Safety of Acellular Pertussis Vaccines Confirmed by Drop in Adverse Events
WESTPORT, CT (Reuters Health) Oct 4 - Acellular pertussis vaccines, the first of which was licensed in the US in 1996, show a significantly better safety profile than whole-cell pertussis vaccines, report investigators from the Food and Drug Administration and the Centers for Disease Control and Prevention.
Dr. M. Miles Braun of the FDA in Rockville, Maryland, and associates evaluated reports to the Vaccine Adverse Event Reporting System (VAERS). Reports of events after immunization declined significantly "during the transition from nearly exclusive use of whole-cell pertussis vaccine in 1995 to predominant use of acellular pertussis vaccine in infants in 1998," the investigators report.
The number of "less serious reports" dropped from 1652 during 1995 to 357 for the first half of 1998, and the corresponding number of reports for "nonfatal serious events" declined from 334 to 93.
"This analysis did not detect any adverse event term that showed a substantial and clinically meaningful higher frequency" for acellular pertussis vaccines than for those containing whole-cell vaccines, Dr. Braun's team writes in the online version of the October issue of Pediatrics.
The same issue of Pediatrics contains another article by Dr. Braun and associates, indicating a decline in the number of reports of hypotonic-hyporesponsive episodes attributed to pertussis vaccine since 1996.
In what the authors call "the largest published case series of children with hypotonic-hyporesponsive episodes," there were 215 cases identified between 1996 and 1998. Such episodes were associated with pertussis-containing vaccine 93% of the time. However, they write, this syndrome "will continue to be reported because it also occurs after administration of vaccines other than whole-cell pertussis."
The investigators describe the syndrome as "generally benign, self-limited, nonrecurrent." Only three children did not return to their pre-vaccination state, but in each case, the condition reported to VAERS was not known to be causally associated with immunization.
No further adverse events were reported for the 24.1% of children who were subsequently re-immunized with acellular pertussis.