The influenza vaccine was “a big disappointment again” this flu season, in the words of the Associated Press, with an overall effectiveness of just 29 percent, according to the Centers for Disease Control and Prevention (CDC).
The flu shot was only about 47 percent, by the CDC’s estimate, for the first part of the season, through mid-February. Things got worse from there, with the shot becoming “virtually worthless” thereafter, to again quote from the AP, with a vaccine effectiveness of just 9 percent.
As the AP further notes, most vaccines “are not considered successful unless they are at least 90% effective”, whereas the “flu vaccine has averaged around 40%.”
Obligatorily, the AP relays the message from public health officials that “the vaccine is still worthwhile since it works against some strains”, but this is a non sequitur fallacy. It does not follow from the fact that the vaccine might offer some protection against some strains of influenza that therefore it is worthwhile.
In fact, the “very high cost of yearly vaccination for large parts of the population” was among the considerations of a 2014 Cochrane meta-analysis that concluded that the results of a systematic review of existing studies “provide no evidence for the utilization of vaccination against influenza in healthy adults as a routine public health measure.”
A randomized controlled trial studying the cost effectiveness of influenza vaccination in healthy adults under aged 65 published in JAMA in 2000 found that this practice “is unlikely to provide societal economic benefit in most years”—when it generated greater costs than to not vaccinate.
Furthermore, studies have shown how getting a flu shot annually can actually increase your risk of influenza illness, as well as other respiratory illnesses.
According to the CDC, the strain of influenza A (H1N1) that emerged during the pandemic year of 2009 dominated circulation in the US through mid-February. But from Mid-February through mid-May, the dominant strain was influenza A(H3N2).
The vaccine fared so poorly against influenza despite the fact that it was designed to protect against both of these strains.