"As in 1957, a new influenza pandemic arose in Southeast Asia and acquired the sobriquet Hong Kong influenza on the basis of the site of its emergence to western attention. Once again, the daily press sounded the alarm with a brief report of a large Hong Kong epidemic in the Times of London. A decade after the 1957 pandemic, epidemiologic communication with mainland China was even less efficient than it had been earlier. As this epidemic progressed, initially throughout Asia, important differences in the pattern of illness and death were noted. In Japan, epidemics were small, scattered, and desultory until the end of 1968. Most striking was the high illness and death rates in the United States following introduction of the virus on the West Coast. This experience stood in contrast with the experience in western Europe, including the United Kingdom, in which increased illness occurred in the absence of increased death rates in 1968–1969 and increased death rates were not seen until the following year of the pandemic. Since the Hong Kong virus differed from its antecedent Asian virus by its HA antigen, but had retained the same (N2) NA antigen (16), researchers speculated that its more sporadic and variable impact in different regions of the world were mediated by differences in prior N2 immunity (16–19). Therefore, the 1968 pandemic has been aptly characterized as "smoldering". Further evidence for the capacity of previous N2 experience to moderate the challenge of the Hong Kong virus was provided by Eickhoff and Meiklejohn, who showed that vaccination of Air Force cadets with an H2N2 adjuvant vaccine reduced subsequent influenza from verified H3N2 virus infection by 54%."