Hepatitis B: sexual transmission, testing and vaccination

What is hepatitis B?

Hepatitis B is a liver infection caused by the HBV virus. WHO estimates that 240 million people were living with chronic hepatitis B worldwide in 2024, with 1.1 million deaths a year, mostly from cirrhosis and liver cancer. Only 27% of infected people know it.

How is it transmitted?

HBV is far more infectious than HIV. It spreads through body fluids: blood, semen, secretions, and even saliva when there are cuts or sores (WHO). Hépatites Info Service specifies that it is transmitted:

• during anal sex, for both partners;
• during oral sex;
• during practices involving bleeding (fisting without gloves, shared lube);
• through shared, undisinfected toys;
• through shared injecting or snorting equipment (straws, syringes).

What are the symptoms?

Often none. Sometimes acute hepatitis: jaundice, dark urine, tiredness, nausea, stomach pain. In adults, according to WHO, infection becomes chronic in fewer than 5% of cases; otherwise the body clears it. Unmonitored chronic hepatitis B can damage the liver over years.

How is it tested?

With a blood test (HBs antigen and antibodies), which tells you whether you are infected, have recovered, or are vaccinated. It is part of the CeGIDD check-up and of France’s free “Mon test IST” for under-26s.

The vaccine: the best protection

• According to WHO, it offers close to 100% protection, for at least 20 years and probably for life.
• Sexosafe says 3 injections are needed, after which protection lasts for life, with no booster.
• It is recommended for men who have sex with men and free at CeGIDD clinics.
• It is required before starting PrEP if you are not immune.

If you were vaccinated as a child you are probably protected: a blood test can confirm it.

Chronic hepatitis B and PrEP

The drugs in oral PrEP also act against hepatitis B. Sexosafe insists: if you have chronic hepatitis B, never stop PrEP without medical advice, as it could trigger a hepatitis flare.

Treatment

Acute hepatitis B usually clears on its own. The chronic form is treated with antivirals (tenofovir, entecavir according to WHO), which slow progression to cirrhosis and cancer. Regular follow-up is needed.

Recent exposure?

If you’re not vaccinated and had a risky contact (infected partner, blood), see a doctor quickly: immunoglobulins and early vaccination may be offered, as with PEP.