Technology & Science

Flu cases didn't drop with Ontario's free shots: study

A study of laboratory-confirmed cases of influenza in Ontario from 1990 to 2005 suggests incidence didn't decrease despite free flu shots. Infectious disease experts say the data used aren't reliable.

Ontario's free vaccine program doesn't appear to have curtailed annual outbreaks of influenza, but some experts are questioning the study's conclusions and the province's lack of record keeping.

Ontario began paying for flu shots for residents in 2000, at a cost of more than $50 million a year.

The goal was to reduce illness and to relieve pressure on emergency rooms that are often inundated with patients during flu season.

Dianne Groll, a professor of health sciences at the University of Ottawa, led the study of all laboratory-confirmed cases of influenza in the province from January 1990 to August 2005.

"Despite increased vaccine distribution and financial resources towards promotion, the incidence of influenza in Ontario has not decreased following the introduction of the UIIC [Universal Influenza Immunization Campaign,]" Groll's team concluded in the journal Vaccine.

But laboratory-confirmed cases of flu are only a small fraction of cases, and aren't reliable from year to year, said Dr. Allison McGeer, head of infection control at Toronto's Mount Sinai Hospital.

"It's not helpful," said McGeer. "You can't look at changes in influenza diagnostics and make any conclusions about what's actually happening."

The study would likely have picked up a huge reduction in flu cases, but the researchers didn't have the needed data to detect a smaller benefit, said Dr. Michael Gardam, an infection control specialist at Toronto General Hospital.

"We've had a couple of years of mild influenza," said Gardam. "What that does is makes it harder to show any benefit of the vaccine. We've also had a couple of years between the vaccine and what was actually circulating out there."

The province didn't keep statistics that would allow the benefits to be measured. It's too bad, because the world is watching Ontario to see if universal vaccines work, he said.

"It is a real tragedy a study with virus identification wasn't set up in advance when the program was put into effect," agreed Dr. Arnold Monto, a noted flu specialist at the University of Michigan.

The study's results may not mean an end to Ontario's universal vaccine experiment, but the findings may make it more difficult to justify the costs of the shots, experts said.

Other studies on the flu shot campaign will be published soon.