Why this year’s flu virus is tougher than usual

If it seems like everybody you know has or has had the flu recently, you’re not too far wrong. The CDC confirms that flu activity is currently widespread in most of the U.S.

Flu viruses are constantly changing so it’s not unusual for new flu viruses to appear each year, which keeps the CDC busy trying to anticipate the types of vaccinations that will be needed and make sure they are in sufficient supply. The CDC reviews and updates the composition of vaccines to match – as much as possible – whatever flu viruses are circulating.

Vaccines do triple (or more) duty

Flu vaccines protect against the three or four viruses (depending on vaccine) that research suggests will be most common. For 2017-2018, three-component vaccines are recommended to contain:

an A/Michigan/45/2015 (H1N1)pdm09-like virus (updated)
an A/Hong Kong/4801/2014 (H3N2)-like virus
a B/Brisbane/60/2008-like (B/Victoria lineage) virus
Quadrivalent (four-component) vaccines, which protect against a second lineage of B viruses, are recommended to be produced using the same viruses recommended for the trivalent vaccines, as well as a B/Phuket/3073/2013-like (B/Yamagata lineage) virus.

Rapid changes

Unfortunately, the flu vaccine is less effective with the “A” viruses that are affecting so many people this year. One reason for that is because genetic changes occur in A(H3N2) viruses so frequently that between the time when the composition of the flu vaccine is recommended and the flu vaccine is delivered, H3N2 viruses are likely to have changed in ways that could impact how well the flu vaccine works.

Nonetheless, says the CDC, “Getting an annual flu vaccine is still the first and best way to protect yourself and your family from the flu. Flu vaccination can reduce flu illnesses, doctors’ visits, and missed work and school due to flu, as well as prevent flu-related hospitalizations. In 2017, a study in Pediatrics was the first of its kind to show that flu vaccination also significantly reduced a child’s risk of dying from influenza. The more people who get vaccinated, the more people will be protected from flu, including older people, very young children, pregnant women, and people with certain long-term health conditions who are more vulnerable to serious flu complications.”

Only injectable flu vaccines (flu shots) are recommended. Live attenuated influenza vaccine (LAIV) – or the nasal spray vaccine – is not recommended for use during the 2017-2018 season because of concerns about its effectiveness. Some flu shots protect against three flu viruses and some protect against four flu viruses.

Options this season include:

Standard dose flu shots. Most are given into the muscle (usually with a needle, but one can be given to some people with a jet injector). One is given into the skin.
High-dose shots for older people.
Shots made with adjuvant for older people.
Shots made with virus grown in cell culture.
Shots made using a vaccine production technology (recombinant vaccine) that does not require the use of flu virus.

There is a table showing all the flu vaccines that are FDA-approved for use in the United States during the 2017-2018 season.