Immune memory assessment three years following a single dose of hepatitis a vaccine at 12, 13 or 19 months of age.

INTRODUCTION

We aimed to evaluate immunological memory after three different single-dose hepatitis A vaccination schedules.

METHODS

Children were vaccinated using one of three schedules: 1) Twinrix®Junior at 12 months (Twinrix12); 2) Vaqta®pediatric at 13 months (Vaqta13); or 3) Vaqta®pediatric at 19 months of age (Vaqta19), followed by a challenge dose with Twinrix®Junior three years later. Blood samples were collected before and one month post-challenge dose.

RESULTS

A total of 320 children were included in this analysis. Seropositivity (≥20 mIU/mL) three years post-primary vaccination was lower for the Twinrix12 schedule (40.2 %) compared to the Vaqta13 (65.6 %) or Vaqta19 schedules (77.6 %). One month post-challenge dose, the proportion of participants with an anamnestic response was high and similar across the three schedules (Twinrix12: 97.5 %; Vaqta13: 98.4 %; Vaqta19: 96.1 %).

CONCLUSION

Single-dose hepatitis A vaccination induced a strong immune response across the three schedules. However, further studies are needed to confirm long-term durability and population impact.