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This award-winning blog supplements the articles in Hospital Infection Control & Prevention.

Study: Mandated Flu Shots for Healthcare Workers 'Unsupported by Science'

By Gary Evans, Medical Writer

In a controversial finding that could bolster legal challenges to mandatory flu vaccination of healthcare workers, researchers report that the four randomized clinical trials (RCTs) commonly cited to justify compulsory immunization lack scientific rigor and overstate the protective benefit to patients.

After an elaborate deconstruction using the “dilution” principal of mathematics, the authors conclude there is insufficient scientific evidence to mandate flu vaccine as a condition of healthcare employment.

“It is unsupported by science -- that is clearly the answer,” says the lead author of the study, Gaston De Serres, MD, of the Institut national de santé publique du Québec, Quebec City, Canada. “When you are mandating a public health intervention you better be sure that the burden of disease that you want to prevent is substantial. At this time no one knows how many patients are infected annually in the United States by unvaccinated healthcare workers. Nobody knows.”

De Serres emphasized that voluntary influenza vaccination should still be encouraged and the findings should not in any way be construed as supportive of the broader anti-vaccine movement.

“I personally receive the [flu] vaccine every year,” he says. “I’ve published hundreds of papers on vaccines and I am a strong advocate of vaccines. But it’s one thing to recommend to healthcare workers that the risk of you transmitting influenza to your patients may be very small but we recommend that you take the vaccine. That’s one thing, but it is quite another to say if you don’t get the vaccine you’re fired. It’s completely different.”

Having long acknowledged the flu vaccine is imperfect and subject to seasonal fluctuations in efficacy, William Schaffner, MD, a professor of preventive medicine at Vanderbilt University in Nashville, nevertheless favors mandatory immunization of healthcare workers despite the Canadian study.

“They only looked at the RCTs. These provide the most rigorous data, but we recognize that RCTs on this question are hugely difficult to do,” he says. “If we are going to address the entire question of the scientific, professional and ethical basis of mandates you ought to look at the entire body of evidence. There are any number of observational studies of one kind or another that could be added. Obviously they have profound scientific limitations also, but at least in my mind they add to the body of evidence that makes mandatory influenza immunization more than reasonable.”

Questioning the historical prevented-mortality estimates, De Serres and colleagues note that it may take between 6,000 to 32,000 healthcare worker immunizations to prevent one patient death from influenza.

“I have no argument with that, but that is not the only issue to consider,” Schaffner says. “We also don’t want to make patients ill with influenza, and that issue is not addressed. They put much of their emphasis on the most severe endpoint. Similarly, they didn’t look at any other potential benefits of immunization such as worker absenteeism during an influenza outbreak, or the extended [protective] benefit to the worker’s family. These may not be the primary issues underlying a mandate, but they sure have come up in virtually every discussion of influenza vaccination mandates that I have read or written about."

Schaffner concludes by raising the central question: How much evidence is necessary in order to make a recommendation for a mandate?

“From my point of view, the accumulated evidence, including and beyond the RCTs is sufficient on a scientific, professional and ethical basis,” he says. “There must be 20 professional societies now that have agreed with this [mandate] position. If you take the RCTs all by themselves – off to the side – our Canadian colleagues have a point, but I don’t believe their point carries the day.”

For more on this story see the March 2017 issue of Hospital Infection Control & Prevention.

Gary Evans has written about infectious diseases, occupational health, medical ethics and a variety of other healthcare issues for more than 25 years. His writing has been honored with five awards for interpretative and analytical reporting by the National Press Club in Washington, DC.