Flu viruses are constantly mutating. That makes it difficult to predict which strain to vaccinate against each year.
"That is partly the reason why the flu vaccine is late," said Dr Lee.
In addition, the World Health Organization and the Australian Influenza Vaccine Committee decided that the 2015 southern hemisphere vaccine should contain three seasonal flu strains, not two.
"When available the flu injection will vaccinate against the H1N1, H3N2, and Phuket 3073 viruses," explained Dr Lee.
Unlike the common cold, these flu strains cause serious symptoms. Patients are usually bed ridden with severe aches and pains as well as a blocked runny nose.
"While suffering from the flu is unpleasant, rarely is it life threatening for fit healthy adults," said Dr Lee. "But serious complications can arise for the elderly and people with other chronic health conditions like asthma."
At risk groups should consult their doctor for advice. Vaccines to combat this year's winter flu mutants are expected to be available late April.