Skip to main content

All Access Subscription

Get unlimited access to our full publication and article library.

Get Access Now

Interested in Group Sales? Learn more

HI Cprevent logo small


This award-winning blog supplements the articles in Hospital Infection Control & Prevention.

Poor Match Between Flu Shot and H3N2 Strain Reveals a Serious Need for a New Flu Vaccine

A recent report by the Centers for Disease Control and Prevention — noting that this season’s flu vaccine is only 23% effective at keeping people from seeking medical care — comes as no surprise. We have a classic mismatch problem, as the predominant circulating strain of H3N2 influenza A is not covered in the vaccine.

During seasons when vaccine viruses and circulating influenza viruses are well matched, vaccine efficacy is between 50%-60%, the CDC reports. There is an H3N2 virus in the vaccine, but antigenic drift created an H3N2 splinter strain that eludes immunization protection. This strain comprises about 70% of the circulating H3N2, which is the predominant flu virus this season. Antivirals will certainly knock it back if you get them administered during the early course of illness.

“Flu viruses change constantly and the drifted H3N2 viruses did not appear until after the vaccine composition for the Northern Hemisphere had been chosen,” the CDC stated.

Such are hazards of the longstanding flu vaccine forecast and production methods, and again we are reminded of the need for a better method to this madness before the next pandemic appears. In a controversial 2013 report , the Center for Infectious Disease Research & Policy (CIDRAP) at the University of Minnesota in Minneapolis took the CDC to task for widely promoting vaccine uptake while downplaying the limited efficacy of the seasonal vaccine.

Saying that new vaccine development be given a priority akin to the Manhattan Project, CIDRAP cited both the ongoing toll of seasonal flu and the recurrent threat of pandemic strains. An estimated 3,000 to 49,000 individuals in the U.S. die every year from seasonal influenza. The World Health Organization estimates seasonal influenza causes three to five million cases of severe illness worldwide and about 250,000 to 500,000 deaths annually, CIDRAP states. A pandemic strain raises the stakes considerably, as many lives will be lost before an effective vaccine can be created. Four pandemics have occurred in the modern era: 1918, 1957, 1968, and 2009.

Given the inevitably of another pandemic, CIDRAP says we can ill afford to be complacent with the current state of flu vaccines. Quoting historian Daniel Boorstin, the report warns that “The greatest obstacle to discovering the shape of the earth, the continents, and the oceans was not ignorance but the illusion of knowledge.”