What should you know about the hepatitis B live vaccine?

Because it does not contain live hepatitis B virus, the vaccine cannot give you hepatitis B. It presents a surface protein so the immune system can prepare protective antibodies. Protection develops through the recommended schedule, which may differ by age, health needs and local guidance.

The vaccine prevents new infection; it does not treat an infection already present. A hepatitis B laboratory test may be appropriate when someone has had a possible exposure or belongs to a group advised to test. Fatigue or dark urine after an illness should be assessed rather than assumed to be a vaccine effect.

Tell the vaccinator about a previous serious allergic reaction to a vaccine, current illness, pregnancy, immune problems and medicines. Keep the appointment record and return for any doses in the recommended series. A sore arm, mild fever or tiredness can occur; ask the clinic how to manage symptoms safely.

If a dose is delayed, contact the vaccination service for a catch-up plan rather than restarting on your own. After a recent exposure, seek medical advice promptly because vaccination may be only part of the recommended response.

Seek emergency help for facial or throat swelling, wheezing, difficulty breathing, widespread hives, fainting, or sudden severe weakness after vaccination. Contact the clinic for a high or persistent fever, worsening illness, or symptoms that concern you.

Ask which schedule is recommended, whether you need testing first, what to do after a missed dose, and whether your health conditions change the plan. Ask how vaccination fits with testing or care after a possible exposure.