Comparison of the Immunogenicity, Safety and Reactogenicity of FluBlok, To a Licensed Vaccine In Elderly Adults

Annual influenza epidemics are associated with serious excess morbidity and mortality, particularly among the elderly. Licensed trivalent inactivated influenza vaccines (TIVs) have been shown to reduce hospitalization and death following influenza in this vulnerable population, but their efficacy is lower than that observed in younger, healthy populations. In addition, recent studies have questioned the level of effectiveness of TIV in the elderly, suggesting that cohort studies have overestimated the benefits of immunization with current TIV formulations in this age group. In view of these considerations, it is widely accepted that improved and alternative vaccines are needed for control of seasonal and pandemic influenza. Currently available TIVs are prepared from viruses that are grown in embryonated hens' eggs. Alternative substrates for vaccine production are desirable in order to reduce the vulnerability of and to expand influenza vaccine supply. Recombinant DNA techniques allow for expression of the influenza hemagglutinin (rHA) by baculovirus vectors in insect cell cultures. Advantages of this technique include speed of production, absence of egg protein, and a highly purified product. Previous studies among healthy younger and older adults have confirmed that rHA vaccines are safe, well tolerated and immunogenic at dosages up to nine times higher than those contained in TIV. Dose-related increases in serum antibody levels after immunization also were observed.