Tuesday, July 2, 2013

Vaccines, Swine Flu and Paralysis

The H1N1 (swine flu) vaccine that was administered in 2009 received a lot of attention after a recent study linked it with a rare, paralyzing disease. People given the H1N1 vaccine had a small increased risk of developing Guillain-Barré Syndrome (GBS), a disorder that affects the peripheral nervous system. The disorder was originally linked to vaccines in 1976 with a vaccine created for a swine flu epidemic.  Doctors have stated that the benefits of the vaccine outweigh the risks.

GBS is a rare autoimmune response where a person’s own immune cells attack the protective coating on nerve fibers; specifically those that control movement and respiration. It’s characterized by symmetrical weakness, usually affecting the lower limbs first and then progressing to other parts of the body. It affects one person in every 100,000 and can lead to paralysis, but is usually temporary and 80% of patients have a full recovery.  Most GBS cases occur after a bacterial or viral infection and take a few days or weeks to develop.

The US Department of Health and Human Services conducted the study, with Dr. Daniel Salmon of the National Vaccine Program Office leading the research.  Twenty-three million people were vaccinated for H1N1 in 2009 and data was gathered from six different adverse monitoring systems.

Dr. Salmon’s group found that 77 people developed Guillain Barré syndrome within 91 days of receiving the vaccine. The vaccine accounted for an extra 1.6 people per million developing the condition. However, in 2009, the H1N1 “Swine Flu” pandemic infected 61 million people and caused 12,470 deaths. The vaccine is credited with preventing nearly a million cases of H1N1 and saving 500 lives.

“Clinicians, policy makers, and those eligible for vaccination must consider the overall risks and benefits of vaccination, as defined by epidemiological studies,” Dr. Salmon concludes. “But [people] should be assured that the benefits of influenza A (H1N1) 2009 monovalent inactivated vaccines greatly outweighed the risks.”

Another group of researchers spent 13 years compiling data on millions of patients and have found no link between vaccines and GBS. Researchers studied tetanus, hepatitis, pneumonia and flu vaccines and found no heightened risk for GBS.

Most studies done since 1976 have found no link between GBS and vaccines. Only a couple studies have shown a small increase in risk among people who received flu vaccines, including the 2009 shot against H1N1. Dr. Roger Baxter, the co-director of the Vaccine Study Center at Kaiser Permanente in California was the lead author on the study and noted that because GBS is so rare, its extremely difficult to determine whether a particular vaccine could have caused increased cases, which is why this study looked at millions of patients.

“There’s definitely a connection in people’s minds that vaccines cause this syndrome. But if you look at the (medical) literature, that doesn’t bear out,” Dr. Baxter states. “The bottom line is we think vaccines are very safe for this outcome, that they do not result in GBS, and if they do, it’s so rare it’s nothing to be worried about.”

The study notes that there were 415 cases of GBS from 1995 to 2006, and two-thirds of those had a documented gastrointestinal or respiratory infection in the weeks before developing GBS. Only 25 people had received a vaccine of any kind within six weeks of the onset of GBS. It was also noted that GBS cases were 50 percent more common in the winter, mirroring seasonal rates of infections like the flu and other respiratory illnesses.

Dr. Daniel Salmon of the Institute for Vaccine Safety at John Hopkins University said, “The take home message is vaccines are not causing Guillain-Barré Syndrome at a rate, if at all, that would possibly make the benefits of vaccination not worthwhile.”

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