(NaturalNews) The 2007-08 flu vaccine was only 44 percent effective, the Centers for Disease Control and Prevention (CDC) has admitted in a study published in Morbidity and Mortality Weekly Report, making the flu season the worst since 2003-04.
Flu vaccines are formulated based on health officials' educated guesses about which strains of the virus are most likely to be circulating in a given year. Three of these strains are picked for inclusion in the vaccine. When officials guess correctly, the vaccine is usually between 70 and 90 percent effective.
This past year, however, most flu infections were caused by a Type A H2N2 Brisbane strain that was not included in the vaccine. Another common infectious agent was a Type B Florida strain. According to data collected by the Marshfield Clinic in central Wisconsin, the 2007-08 flu vaccine was only 58 percent effective against the Brisbane strain and totally ineffective against the Florida strain.
Researchers usually measure the severity of a flu season by comparing either adult or child mortality data. By both measures, the 2007-08 season was the worst in three years.
In the 2003-04 season, the flu vaccine also failed to function at peak effectiveness, due to the primary infectious agent for that year not being included.
As of the time of the study's conclusion, 66 children had died from the 2007-08 flu season, compared with 153 in 2003-04. Similarly, adult death from flu or pneumonia accounted for a high of 9 percent of all reported deaths in March 2008, compared with a high of 10 percent in the 2003-04 season. These deaths were at levels high enough to pass the epidemic threshold for 13 consecutive weeks in the most recent season, however, four more weeks than in 2003-04.
"Our season is not quite as high but is lasting a little longer," said Dan Jernigan, deputy director of the CDC's influenza division.