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Public Health Officials Find Flu Nothing to Sneeze At
Smallpox, botulism, anthrax--the mere mention of these threats is enough to cause a heated debate in which science and politics hold equal sway. But the flu? Except for the yearly admonitions to get a flu shot, this virus gets relatively little attention.This is true despite influenza being responsible for thousands of deaths every year during epidemics and, in the past, wreaking havoc in major pandemics. In the past century, these pandemics killed tens of millions of people. The most widely known was the Spanish flu of 1918, which caused illness among 20 to 40 percent of the world's population, killing a total of 20 to 40 million people. In an eight-month period during the pandemic, 500,000 Americans died.
Each year in the U.S. alone, 114,000 people are hospitalized with the illness and 20,000 die, though these numbers may understate the true morbidity and mortality. These health effects account for $1 billion to $3 billion in direct medical costs.
Shifts and Drifts and Vaccine Development
Often confused with the common cold, the flu is caused by the influenza A, B, and milder C viruses, which have developed sophisticated mechanisms to change their structure over time, evading the immune system and complicating vaccine development. When changes are minor, which is a common annual occurrence, this "antigenic drift" allows for the appearance of several strains in the population.
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The National Immunization Program at the CDC predicts that in the advent of a flu pandemic, "social disruption, interruption of commerce, school closings, and public unrest are likely." --Erica Seiguer |
When the virus significantly alters its structure--so-called "antigenic shift"--a pandemic is possible. This process results in an entirely new virus to which few people, if any, will have immunity, allowing for rapid spread through communities. This is what happened in 1918; in the 1957 Asian flu, which claimed the lives of 69,800 Americans; and in the 1968 Hong Kong flu. In 1997, the isolation of novel strains in Hong Kong was thought to be a harbinger of the next pandemic and resulted in the slaughter of millions of chickens thought to be infected with the virus. Officials were especially concerned because the virus was transmitted directly from chickens to humans instead of passing through the usual intermediate host, the pig, and from person to person. It is thought that increased travel since these major pandemics will aid the virus in reaching all corners of the globe in an efficient--and deadly--manner.
The flu presents major challenges to scientists in the public and private sectors, as well as to policymakers. Beyond the development and delivery of yearly flu vaccines to millions worldwide, preparation for what some believe to be the next, inevitable flu pandemic is a constant concern. Understanding the process by which the yearly flu vaccine is developed sheds light on the complexities of adequately addressing the threat.
International Cooperation
The international influenza surveillance system that the WHO coordinates is a network of individuals, laboratories, and organizations that are constantly monitoring circulating strains. The Centers for Disease Control and Prevention (CDC) in Atlanta receives strains collected from the U.S. and abroad and analyzes which are most likely to appear in the next flu season. The CDC, WHO, and the Food and Drug Administration work from January to March each year to come to agreement on the three strains to be included in the vaccine for the upcoming season.Concurrent to these analyses and decisions, the four vaccine manufacturers licensed in the U.S. have to plan and begin production as soon as the vaccine strains are agreed upon and announced by the FDA. The vaccine is grown in eggs, so during the early months of the year, vaccine manufacturers purchase these eggs in anticipation of the information to be released by the FDA. Between this time and September of each year, manufacturers work closely with the FDA to ensure the production of nearly 100 million doses of safe and effective vaccine.
This schedule is very tight, and delays at any stage can result in vaccine hitting the shelves too late to protect vulnerable people from the late-fall and early-winter flu season. The 2000-2001 flu vaccine shortage highlighted a worrisome failure to coordinate immunizing high-risk individuals first. According to an audit by the General Accounting Office, there was no formal mechanism in place to ration the available vaccine to those most in need.
These challenges arise each year and would most likely be dwarfed in the event of a pandemic by the huge mobilization of resources required--and not necessarily assured--to produce enough vaccine for global consumption and launch a mass campaign of public vaccination. History provides us with some lessons in this matter.
In 1976, after much debate, the U.S. government launched a mass influenza vaccination campaign after the discovery of an isolated flu strain thought to be related to the dreaded Spanish flu. The vaccination of 40 million Americans marked a triumph for the public health infrastructure's ability to mobilize quickly and efficiently. Yet the episode is widely remembered as a debacle because the killer bug never spread farther than the military base where it was isolated, and Guillain-Barré syndrome was diagnosed in about 1,000 vaccinated individuals. The campaign ended less than three months after it was launched.
In the aftermath of the perceived failure, an independent investigation was launched at the request of the then-director of the Department of Health, Education and Welfare, Joseph Califano. The report, The Epidemic That Never Was: Policy Making in the Swine Flu Scare, co-authored by Harvey Fineberg (former dean of HSPH and provost of Harvard University) and Richard Neustadt of the Kennedy School, chronicled the evidence and decisions that led to the recommendation by President Ford to commence mass vaccination. The litigation following the vaccination campaign--in which those who had been immunized sought damages for alleged sequelae--has clouded all research and planning since then.
Preparing for the Next Pandemic
In addition to the technical challenges of isolating and developing the flu vaccine each year, there is a host of other obstacles to confront. First and foremost is the supply of vaccine. Each year, about 230 million doses are produced around the world while in a pandemic, hundreds of millions more would be needed, possibly under tighter time constraints.Equally important would be political leadership charged with making tough decisions about mass vaccination while bearing in mind the results of past efforts. The current deliberation over the smallpox vaccination strategy in the U.S. provides an interesting counterpoint to concerns about a flu pandemic. Public and private debate over the former has taken well over a year--much more time than would be available in the case of a virulent flu. The National Immunization Program at the CDC predicts that in the advent of a flu pandemic, "social disruption, interruption of commerce, school closings, and public unrest are likely," and the direct costs of such a plague could range from $71 billion to $166 billion in the U.S. alone.
--Erica Seiguer, a fourth-year MD-PhD student at HMS
Websites of Interest
CDC National Vaccine Program Office (NVPO) Pandemic Influenza WebsiteWorld Health Organization Influenza Website
FluNet, The Global Influenza Surveillance Network
CDC National Immunization Program Flu Fact Sheet
The opinions expressed in this column are not necessarily those of Harvard Medical School, its affiliated institutions, or Harvard University.