Every year the flu virus does an annual migration across the world, hitting the Southern Hemisphere during its winter, the Northern Hemisphere right about now, and hanging out in the tropics in between — especially in parts of Asia. That means we look to Australia to know what is coming to us... and Australia is seeing one of its worst flu years on record, with over 2½ times more infections than in the same period last year. Influenza A (H3N2) is the predominant circulating influenza A virus this year, and 81% of the confirmed flu deaths have been due to this strain.
U.S. Flu Vaccine Effectiveness Network data for the 2016–2017 influenza season showed this year’s flu vaccine is 48 percent effective in preventing laboratory-confirmed influenza A and B viral infection associated with medically attended acute respiratory illness.
The exact effectiveness estimates are 43 percent against the predominant influenza A (H3N2) viruses and 73 percent against influenza B viruses.