CDC balks at linking SARS and flu shots

Public misconceptions may undermine effort

Diverging from the position taken by the Geneva-based World Health Organization (WHO), the Centers for Disease Control and Prevention (CDC) will not urge influenza vaccination for the 2003-2004 season specifically as a response to the possible return of severe acute respiratory syndrome (SARS), Hospital Infection Control has learned.

"We are quite concerned that people will somehow begin linking up SARS and influenza vaccine in their minds, and that will to lead to confusion," says Keiji Fukuda, MD, a leading influenza expert at the CDC. "[People may say], I heard you need to get vaccinated so you won’t get SARS,’ or I heard that SARS may result from flu vaccine,’ and so on. These [misconceptions] have big programmatic implications. The more people get confused about a vaccine, the more it really harms overall vaccination efforts."

Indeed, the annual flu immunization effort probably still feels the lingering effects of the ill-fated swine flu campaign of 1976. In one of the more memorable public health debacles in U.S. history, the government tried to vaccinate every citizen against a novel swine flu strain that appeared bound for widespread emergence. Though some cautioned prudence, fear that the legendary 1918 Spanish flu swine strain had reappeared resulted in a massive vaccine production and immunization effort. The cure proved worse then the disease, as the novel strain never emerged and some vaccinees developed a rare form of disease and paralysis called Guillain-Barre syndrome.

The incident still is studied in public health schools as a cautionary tale of a flu vaccination campaign that took on a disastrous life of its own.1

Nevertheless, the WHO made the decision to distinctly link flu vaccine this season with SARS, arguing that increasing the number of vaccinated people will eliminate some febrile illness that may be mistaken for SARS.

"The recent global outbreak of SARS has heightened concern about the occurrence of respiratory diseases having symptoms similar to those seen in SARS," the WHO said in a Sept. 2, 2003, statement.

As the recurrence of SARS during the influenza season cannot be ruled out, some health authorities are concerned that cases of influenza and other respiratory diseases, particularly when they occur as clusters in health care facilities, could raise suspicions of SARS, resulting in disruption of health services as well as costly precautionary measures and investigations, the organization stated.

"WHO continues to recommend that priority for influenza vaccination be given to those groups at highest risk of developing serious complications from influenza and to those health workers caring for them," it noted. Such targeted use of influenza vaccine provides "the most effective strategy" for reducing the health burden of influenza reducing cases of respiratory disease that could be mistaken for SARS, the WHO concluded.

"In the WHO message, it came out that if you do this [flu shots], it will clearly have benefits in terms of workups for SARS." Fukuda says. "I think it is a little bit simplistic in how they presented that. What we will end up emphasizing is that influenza vaccinations are primarily done for influenza — and make that very clear. It’s possible that influenza vaccination in some places under some conditions could reduce the number of febrile cases, and that would reduce the number of people being evaluated for SARS. But this is definitely not the main reason to get vaccinated."

What about message to health care workers?

The WHO also cited the transmission of SARS within health care settings involving a large number of health care workers as "a striking feature of the global outbreak." Symptoms of fever and lower respiratory tract infection (cough, difficulty breathing, shortness of breath) in two or more health care workers in the same health care unit, with onset of illness in the same 10-day period are regarded by the WHO as cause to suspect a possible outbreak of SARS and reason to conduct further radiographic and laboratory investigation. Thus, immunizing health care workers could avert such investigations, but the CDC is wary of advocating that strategy as well.

"We will really strongly push for [health care workers] to get immunized for the same essential reasons as in the past — they can be an important conduit for getting patients infected," Fukuda says. "So this is really a quite good way to protect patients. In some instances, it could also help to reduce nosocomial outbreaks. But it is not something that we want to push as a major strategy to build a SARS prevention program around. These nuances are a little bit complicated so trying to get this out reasonably simply so people understand on the first take is difficult."

The CDC position is consistent with past influenza campaigns in which the agency resisted linkage with flu shots and, for example, the anthrax attacks that caused initial flulike symptoms in those exposed, says William Schaffner, MD, chairman of the department of preventive medicine at Vanderbilt University Medical Center in Nashville, TN.

"They have always been nervous about using that rationale," he says. "They were not keen on it in the post-anthrax period for the same reasons. They think it is kind of a false reason. They are afraid that people who get vaccinated against flu may get the notion that they are protected against SARS because people don’t pay that much attention to the message. They think that that kind of external, fear-based logic isn’t sustaining. It may get some people vaccinated this year, but it won’t help in the long run."

Still, Schaffner says there is logic in strongly urging flu vaccination because of a possible return of SARS.

"Anything that will encourage people to get vaccinated is a good thing," he says. "I think it would be a good idea to have as much protection as possible so that if there is more SARS, we have less influenza to deal with simultaneously. We’re left with the educational piece, of course, which is that influenza means influenza. It does not mean any of the other respiratory viruses."

Linking SARS to health care worker vaccinations makes less sense, but the abysmal record on that front is still kind of shocking in an era of patient safety.

"The issue of health care workers and annual influenza vaccination leaves me grumpy," says Schaffner. "I find it personally inconceivable that health care workers would not want to get vaccinated. Health care institutions are doing a reasonable job in providing the vaccine, but such a minority of health care workers avail themselves. I would think that we ought to be close to 100% [immunized]. We have not sufficiently given them the other half of the message: We are asking you to get a flu shot so you don’t give flu to your patients.’"


1. Brown D. A shot in the dark: Swine flu’s vaccine lessons. The Washington Post, May 27, 2002: A/9.