Aug. 25--Preliminary analysis of the vaccine against last season's pandemic influenza A H1N1 vaccine found it was generally as effective and as safe as the seasonal flu vaccine.
Although one vaccine monitoring system did turn up "weak" evidence of an association with a temporary facial paralysis called Bell's palsy, that association has yet to be proved on further analysis, an official cautioned.
Also, after reports of seizures in children who received one brand of the current seasonal flu vaccine, officials are recommending that brand generally not be used in children 8 and younger.
In a briefing Tuesday, officials with the Centers for Disease Control and Prevention outlined vaccine safety efforts from last flu season, when the novel vaccine underwent extraordinary and expanded monitoring.
Compared to the previous year's vaccine, the H1N1 vaccine proved just as effective, said Dr. David Shay, the team leader in the epidemiology and prevention branch in the influenza division at CDC.
Pandemic H1N1 is now incorporated in this season's flu shot.
In a monitoring system called the Vaccine Safety Datalink, the 1.3 million flu shots studied produced a "weak signal" that there was a slightly increased risk of Bell's palsy, said Dr. Karen R. Broder, the acting team leader for the surveillance and public health response team in the Immunization Safety Office at CDC. However, none of the other monitoring systems showed that, and neither did some further analysis, she said.
"It wasn't occurring in all of the different analyses and on further analyses it's looking like it's not persisting," Broder said.
Overall, there was not an increased risk for seizure or Guillain-Barre syndrome, where the body attacks the peripheral nervous system, she said. Guillain-Barre was associated with a 1976 flu vaccine, but in seasonal flu vaccines since there has been a low increased risk of 1 case per million vaccinated.
In one monitoring system added last year called the Emerging Infections program, the H1N1 vaccine was associated with roughly a 1-case-per-million increased risk that was not shown in others, Broder said.
"This is very similar to the level of risk that has been observed in some studies over the years for seasonal influenza vaccine and (Guillain-Barre)," she said.
However, the recommendations for a shot called Afluria were changed after some children younger than 5 in Australia had febrile seizures after receiving the shot this summer, Broder said.
The shot is not recommended for those younger than 4 now and generally shouldn't be given to those younger than 8 unless there is a compelling need and it is discussed with the parents, she said.
Most physicians and providers should know about the changed recommendations for that brand, made by CSL Biotherapies Inc. Other brands have not provoked this in children; however, the CDC and other agencies plan to do increased monitoring for febrile seizures, Broder said.
The CDC is recommending that everyone from age 6 months on get the flu shot this year, when 160 million to 170 million doses are expected.
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