Sunday, October 18, 2009

The Guillain-Barré syndrome and the 1992-1993 and 1993-1994 influenza vaccines/ NEJM

As I've said previously, before the 2009 swine flu came along, public health officials knew that vaccinations sometimes led to small increases in cases of GBS.  GBS cases (above baseline incidence levels) were not limited to the 1976 swine flu vaccine, but have occurred after other vaccines, although less commonly.

During the 1992-3 flu season, the incidence of GBS roughly doubled in flu vaccine recipients during the six week period following vaccination, according to a 1998 article in the New England Journal of Medicine by CDC and U Maryland authors:
BACKGROUND: The number of reports of influenza-vaccine-associated Guillain-Barré syndrome to the national Vaccine Adverse Event Reporting System increased from 37 in 1992-1993 to 74 in 1993-1994, arousing concern about a possible increase in vaccine-associated risk. METHODS: Patients given a diagnosis of the Guillain-Barré syndrome in the 1992-1993 and 1993-1994 influenza-vaccination seasons were identified in the hospital-discharge data bases of four states. Vaccination histories were obtained by telephone interviews during 1995-1996 and were confirmed by the vaccine providers. Disease with an onset within six weeks after vaccination was defined as vaccine-associated. Vaccine coverage in the population was measured through a random-digit-dialing telephone survey. RESULTS: We interviewed 180 of 273 adults with the Guillain-Barré syndrome; 15 declined to participate, and the remaining 78 could not be contacted. The vaccine providers confirmed influenza vaccination in the six weeks before the onset of Guillain-Barré syndrome for 19 patients. The relative risk of the Guillain-Barré syndrome associated with vaccination, adjusted for age, sex, and vaccine season, was 1.7 (95 percent confidence interval, 1.0 to 2.8; P=0.04). The adjusted relative risks were 2.0 for the 1992-1993 season (95 percent confidence interval, 1.0 to 4.3) and 1.5 for the 1993-1994 season (95 percent confidence interval, 0.8 to 2.9). In 9 of the 19 vaccine-associated cases, the onset was in the second week after vaccination, all between day 9 and day 12.
: There was no increase in the risk of vaccine-associated Guillain-Barré syndrome from 1992-1993 to 1993-1994. For the two seasons combined, the adjusted relative risk of 1.7 suggests slightly more than one additional case of Guillain-Barré syndrome per million persons vaccinated against influenza.
In 2004, CDC scientists reported that, "Guillain-Barré syndrome remains the most frequent neurological condition reported after influenza vaccination to the Vaccine Adverse Events Reporting System (VAERS) since its inception in 1990."

A separate 1979 review of GBS cases found 532 people developed GBS shortly after swine flu vaccination. Canadian data questionably found a slight increase in GBS 2-7 weeks after flu vaccinations over many flu seasons.

From the Sept. 2009 Journal of Clinical Neuromuscular Diseases comes a study of GBS reports to VAERS.  The authors concluded, "Our results suggest that vaccines other than influenza vaccine can be associated with GBS."

CDC was concerned about the Menactra (meningitis) vaccine and GBS; see the MMWR on this subject. The WHO agreed that a small increased risk of GBS existed from meningitis vaccine.

Thus the link between GBS and vaccination has clearly been established, and acknowledged by CDC, despite obfuscation recently in the media.

1 comment:

Alan said...

"CDC Encourages Flu Shots, Dispels Fears" Read it at