When is the second hepatitis B (HB) vaccination typically administered?

Timing of the Second Hepatitis B Vaccination

The second hepatitis B vaccination should be administered at least 1 month (4 weeks minimum) after the first dose. 1, 2

Standard Timing Schedules

For Infants Born to HBsAg-Negative Mothers

• First dose: At birth or by 2 months of age 1
• Second dose: At 1-2 months of age (minimum 4 weeks after first dose) 1
• Third dose: At 6 months of age 1

For Infants Born to HBsAg-Positive Mothers

• First dose: Within 12 hours of birth (with HBIG) 1
• Second dose: At 1-2 months of age 1
• Third dose: At 6 months of age 1

For Adolescents and Adults (Standard 3-Dose Series)

• Schedule: 0,1, and 6 months 2
• The second dose is given 1 month after the initial dose 2

Minimum Interval Requirements

The Advisory Committee on Immunization Practices establishes clear minimum intervals that must be respected: 1, 2

• Between dose 1 and dose 2: Minimum 4 weeks 1, 2
• Between dose 2 and dose 3: Minimum 8 weeks 1, 2
• Between dose 1 and dose 3: Minimum 16 weeks 1, 2

Grace Period Rule

• Doses administered ≤4 days before the minimum interval are considered valid and do not need to be repeated 2, 3
• Doses given more than 4 days early must be readministered 1

Management of Interrupted Schedules

If the second dose is delayed beyond the recommended timing, the series should never be restarted—simply continue where you left off. 1, 2, 3

• Administer the delayed second dose as soon as possible 1, 2
• Maintain the minimum 4-week interval from the first dose 1, 2
• The third dose should then follow at least 8 weeks after this delayed second dose 1, 2

This principle is based on immunologic memory, which retains the effect of previous vaccine doses even with extended intervals. 3

Special Vaccine Formulations

Heplisav-B (2-Dose Series for Adults ≥18 Years)

• Second dose: 1 month after the first dose 3
• This accelerated schedule provides earlier protection 3

Twinrix (Combination Hepatitis A/B)

• Standard schedule: 0,1, and 6 months 4
• Accelerated schedule: 0,7,21-30 days, and 12 months 3, 4

Common Pitfalls to Avoid

• Do not restart the series if the second dose is delayed—this wastes vaccine and delays protection 2, 3
• Do not give the second dose earlier than 4 weeks after the first dose (except within the 4-day grace period) 1, 2
• Do not use inadequate doses or shorter intervals, as these must be readministered 1, 3

High-Risk Populations Requiring Urgent Vaccination

The following groups should receive their second dose urgently if delayed: 2, 3, 4

• Healthcare personnel with potential blood/body fluid exposure 4
• Hemodialysis patients 2, 4
• Household or sexual contacts of HBsAg-positive persons 2, 3
• HIV-infected persons and other immunocompromised individuals 2, 4
• Persons born in countries with HBV endemicity ≥2% 3, 4
• Men who have sex with men 2
• Current or past persons who inject drugs 2