ATLANTA — The jury is still out regarding a potential link between the quadrivalent meningococcal conjugate vaccine and Guillain-Barré syndrome, but new data from the Centers for Disease Control and Prevention provide some reassurance in favor of the vaccine's safety.
In October 2006, the CDC published findings from the Vaccine Adverse Event Reporting System (VAERS) that suggested a small increased risk for Guillain-Barré syndrome after receipt of MCV4 (Menactra). In December 2007, the CDC recommended that a history of GBS be considered a “precaution” to administering MCV4 (MMWR 2007;56:1265–6). The package label, meanwhile, was updated to list such a history as a “contraindication,” Dr. Angela Calugar said at a meeting of the CDC's Advisory Committee on Immunization Practices.
The VAERS data had shown that the observed rate of GBS within 42 days after receipt of MCV4 was not elevated among 11- to 19-year-olds overall (33 observed cases vs. 36 expected from background rates), but the rate of GBS did appear to be elevated among adolescents aged 15–19 (26 vs. 20 cases). However, that difference still did not reach statistical significance, said Dr. Calugar of the CDC's Immunization Safety Office.
Since VAERS is a passive reporting system that is used only to generate a “signal” of a possible problem, the CDC undertook an investigation using the Vaccine Safety Datalink (VSD), a collaboration that provides data from 8.8 million members annually.
Between April 2006 and February 2009, 642,493 doses of MCV4 were administered in the eight VSD sites. Among those, five cases of GBS were reported to have occurred in 42 days or less after vaccination. Of those, one had onset of symptoms on day 0, and was therefore out of the “risk window.” Another had pre-existing GBS, and two others were found on further investigation to have diagnoses that were not GBS. The fifth case was still pending medical review at the time of Dr. Calugar's presentation.
But even if that case does turn out to be GBS, one case is the expected background number for the population during the study time period, she noted.
Dr. Carol J. Baker, chair of the ACIP meningococcal working group, added that interim data from a study at Harvard Medical School/Harvard Pilgrim Health Care also have thus far failed to find a link between MCV4 and GBS. That study population included 4.5 million 11- to 18-year-olds, of whom 8% had received MCV4 through May 2007.
Of 240 potential GBS cases identified in claims, none had received MCV4—or any other vaccination—within 42 days. “These are very reassuring data,” said Dr. Baker, professor of pediatrics, molecular virology, and microbiology and head of pediatric infectious diseases at Baylor College of Medicine, Houston.
Dr. Baker stated that she had no disclosures to make.
Interim data from a study of 4.5 million 11- to 18-year-olds also failed to find a tie between MCV4 and GBS. DR. BAKER