H7N3 live attenuated influenza vaccine has a potential to protect against new H7N9 avian influenza virus.

After recent emergence of new avian influenza A(H7N9) viruses in humans many people and Governments are asking about H7 influenza vaccine which could provide cross-protection against new viruses, until H7N9 vaccine is prepared from a relevant strain. Here we scientifically justify that available H7N3 live attenuated influenza vaccine (LAIV) can be protective against H7N9 viruses due to the presence of conserved immune epitopes in its hemagglutinin. We used Immune Epitope Database analysis resource to predict B-cell and CTL epitopes distributed across H7N3 HA molecule and assessed their identity with new H7N9 viruses at near 70% and 60% of the epitopes, respectively. In addition, we tested serum samples of volunteers participated in phase I clinical trial of H7N3 LAIV for the presence of anti-H7N9 hemagglutination-inhibition and neutralizing antibodies and found seroconversions in 44.8% of vaccinated persons, which suggests the potential of H7N3 LAIV to protect against new H7N9 avian influenza viruses.