Hepatitis A+B Combined

Travelers to endemic areas, people at risk for both hepatitis A and B.

Severe allergic reaction (anaphylaxis) to a previous dose of Twinrix, or to any hepatitis A or hepatitis B vaccine, or to any component including yeast and neomycin. Moderate to severe acute illness (defer until recovery).

Very common (≥1/10): injection site pain and redness (35–41%), headache (22%), fatigue (18%). Common (1–10%): injection site swelling, fever, malaise, nausea, diarrhea, myalgia. Serious adverse events are extremely rare. Safety profile is consistent with that of monovalent hepatitis A and hepatitis B vaccines individually.

Standard schedule: 3 doses IM at 0, 1, and 6 months (same as hepatitis B). Accelerated schedule: 4 doses at 0, 7, 21–30 days + booster at 12 months (for travelers with insufficient time for standard schedule). Dose: 1.0 mL intramuscular in deltoid. Pediatric formulation (Twinrix Junior): 0.5 mL, ages 1–15 years. Store at +2°C to +8°C, do not freeze.

Anti-HAV seroconversion: 93.8% after dose 1, 98.8% after dose 2, 99.9% after dose 3. Anti-HBs seroprotection (≥10 mIU/mL): 30.8% after dose 1, 78.2% after dose 2, 98.5% after dose 3. Accelerated schedule: 82% anti-HBs seroprotection at day 28 (after 3 doses), rising to 98.5% after booster at 12 months. Long-term protection: comparable to monovalent vaccines (HAV: ≥25 years, HBV: ≥30 years estimated).

Can be co-administered with most travel vaccines (yellow fever, typhoid, meningococcal, rabies) at different injection sites. Immunoglobulins (HAV IG or HBIG) may be given at a separate site if immediate post-exposure protection is needed, though anti-HAV titers may be slightly reduced. No known clinically significant drug interactions.

Safe in pregnancy when indicated (inactivated vaccine). Safe in breastfeeding. Immunocompromised patients may have reduced response — consider checking anti-HBs titers after completion. Not a substitute for post-exposure prophylaxis when immediate protection is needed (use monovalent + immunoglobulin). Persons already immune to one component can still safely receive the combination.