Although the Russian flu vaccine used during the program is expected to provide some protection against Brazilian flu, the level of protection provided is uncertain. According to CDC, flu immunizations should be completed by late November for optimal program effectiveness. The 1978-79 flu program was originally planned to meet this schedule. However, by the end of November, fewer than 600,000 doses had been administered.
When antigenic and molecular characterization of this virus showed that both the HA and NA antigens were remarkably similar to those of the 1950s, this finding had profound implications. Where had the virus been that it was relatively unchanged after 20 years? If serially (and cryptically) transmitted in humans, antigenic drift should have led to many changes after two decades. Reactivation of a long dormant infection was a possibility, but the idea conflicted with