When the Canadian province of Ontario began offering free flu vaccinations to its entire population in 2000, the result was a dramatic decrease in influenza-associated antibiotic prescriptions.

Dr. Fawziah Marra, of the University of British Columbia in Vancouver, and colleagues analyzed rates of flu-associated antibiotic prescriptions in Ontario before and after free immunization became available. The results were compared with data from other provinces, where vaccine programs continued to target high-risk groups and their contacts.

From the beginning of the study period to the end (1997-2007), overall vaccine use rose from 18 percent to 38 percent in Ontario and from 13 percent to 24 percent in other provinces, the researchers report.

They also report that across Canada, rates of respiratory antibiotic prescriptions generally decreased after 2000.

However, after the introduction of universal flu immunization in Ontario, rates of influenza-associated antibiotic prescriptions in that province fell 64 percent, from 17.9 to 6.4 per 1000 people, compared with a non-significant decline from 8.3 to 8.2 per 1000 people in other provinces.

This 64 percent relative reduction translates to approximately 144,000 respiratory antibiotic prescriptions 'prevented' by the universal vaccination program each year, the investigators maintain.

Before 2000, flu-related antibiotics accounted for 2.7 percent of the nearly 22.8 million total annual respiratory antibiotic prescriptions in Ontario, whereas after 2000 they represented only 1.1 percent of the nearly 50.2 million total.

In the other provinces combined, however, the corresponding percentages remained unchanged (1.4 percent of 34 million prescriptions before 2000 and 1.5 percent of 76 million afterward).

These findings, they say, shows that Ontario flu vaccination program has public health and clinical relevance, indicating the potential for universal influenza immunization to reduce influenza-associated antibiotic utilization.

SOURCE: Clinical Infectious Diseases, September 1, 2009.