A Phase I Clinical Trial for Inactivated Quadrivalent Influenza Vaccine (Split Virion) in Healthy Adults in China

Influenza is an acute respiratory disease caused by influenza viruses. There are three types of the virus including A, B and C. Both type A and type B viruses can cause acute febrile respiratory tract infection, characterized by sudden fever, headache, muscle pain, cough, sore throat, nasal congestion and general malaise. Influenza can periodically cause worldwide pandemic. For nearly a century, the influenza virus had occurred four large variation, causing three world pandemic. Studies have shown that since 1957, most of those new variants of influenza virus started in China, which is recognized by the world to have high incidence of influenza. At present, trivalent influenza vaccines are widely used in China. They only contain two kinds of type A virus antigens and one type B virus antigen. But since 2000, two kinds of type B strains (Victoria and Yamagata) have caused an alternating cycle in different seasons. Gradually, evolved from the original single lineage of influenza B virus B/Yamagata, two distinct antigenic lineages-B/Victoria and B/Yamagata have alternately dominated or caused a mix of popular lineage. These two lineages have little or nearly no cross-protection. Therefore, trivalent influenza vaccines may not cover the popular strains of influenza B virus, whereas quadrivalent influenza vaccines will help to simultaneously prevent two kinds of type A viruses and two kinds of type B virus.