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 following receipt of MCV4 (Menactra), 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 between the agency and eight managed care organizations that provide data from 8.8 million members annually, approximately 3% of the U.S. population.
Between April 2006 and February 2009, a total of 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 following 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.
Still the CDC remains vigilant, and is continuing to monitor for GBS reports following receipt of MCV4 vaccine through both VAERS and VSD, she said.
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, just 100 had sufficient information to determine claim status, and 29 met the primary study end point definition. 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.
“The Harvard Pilgrim analysis has been completed. I am fairly certain we will have these data in June, and I hope that this will put to rest the GBS safety issue,” she said in an interview following the meeting.
This has implications because 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. Calugar said.
Dr. Baker stated that she had no disclosures to make.
“These are some very reassuring data,” Dr. Carol J. Baker said of interim study findings on the subject. ©Parker Clayton Smith
Other Meningococcal Vaccination Issues
The meningococcal working group will present ACIP with information on the duration of protection of MCV4 and the introduction of a second meningococcal conjugate vaccine later this year, Dr. Baker said.
When Sanofi Pasteur's Menactra was recommended in 2005 for use in 11- to 12-year-olds as part of the adolescent vaccination visit, it was assumed that the vaccine would protect for at least 10 years, including the high-risk college years. However, “there were no data then and the 5-year data [now] suggest that 10 years may not be realistic. We hope to have more data in June,” Dr. Baker said in an interview after the meeting.
The current recommendation for revaccination with the meningococcal polysaccharide vaccine is 3-5 years, and a revaccination recommendation may be necessary for MCV4 as well. “Meningococcal conjugate vaccines are unlikely to provide lifelong protection,” she said during the meeting.
Later this year ACIP also is expected to hear immunogenicity data for a new quadrivalent meningococcal conjugate vaccine, Novartis's Menveo, which is expected to be licensed in the summer of 2009. Its composition is different from that of Menactra, and it is not known yet whether or how that might impact duration or degree of protection, Dr. Baker said in the interview.