Meantime, new research by US government scientists confirms what Canadian (and some other) researchers have been saying for years: flu shots can actually increase your risk of developing influenza. In a piece titled Swine study suggests flu vaccination may sometimes backfire, researchers found that vaccinating pigs for flu could also give them a more severe disease:
During the 2009 H1N1 pandemic, Canadian researchers identified a greater risk of infection in those who had been vaccinated against seasonal flu, a puzzling finding that researchers are still unraveling, including a group yesterday that revealed more about a mechanism for the process through experiments on pigs.
The heightened risk identified during the 2009 pandemic threatened to disrupt vaccination efforts in Canada, and the findings raised tough issues for policymakers, especially when studies in the United States and other countries contradicted the Canadian findings. However, in 2010 a large study by a Canadian team put an exclamation point on the earlier findings, reporting that the risk of needing treatment for pandemic flu was 1.4 to 2.4 times greater in those who had been vaccinated against seasonal flu in the previous year...
The researchers vaccinated piglets that were younger than 6 months old and hadn't been exposed to flu before against H1N2 to explore whether vaccine-induced antibodies might play a role in exacerbating respiratory symptoms. They found some of the piglets got sick with severe pneumonia and had severe lung damage after they were infected with the 2009 H1N1 virus, suggesting that cross-reactive antibodies triggered by the flu vaccine made symptoms worse after infection with a different flu strain...
In an editorial on the new findings, published in the same issue, James Crowe Jr, MD, wrote that the new findings show why health leaders should consider the principle "First, do no harm" when pursuing new ways to battle flu epidemics and pandemics. Crowe is a microbiologist and professor of pediatrics at Vanderbilt University and is director of the Vanderbilt Vaccine Center.
He noted that achieving a flu vaccine that would provoke lasting protection across a range of virus subtypes would be a major medical achievement, but eagerness to move forward with next-generation flu vaccines should be tempered with a focus on safety and minimizing risk.
The need to understand the molecular forces that direct antibody-enhanced virus replication or altered immune response isn't limited to vaccine effects, given that antibody-enhanced disease can occur in nature, Crowe wrote. He added that studies during the 2009 H1N1 pandemic suggested that cross-reactive antibodies may have played a role in severe disease seen in otherwise healthy young adults...Here is the link to the original paper.