That is a drop of 5% from the 23% protection level that was estimated earlier during the season, said experts from the United States Center for Disease Control. The protection level for children was worse. The CDC medical panel said the effectiveness of the injected form for kids between the ages of 2 and 8 of the vaccine was only 15%.
The nasal spray form of the vaccine might not be protective for young children at all, said health officials.
Studies cannot confirm that the vaccine (nasal) is beneficial, said one doctor from the CDC.
The big worry is why the poor percentage for the vaccine. The low numbers said the CDC is because the flu viruses that currently are circulating are mutated and look different from the strains covered by the vaccine.
The doctor added that the flu strain H3N2 that currently is circulating was not one factored into the season’s vaccine due to decisions about which strains should be targeted that were made in February of last year.
As happens every year, the choices of which strain to be included in the vaccine are made many months in advance so manufacturers of the vaccines have sufficient time to make enough of the vaccines.
In fact, the new H3N2 strain was seen for only the first time in March of 2014 and was not dominant until this past September, which made it much too late to be in the new vaccine.
On Thursday, a recommendation was made by the World Health Organization of which strains to make up the vaccine for next year.
The U.S. Food and Drug Administration next week decides the strains to include in the flu vaccine for next season in the U.S. and usually follows recommendations from the WHO.