Flu shots & heart attacks
According to a new British study yearly flu shots may protect against heart attacks, and the earlier in the season a shot is given the greater the protection. Niroshan Siriwardena, a professor of primary and pre-hospital health care at the University of Lincoln said, “The risk of getting a heart attack was reduced by 19 percent for those who had a vaccination in the past year.”
This study was based on a review of the medical records of more than 78,000 people in England and Wales. Around 16,000 of them were heart attack patients, and almost 8,500 of the heart attack patients had been vaccinated. The study was criticized by some experts in US. Dr. Kirk Garratt, associate director of the division of cardiac intervention at Lenox Hill Hospital in New York City pointed out that there were 19 percent fewer heart attack patients vaccinated in the previous year, not that there was a 19 percent reduction in heart attacks among the vaccinated. If getting a flu shot could prevent 19 percent of heart attacks, it would have been noticed before now, Garratt added.
Dr. Harlan Krumholz, director of the Yale-New Haven Hospital Center for Outcomes Research and Evaluation at Yale Medical School also pointed out this flaw in the study. He said it has been said before that there was a connection between flu shots and heart attack prevention but this data does not justify the link.
Siriwardena retaliated to this criticism saying, that the study looked at “the likelihood of heart attack in vaccinated and unvaccinated patients, adjusting for other risk factors for heart attack.” “We expressed our results as risk of heart attacks,” he added. But Garratt said that statement was incorrect. “This study did not measure risk of heart attack in vaccinated and non-vaccinated people. It measured rates of vaccination among heart attack patients and those without heart attack,” Garratt said. Siriwardena said, “I think it is important again to say again that we found an association rather than proving cause-and-effect. We also found a greater association between reduction of heart attack and early vaccination.”
In any event all doctors including those who are criticizing this study are recommending everyone to be vaccinated. Krumholz said, “The study is timely because we're trying to encourage people to get vaccinated…The findings reinforce the recent clear evidence that vaccinations are beneficial.” He added that the American Heart Association and the Association of American Cardiologists both recommend flu shots for people who have heart disease or have a high risk of developing cardiovascular problems.
Garratt explained that a flu infection can trigger a rupture of plaque inside arteries, causing a heart attack. Plaques are hardened fats and other substances that can build up on artery walls and cause blockages. Flu also raises inflammation levels in the body, possibly setting the stage for a heart attack, Krumholz added.
The study was published in the September issue of the Canadian Medical Association Journal.
Flu prevention guidelines
The US Centers for Disease Control and Prevention (CDC) has also issued new guidance for preventing flu in healthcare settings. This also includes surgical masks rather than N-95 respirators when providing routine care for flu patients. In the middle of June the CDC previewed the change to its personal protective equipment (PPE) recommendation when it asked the public to comment on the proposed guidance. Society for Healthcare Epidemiology of America (SHEA) approved the new mask recommendation and its focus on the latest scientific data.
Previous CDC pandemic flu prevention guidance for healthcare settings has recommended N-95 respirators for protecting workers who care for flu patients, but the advice has been controversial. Some health care workers had complained that the N-95s are uncomfortable to wear for long periods.
According to the CDC the newest version of the 17-page guidelines for seasonal flu has taken into account the wide availability of a trivalent seasonal flu vaccine that includes the 2009 H1N1 virus, which the CDC expects to see again during the upcoming flu season. The guidelines also estimate the hospitalizations and deaths from the 2009 H1N1 virus.
Australian researchers however have found that respirators may be better than masks at protecting healthcare workers, though the difference may not be significant. An October 2009 Canadian study of flu in nurses suggested that masks were not inferior to N-95 respirators. A study in January showed that surgical masks and hand hygiene reduced flulike illnesses in the college setting.
Dr John Jernigan, a medical epidemiologist with the CDC said that as the face of the 2009 H1N1 virus looks more and more like seasonal flu, changes in the new guidance emphasize droplet precautions in the context of a multifaceted flu prevention approach. “PPE is likely to be one of the least effective methods, with vaccination being most important,” he said.
Dr Jeff Hageman, an epidemiologist with the CDC said that the new guidelines showed a continuing need for more research. “There is a lack of data to definitively say which modes are more important,” he said. The guidelines also recommend measures to prevent flu transmission during periods of increased flu activity, such as segregating patients with suspected flu who present for care and minimizing visits from patients with mild flu like symptoms who are not at increased risk of complications.
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