November 7, 2017 — The flu vaccine was only 48% effective during the 2015-2016 winter flu season, according to a study published in the New England Journal of Medicine.
The key findings of the study were that overall effectiveness of all flu vaccines was 48% during the 2015-16 flu season.
Unfortunately, the live attenuated influenza nasal spay (Flumist®) did even worse. It had zero effectiveness for children between the ages of 2 and 17 years old. After other studies showed similar results, that’s why FluMist® was not recommended for use in the United States.
The relatively low rate of flu vaccine effectiveness may be alarming. The 48% effectiveness is much lower compared to other vaccines, where doctors routinely expect effectiveness above 90% or more.
So why do accept such low vaccine effectiveness in flu shots? Part of the reason is that influenza is potentially deadly.
In high-risk patients — especially children and people with breathing problems — the flu is often so severe that patients must be hospitalized for medical care.
Another benefit of flu vaccination is protection against more serious illnesses. The vaccine often reduces the risk of hospitalization or death, especially in very high-risk individuals.
Universal immunization helps protect the highest-risk people in a community via herd immunity. So, while it would be great to have flu shot effectiveness above 90%, a lower but still significant effectiveness is beneficial for the highest-risk individuals.
Source: Jackson ML, Chung JR, Jackson LA, et al. Influenza vaccine effectiveness in the United States during the 2015-2016 season. N Engl J Med. 2017;377(6):534-543; doi: 10.1056/NEJMoa1700153.