Last week, the CDC reported that this year’s flu vaccine may not be as effective as they had hoped, because it’s not a perfect match for the specific strains of the virus circulating in the US. But that doesn’t mean this year’s vaccine doesn’t do any good. If you haven’t gotten a flu shot yet, you should definitely still get one.
Every year, the flu vaccine is designed to protect against a handful of strains that experts expect to make the rounds during the upcoming season. One of this year’s strains, called H3N2, has mutated just enough that the standard vaccine no longer protects against it.
The flu vaccine is never perfect though, and there’s always a chance you could still get sick. But if you did get the vaccine and then happen to catch one of those offbeat strains, you won’t get as sick. Allison Bartlett, MD, Associate Medical Director of the Infection Control Program at the University of Chicago, spoke to ABC 7 Chicago last week about how this works:
“In the past when that has happened, although the vaccine hasn’t been perfectly effective, it has helped. So people may still get the flu, but they’ll get much less sick than they would have.”
Since the late 1970’s, three major strains of influenza have circulated through human populations: H3N2, H1N1 (or “swine flu”), and B. From one season to the next, one or the other might be more prevalent. Researchers know that, say, if it’s a big H3N2 season, then the H1N1 and B strains tend to be less widespread, or vice versa.
This year, H3N2 and its variations are in the lead. Last year, when H1N1 was the primary strain, we spoke to Sarah Cobey, PhD, an assistant professor in the Department of Ecology and Evolution, about the work she’s doing to analyze historical data on how these viruses compete. The hard part of predicting how this works is that the different flu strains not only compete with each other for human hosts, but other bugs like whooping cough, measles and the common cold:
“There are a lot of complex patterns that different diseases display, like how influenza tends to peak in the winter, and certain winters are dominated by certain strains,” Cobey said. “But we don’t really have a great way at this point to infer at the population level which of these forms of competition, or which of these interactions, are important.”
And any time we talk about the effectiveness of the flu vaccine, it’s important to remember that you don’t get a flu shot just to protect yourself; You do it to protect others around you. When Dr. Bartlett spoke with NBC 5 Chicago’s Tammy Leitner this spring about a troubling state report showing low vaccination rates in some Illinois schools, she described this concept of “herd immunity”:
It’s critical that every child who can be vaccinated, should be vaccinated. There are some important exceptions in kids who shouldn’t be vaccinated: children with cancer whose immune systems aren’t working, children who are born with immune system problems, and some young infants that just aren’t old enough to be vaccinated. So it’s our duty for everyone else to be vaccinated to protect the people who really truly cannot be vaccinated.
One of the reasons that we’ve been so successful at eradicating some of these diseases is that we have something called herd immunity. This basically means that even though not every vaccine is 100 percent effective, and we know that 100 percent of people can’t be vaccinated, as long as the overwhelming majority of people are vaccinated and respond to the vaccine, the community is kept safe.