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Safety of 2009 influenza A H1N1 vaccine affirmed
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Of 99 serious adverse events reported after administration of the 2009 influenza A/H1N1 vaccine, 62 were likely unrelated to the vaccine, according to study results published online.
Barbara Pahud, MD, MPH, of Children’s Mercy Hospitals and Clinics in Kansas City, Mo., and colleagues reported data on 99 adverse events among the 3,928 H1N1 vaccine-related events in children reported to the Vaccine Adverse Events Reporting System (VAERS). Two hundred fourteen of the adverse events were categorized as serious, and of those, 109 were referred on to the CDC’s Clinical Immunization Safety Assessment network. The researchers said they had enough evidence as of January 2010 to report on 99 serious adverse events.
Forty-seven of the 99 events were described as neurologic, but most of these were deemed by the CDC researchers as not likely related to the vaccine; 15 events were described as allergic, 10 were described as respiratory in nature and 27 related to various other organ systems. The researchers classified the adverse events and vaccines as: eight definite, eight probable, 21 possible, 43 unlikely, 17 unrelated and two unclassifiable.
“It is reassuring to know that after immunizing over 7 million children with the monovalent 2009 H1N1 vaccine, only a couple hundred cases of serious adverse events were reported to VAERS,” Pahud told Infectious Diseases in Children. “We performed an in-depth clinical investigation of almost half of all reported serious adverse events and demonstrate that the majority were not causally related to vaccination. Most were attributable to other more likely causes, and those that were related to vaccination were mostly local reactions, anxiety reactions, syncope and allergic events. This is reassuring and relevant information since the H1N1 strain is included in this year’s seasonal influenza vaccine.”
Pahud and colleagues said their findings echo similar studies that support the safety of the H1N1 vaccines.
For more information:
Barbara Pahud, MD, MPH, can be reached at Children’s Mercy Hospitals and Clinics, 2401 Gillham Road, Kansas City, MO 64108; email: bapahud@cmh.edu.
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