"What's not measured is that, even if you get the flu in spite of the vaccine, your flu case is likely to be milder; you're less likely to have the complications of pneumonia, having to be hospitalized and dying", he said.
Added to that uncertainty is the question of how effective this season's vaccine may be in preventing people from getting the flu.
Therefore, do you think it's worth getting a flu shot this year?
As Christmas approaches, health officials are warning Oklahomans that the flu is spreading across the state.
Her advice includes the CDC recommendation to get a flu shot, but she also adheres to low-tech techniques of contagious disease prevention: "good hand-washing techniques, teaching kids not to share their germs, staying home when you're sick and disinfecting common surfaces", she said.
Past year in Canada and the USA, the vaccine was found to be only 35 per cent effective in preventing cases of H3N2 influenza, she said.
"When you get your flu shot it can take up to two or three weeks for your body to fully go through the process".
Flu shot producers expect to make between 151 million and 166 million doses of vaccine this flu season.
Dr. Marc Siegel is an infectious diseases expert from NYU Langone Medical Center in New York City.
"If you're not excited about getting vaccinated yourself, do it for the people you love", Mills said.
"Some patients believe the possible side effects outweigh the positives that they get from prevention", she said. We encourage individuals, and especially seniors, to protect themselves this holiday season with an annual flu vaccine so that they can continue doing the things they love with their families.
Lin, who chaired the meeting, said that doctors have reported that while hepatitis A vaccines have been administered to children older than 12 months, they are not included in subsidies for children's standard vaccinations, which might result in doctors being unable to apply for reimbursement of vaccination costs. Children, pregnant women, and those 65 and older are at particular risk, as are those with chronic lung conditions. Flu vaccines offer lasting protection against the flu for the entire flu season. And in Australia, which used the identical vaccine as Canada's this past season, its effectiveness against H3N2 infection was far less - only about 10 per cent.