Thank you for writing to ATD.
The Hepatitis B vaccine is made of the HBsAg. This is an antigen that produces immunity to the Hep B virus.
You will need 3 doses to get immunity. You need to take all 3 doses of Hep B vaccine to ensure that the person develops immunity to Hep B.
Taking just 1 dose may not help you as you may not develop immunity at all. You need to wait for 1 to 4 months after the vaccination to develop immunity.
The immunity will be lifelong from then on and you need not worry.
Wishing you good health.
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