How many doses of hepatitis A and hepatitis B vaccines should an adult receive?

Hepatitis Vaccine Dosing for Adults

For hepatitis B, adults should receive either 2 doses (Heplisav-B at 0 and 1 month) or 3 doses (Engerix-B, Recombivax HB, or PreHevbrio at 0,1, and 6 months), while hepatitis A requires 2 doses administered 6-12 months apart. 1, 2

Hepatitis B Vaccination

Standard Adult Dosing Options

Most adults aged ≥18 years have multiple vaccine options with different schedules:

• Heplisav-B (preferred for convenience): 2 doses at 0 and 1 month, achieving approximately 90% seroprotection 1, 2
• Engerix-B: 3 doses at 0,1, and 6 months 1
• Recombivax HB: 3 doses at 0,1, and 6 months 1
• PreHevbrio: 3 doses at 0,1, and 6 months 1

The 2022 ACIP guidelines now recommend universal hepatitis B vaccination for all adults aged 19-59 years, eliminating the need for risk factor screening. 1

Special Populations Requiring Modified Dosing

Hemodialysis patients and immunocompromised adults require higher doses:

• Recombivax HB: 40 μg (1.0 mL) per dose in a 3-dose schedule at 0,1, and 6 months 1, 2
• Engerix-B: 40 μg (2.0 mL) per dose in a 4-dose schedule at 0,1,2, and 6 months 1
• Annual anti-HBs testing is recommended with booster doses when levels fall below 10 mIU/mL 2

Important caveat: Heplisav-B and PreHevbrio have not been established as safe or effective in hemodialysis patients or pregnant women. 1

Pregnant women should only receive Engerix-B, Recombivax HB, or Twinrix due to insufficient safety data for Heplisav-B and PreHevbrio in pregnancy. 1

Hepatitis A Vaccination

Standard Adult Dosing

Adults require 2 doses of hepatitis A vaccine:

• Havrix: 2 doses at 0 and 6-12 months 1
• Vaqta: 2 doses at 0 and 6-18 months 1

After the primary series, antibody persistence extends beyond 10 years, with estimated duration of 21-27 years depending on the vaccination schedule. 3

Combined Hepatitis A and B Vaccine (Twinrix)

Twinrix provides protection against both hepatitis A and B and should be reserved for patients who need both vaccines:

Standard Schedule

• 3 doses at 0,1, and 6 months 1, 2

Accelerated Schedule (for rapid protection)

• 4 doses at days 0,7,21-30, followed by a booster at 12 months 1, 2

The accelerated schedule is particularly useful for travelers departing to endemic regions within 1 month. 4 At month 2 of the standard schedule, more than 99% of vaccinees are seropositive for anti-HAV and 84% are protected against hepatitis B. 5

Critical Timing Intervals and Interrupted Schedules

Minimum Intervals That Must Be Respected

For 3-dose hepatitis B series:

• Minimum interval between doses 1 and 2: 4 weeks 1, 2
• Minimum interval between doses 2 and 3: 8 weeks 1, 2
• Minimum interval between doses 1 and 3: 16 weeks 1, 2

If the schedule is interrupted, never restart the series—simply continue where you left off. 1, 2 This is a common pitfall that wastes doses and delays protection. If interrupted after the first dose, administer the second dose as soon as possible, ensuring the second and third doses are separated by at least 8 weeks. 1

Doses administered ≤4 days before the minimum interval are considered valid. 1

Special Consideration for Twinrix Accelerated Schedule

The 4-day grace period does not apply to the first 3 doses of Twinrix when using the accelerated schedule (days 0,7,21-30). 1 If the day 21-30 window is missed, administer the third dose as soon as possible—the series does not need to be restarted. 6 The fourth dose at 12 months remains essential and should be given 12 months after the first dose. 6

Expected Immune Response

Understanding the timeline of protection helps guide clinical decisions:

• After dose 1 of hepatitis B vaccine: 30-55% achieve protective antibody levels 2
• After dose 2: 75% achieve protection 2
• After dose 3: >90% of healthy adults aged <40 years achieve protection 2

Response rates decline with age: Only about 75% of persons aged ≥60 years develop protective antibody levels after a complete series. 2 This is an important consideration when vaccinating older adults, who may require revaccination or higher doses.

Common Pitfalls to Avoid

• Never restart an interrupted series—this wastes doses and delays protection 1, 2
• Do not give the third dose before 16 weeks from the first dose, even if 8 weeks have passed since the second dose 1, 2
• Do not use standard adult doses in hemodialysis patients—they require 40 μg doses 1, 2
• Do not use Heplisav-B or PreHevbrio in pregnant women or hemodialysis patients due to insufficient safety data 1
• Do not use Twinrix simply for hepatitis B vaccination when the patient has no indication for hepatitis A protection—this exposes patients to unnecessary hepatitis A antigen 2
• Lack of serologic testing should not be a barrier to vaccination—testing is not required before vaccination 1