Study says to base flu policy on life-years saved
July - August, 2008 | Volume 7, Issue 4
Vaccine should be given in a flu pandemic to the age groups with the most potential years of life at risk, according to a team of Fogarty scientists writing in the August 1 issue of Journal of Infectious Diseases.
This conclusion stems from considerations about the age groups experiencing the highest mortality risk in past flu pandemics and considerations about vaccine efficacy and life expectancy, both of which decline with age.
In the article, "Prioritization of Influenza Pandemic Vaccination to Minimize Years of Life Lost," Dr. Mark Miller, director of the Division of International Epidemiology and Population Studies, and Fogarty scientists Dr. Cecile Viboud, Dr. Rebecca Grais and Maia Rabaa applied a "years of life lost" (YLL) metric--not just overall mortality--to U.S. mortality statistics collected during the influenza pandemics of 1918, 1957 and 1968.
In the event of another pandemic, vaccine is likely to be in short supply in the United States, they say, making allocation decisions critical.
The direct benefits of vaccination, and age patterns of mortality risk in pandemics, all shift attention away from seniors and toward either younger adults or children as the optimal target to mitigate mortality, the article says.
"The question of who should be vaccinated first needs to be debated and reasoned through now, before the onset of a public health emergency, while we have the time to reflect on which decision-making metric is the most appropriate," the authors conclude.
They said their study is not a policy prescription itself, but "highlights how the choice of health outcome metrics such as YLL can influence the prioritization of age groups to vaccinate in pandemic settings."
Calling theirs "a conservative metric that captures the major health burden of pandemic influenza with no need to set arbitrary values on quality of life," the authors say they are the first to quantify the benefits of vaccination by using years of life potentially saved in a future pandemic.
The ethical question raised in setting priorities is whether one life has more or less value than another.
"We do not make judgments about the values of people's lives, but it is important to debate such ethical and medical considerations now, and to propose rational vaccine strategies based on science, rather than making hasty decisions in the middle of an on-going pandemic crisis," said Viboud.
Data indicate that in a 1918-like scenario, the most years of life that could be saved by targeted vaccination would be among those under age 45; in a 1968-like scenario, those between 45 and 64; and in a 1957 scenario, people over 45.
The government's pandemic preparedness draft plan, revised in July, places priority on key government officials, health care workers and emergency responders, followed by children in severe and moderate flu scenarios, while seniors are given priority over children in a mild scenario.
Prioritization of Influenza Pandemic Vaccination to Minimize Years of Life Lost. Mark A. Miller, Cecile Viboud, Donald R. Olson, Rebecca F. Grais, Maia A. Rabaa and Lone Simonsen. Journal of Infectious Disease, 2008; 198:305-311.
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