May 2, 2006
Will persons who recover from pandemic flu be immune (protected) from re-infection, and thus able to return to work even without vaccination or antiviral prophylaxis?
As truly terrible as the worst flu pandemic of the 20th century was, from 1918-1920, over 97% of infected persons survived, considering that the case-fatality rate (CFR) was ~2.5%.
Influenza is not a chronic infection, unlike other viruses such as HIV. If infection with one specific influenza virus, including the world’s next pandemic influenza virus, confers immune–protection in the vast majority of people who survive, then they may be able to return to work even during the pandemic when neither pandemic vaccine nor sufficient prophylactic antiviral drugs are available.
Given that influenza virus causes non-specific “influenza-like-illness (ILI)” of fever and cough, like many other viruses or bacteria, it would be important to have a rapid, reliable, and affordable diagnostic test to verify that a person has been infected with the future pandemic flu virus.
Development of such a diagnostic-immunity lab test should be a priority for the US government’s pandemic flu preparedness effort. R & D for such a lab test could be supported by a public-private partnership involving government (perhaps HHS, DHS, DARPA or others) and commercial companies with expertise in developing diagnostic tests.
Ideally, this pandemic flu diagnostic-immunity lab test would be both qualitative (proving that at least some form of an immune response developed to the specific pandemic flu virus) and quantitative (e.g., proving that an immune response thought to be protective to the flu virus has been made).
Reasoning by analogy to such immunity tests for current influenza viruses in persons who have been infected, or who have received an influenza vaccine, would provide a roadmap for adapting such assays to the future pandemic flu virus. For example, use of a 1:40 titre of neutralizing antibody was used as a quantitative threshold for protection against H5N1 in the US clade 1 prototype H5N1 vaccine study published in the March 30, 2006 New England Journal of Medicine).
Lastly, the Washington Post editorial April 21, 2006 appropriately called attention to the severe lack of hospital preparedness and the dire shortage of health care workers during the predictable surge in medical needs with the next flu pandemic. In a letter to the Post, published April 29th and written in response to this editorial, I raised the same issue of whether persons who recover from the next pandemic flu virus might be immune-protected from re-infection and thus may not require vaccination or antiviral prophylaxis. Such persons might provide significant mitigation of the certain shortage of health workers, and other critical societal infrastructure workers (e.g., Fire/EMS, police, truck drivers, IT persons, military, and many others).
Even so, given current pandemic preparedness efforts, health care workers will NOT will be able to “handle the pandemic” (in reference to a quote taken from the title of this April 29th letter that was independently added by the Washington Post). Pandemic flu modeling should explore the effect of health care and other workers reentering the work force after recovering from pandemic flu infection, both in their local communities and in more distant communities, in response to the contemporaneous, but not always simultaneous “wave” of pandemic flu as it spreads across the US and the world.
Daniel R. Lucey, MD, MPH
Director, Center for Biologic Counterterrorism and Emerging Diseases
EROne Institutes, Washington Hospital Center
Co-Director, Master of Science Program in
Biohazardous Threat Agents and Emerging Infectious Diseases
Georgetown University School of Medicine