The efficiency of the flu jab has been under the microscope.

A New Zealand Medical Journal article has looked into its effectiveness, and how to make it more effective.

Director of the Immunisation Advisory Centre at Auckland University, Dr Nikki Turner, says the latest research shows the vaccine is between 60 and 70 percent effective.

"It varies from year to year depending on whether the vaccine was a good match for the circulating strain."

Dr Turner says pregnant women should seriously consider getting the vaccine to protect them and their unborn child.

"A pregnant woman who is vaccinated will pass protection to their newborn child for the first few months of life."

In 2014, 27 percent of the population got the flu jab.