Pandemic Spread and Antigenic Shift

Using Previous Years of Progress to Understand the Pandemic Virus

Dr. Keith E. Jensen, head of the CDC Respiratory Disease Unit and WHO International Influenza Collaborating Center, noted that “the phenomenon of antigenic variation among the viruses which cause influenza has been recognized since the earliest vaccine trials as a basic problem in the development of effective control of the disease by immunization.” That is to say that scientists who have studied influenza had noted that the influenza viruses ability to change had been a constant problem in creating influenza vaccines that matched circulating influenza viruses since the earliest vaccine trials in the 1940s.

The 1957 pandemic influenza virus – influenza A(H2N2)- was the first occurrence of antigenic shift – an abrupt, major change in an influenza A – in influenza viruses that could be observed in a laboratory setting. Using influenza viruses collected from earlier influenza surveillance scientists were able to compare earlier strain of influenza A viruses with influenza viruses collected from outbreaks that occurred in 1957 all over the world – something that would have not been possible without the previous years of developing a global system of influenza surveillance.

When comparing influenza virus isolates with isolates from influenza outbreaks in Asia, Europe, and the U.S. in early 1957, scientists noted that influenzas viruses isolated in 1957 were very different from viruses isolated in pervious years. With this knowledge, public health authorities were able to develop accurate diagnostic tests and provide more information for the eventual creation of an influenza vaccine to combat the 1957 pandemic influenza virus.