Vaxart’s oral vaccination route has potential to overcome the main obstacle to vector-based vaccination: anti-vector immune response. Many people have been naturally exposed to adenovirus and have antibodies that will react against the vaccine vector; this limits the effectiveness of vaccination against the target antigen. Anti-vector immunity also complicates the reuse (boosting) of a vaccine, and the ability to vaccinate for multiple antigens using a single vector. Published studies and Vaxart's preliminary data suggest that serum anti-vector neutralizing responses are not mirrored in the intestinal environment, allowing oral delivery to circumvent pre-existing immunity. Further, long-term intestinal neutralizing responses are difficult to achieve by any method, suggesting that any anti-vector immunity imparted through oral delivery will wane and allow for additional vaccinations to be performed using the same vector without a reduction in efficacy.