What is the third hepatitis B vaccine dose?

The third hepatitis B vaccine dose completes a vaccine course and helps build protection against future infection. It is given according to the schedule recommended for your age, health situation, and vaccine product. Missing the planned date usually does not mean the course must start again; a clinician can advise when to continue.

Earlier doses introduce the immune system to hepatitis B surface proteins, while a later dose reinforces immune memory. The schedule is designed to provide a dependable opportunity for protection, but the exact interval can differ. People with certain immune conditions, kidney disease, or occupational exposure may need a tailored plan or a follow-up blood test.

Check your vaccination record and take it to the appointment. Tell the vaccinator about a previous severe reaction, a current fever, pregnancy, immune-suppressing treatment, or a condition affecting the immune system. After the injection, mild soreness or tiredness can occur; rest, fluids, and a cool compress may help. Read more about [Hepatitis B Vaccination](/treatments/preventive-care-and-vaccination/hepatitis-b-vaccination/).

Seek emergency help for trouble breathing, facial or throat swelling, widespread hives, collapse, or severe dizziness after vaccination. Contact a clinician for a persistent high fever, worsening symptoms, or concerns about a delayed dose. Vaccination prevents infection; it does not treat an infection that is already present, so testing may be needed after a significant exposure.

Ask whether your schedule is complete, what to do if the appointment was delayed, and whether your health history changes the plan. Ask if household or sexual contacts need vaccination and whether a [Liver Function Test](/treatments/diagnostics-and-screening/liver-function-test/) or hepatitis B test is appropriate.