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Biosecurity News in Brief
First Wave of Pandemic May Protect Against Later WavesBy Amesh Adalja, September 29, 2008 The November 15, 2008, issue of the Journal of Infectious Diseases includes a study about the 1918-1919 influenza pandemic and cross-protective immunity that may have resulted from an early wave of the virus.1 The 1918 influenza pandemic is thought to have occurred in 3 waves, commencing with a mild first wave in the spring or summer of 1918 followed by the extremely lethal 2nd wave. The first wave was known to have spread through U.S. Army training camps. This study analyzes morbidity and mortality data from these camps to determine whether troops gained some cross-protective immunity from the second wave when exposed to the first wave of the pandemic virus.1 The authors, who include The Great Influenza author John M. Barry, collected medical records from 37 U.S. Army camps, the British Grand Fleet, and 12 British civilian communities from the time of the pandemic. Of the 37 U.S. Army camps, 5 camps had detailed data on influenza-like illnesses and length of tenure in the Army—a surrogate for exposure to the first wave. Analysis of the data revealed that troops who were exposed in the first pandemic wave were afforded 86% protection from influenza illness in the second wave. Somewhat similar protection rates were found with members of the British Grand Fleet and the British civilian population.1 According to the authors, these results indicate that successive waves of infection in the 1918 pandemic were likely caused by sequential genetic variants of the A/H1N1 virus, with the first variant not being adapted enough to human hosts to cause widespread disease but still able to induce cross-protective immunity. Recognizing the limited nature of their data, the authors suggest only that public health interventions for future pandemics should consider the possibility of some degree of cross-protection among waves of infection, which may impact intervention strategies.1 References
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