Until the 2002-2003 influenza season, the only licensed influenza vaccine in the United States was the inactivated, trivalent injectable vaccine. In June 2003, the U.S. Food and Drug Administration (FDA) licensed a trivalent live, attenuated influenza vaccine (LAIV-T) for intranasal use among healthy persons 5 to 49 years of age. Although the number of vaccinees studied during prelicensure LAIV-T clinical trials was relatively large (20,228), postlicensure administration of the vaccine to much larger populations could reveal new safety issues.

Hector S. Izurieta, M.D., M.P.H., of the Food and Drug Administration, Rockville, Md., examined the adverse events reported to the U.S. Vaccine Adverse Event Reporting System (VAERS) during the first 2 influenza seasons following LAIV-T licensure to identify new or unexpected adverse events, including rare events.

Approximately 2,500,000 persons received LAIV-T during the first 2 postlicensure seasons. As of August 16, 2005, VAERS received 460 adverse event reports for vaccinations. No fatalities were reported. There were 7 reports of possible anaphylaxis, 2 reports of Guillain-Barré syndrome, 1 report of Bell palsy, and 8 reports of asthma exacerbation among individuals with a prior asthma history. Events in individuals for whom the vaccine was not indicated accounted for 73 reports.

“Reports to VAERS in the first 2 seasons of LAIV-T use did not identify any unexpected serious risk with this vaccine when used according to approved indications. Like many vaccines and other medical products, LAIV-T may rarely cause anaphylaxis. As with other vaccines, LAIV-T could carry the risk of anaphylaxis or other allergic events. Continued monitoring of neurological events, such as GBS, appears warranted. Determination of the risk of secondary transmission of the vaccine virus would require a focused clinical study,” the authors write.

MEDICA.de; Source: American Medical Association (AMA)