18 June 2018

Experts spring to defence of flu vaccine

Clinical Immunology

Immunisations experts have defended Australia’s flu vaccination program at a meeting in Adelaide, after criticisms based on a Cochrane review were splashed across the media. 

Speaking at the Adult Immunisation Forum in Adelaide earlier this month, Immunisation Coalition chairman and infectious diseases epidemiologist, Professor Paul Van Buynder said: “We have our own special Australians. They are part of the Cochrane Collaboration. 

“I’m ashamed to admit it, but one of them lives on the Gold Coast where I am, and he’s been in the news recently saying, ‘Let’s face it. Flu vaccines are useless. No one should have a flu vaccine. Instead, everybody should wear a face mask for all of winter.’ 

“Clearly, that’s damaging for the influenza program overall.”

These criticisms, first reported by The Medical Republic, were made by Professor Chris del Mar at the GPs Down Under conference this month, and were backed by Professor Peter Collignon, an infectious disease physician at ANU.

Professor del Mar, a public health expert at Bond University, quoted a Cochrane review, which showed that the flu vaccine only reduced the rate of influenza in the population from 2% to 1%. 

Annual influenza vaccination did little to prevent serious illness, he said. “It looks to us like the emperor has no clothes.”

The experts at the Adult Immunisation Forum reinforced the importance of the flu vaccine as a potentially life-saving measure in young children, the frail elderly and pregnant women.

“This is flu in pregnancy if you are unlucky,” Professor Van Buynder said, pointing to a slide with an image of a women hooked up to ECMO in intensive care. “This lady was towards the end of her second trimester, the baby was pulled out and didn’t survive, she was incubated, and she stayed on the ECMO machine for weeks.”

Last year, a Melbourne woman caught the flu while pregnant and went into a coma,  Professor Van Buynder said. 

It was only when the 33-year old mother woke three months later that she actually got to meet her baby for the first time.” Influenza is not a benign disease,” said Professor Van Buynder. “[It’s] is a nasty disease and we need to stop people getting it.” 

It might seem like the flu vaccine was not very effective in older people, but many observational studies underestimated the benefit, Professor Shelly McNeil, the chief of the Division of Infectious Diseases at the Nova Scotia Health Authority in Canada, said.

Observational studies of flu vaccine effectiveness often suffer from various forms of bias. Unlike RCTs, people in observational studies are not randomly assigned treatments; they self-select whether to receive the flu vaccine or not. In younger populations, the people who take the most care of their health are more likely to get vaccinated, which makes the flu vaccine look more effective than it actually is.

The same thing happened in observational studies of older populations, but the bias went in the opposite direction, Professor McNeil said. 

Frail older people were more likely to be vaccinated against the flu than healthy older adults, but they were also more likely to get sick, which meant the flu vaccine looked less protective than it actually was. 

Before Professor McNeil adjusted for frailty, the vaccine was 45% effective in preventing hospitalisation in older adults.

Once frailty was taken into consideration, this figure jumped to 58%. 

“Even if the vaccine is only 30 to 50% effective, it is going to do you more good to get it than not,” Professor Robert Booy, a pediatrician and the head of the clinical research team at NCIRS, said.