wild-type a/victoria/75 virus challenge of 34 of the vaccinated volunteers and 12 others who had had prior natural a/victoria/75 virus infection revealed similar and significant protection when compared with the 96 % infection and 68 % febrile illness or systemic illness or both observed in 25 unvaccinated volunteers with little or no serum antibody .
C0042769
virus infection
C0009450
infection