In a new study published in the journal Vaccine, Dr. Annette Regan, of the Texas A&M School of Public Health, and colleagues from institutions in the U.S. and Australia examined the effectiveness of the influenza vaccine in Australia during the 2016 Southern Hemisphere influenza season. They were specifically interested in examining the effectiveness of vaccination as the seasonal epidemic progressed. To accomplish this, the researchers relied on data from three health care surveillance systems in Australia. They found more than 5,000 patients who had influenza-like symptoms; 1,085 of these patients were tested for influenza, and 447 tested positive for influenza. The data also included a breakdown of which strain of influenza each patient had along with patient demographic information and when, if at all, patients had received a vaccination. Patients with influenza-like illness who tested negative for influenza were used as a control group in calculating vaccine effectiveness.
Their analysis found that the 2016 influenza vaccine in Australia had an overall effectiveness of 40 percent. Vaccine effectiveness for specific strains ranged from 42 to 67 percent for different influenza A viruses, but the 2016 vaccine was ineffective against influenza B viruses. Dr. Regan and colleagues also found that the vaccine was most effective in patients with a record of vaccination less than three months before symptom onset. Vaccine effectiveness at three months after vaccination was approximately 40 percent and that effectiveness declined after that, with a 25 percent effectiveness at four months, suggesting vaccination as close to the influenza season may provide optimal protection.Tags: Friday Letter Submission