Influenza viruses are associated with significant human disease and cause annual epidemics during autumn and winter. Although most people recover within 1 to 2 weeks without requiring medical attention, seasonal influenza yearly results in approximately 3 to 5 million cases of severe illness and up to 500,000 deaths worldwide, particularly among the very young, elderly, and chronically ill.~The H1N1 virus used for the challenge virus originated from a cell-culture derived candidate vaccine virus (ccCVV), provided by the Centers for Disease Control an Prevention (CDC) in the USA.~In Part A, 40 participants will be randomly allocated to one of two groups to be given one of two virus doses (Virus Dose 1 or Virus Dose 2).~Based on the outcome of Part A, participants in Part B, may be given Virus Dose 1, Virus Dose 2, or another virus dose (e.g., Virus Dose 3)
A total of up to 90 participants may be given H1N1 influenza challenge virus.~In Part A, 40 participants will be randomly allocated to one of two groups to be given one of two virus doses (Virus Dose 1 or Virus Dose 2).~Based on the outcome of Part A, participants in Part B, may be given Virus Dose 1, Virus Dose 2, or another virus dose (e.g., Virus Dose 3)