acting cabotegravir is an injection given every two months (after two initial monthly doses) that prevents HIV infection. It’s an alternative to taking a daily pill for people at higher risk of exposure.
A newer option, lenacapavir, takes this further. After an initial loading phase, it requires an injection only once every six months. Both are forms of PrEP (pre-exposure prophylaxis) and are given as shots in a clinical setting.
Mpox Vaccine
Mpox, which can spread through close skin-to-skin contact including sexual contact, is preventable with the JYNNEOS vaccine. It’s a two-dose series with the second shot given four weeks after the first. It’s primarily recommended for people at higher risk of exposure.
What to Expect at Your Visit
If you’re being treated for gonorrhea or syphilis, the injection itself takes only a few minutes. Gonorrhea treatment is typically painless beyond a brief pinch. The syphilis shot tends to be more noticeable because the medication is thicker and requires a slower injection. Both are given in the buttock or thigh. You can usually return to normal activities immediately, though mild soreness at the injection site is common for a day or two.
For gonorrhea and chlamydia (which often occur together), you may receive a shot for the gonorrhea and an oral antibiotic for the chlamydia during the same visit. If you test positive for syphilis, your provider may also test for HIV, since the two infections share risk factors and can affect each other’s progression. Regardless of which STD required the shot, retesting at three months helps catch any reinfection early.