Of those in Sweden who have had the flu shot, including the elderly and pregnant women, only three percent are said to run a lower risk of catching the flu.
Helene Englund at Folkhälsomyndigheten (the Public Health Agency of Sweden), tells news agency TT that the poor defence against the virus is because the vaccine was produced in February last year and the latest flu virus has changed since then.
"The vaccine does not match the strain which is circulating," she says to TT.
The World Health Organisation makes recommendations on the strains of flu to be used in vaccines each year but it takes six months to produce enough quantities, by which time changes in the virus can have occurred.
Helene Englund still advises people in the risk groups, such as the elderly and pregnant women, to have the jab.
"It is still important for those at risk to take the flu jab. The vaccine can still alleviate symptoms and prevent serious illness or death (from secondary infections)."
The same vaccine has been given in the UK where the British public health authority first made the analysis that revealed the vaccine's poor protection. In the UK, the numbers of deaths among people over 65 has risen by over 40 percent in two weeks of January this year, compared to the same period last year.