Using numbers to explain vaccine benefits

Photo: Sanofi Pasteur via Flickr

Do you wrestle with ways to illustrate numbers when writing about vaccines?

Dr. Gretchen LaSalle, a family physician in Spokane, Wash., recently offered some ways to do this effectively in a blog post called Vaccine Data: Do the Math.

LaSalle skillfully highlights two examples of how numbers can be used. In one example, related to flu figures, she suggests how real-life context can make the risks of the flu more obvious. In another example, related to measles data, she underscores how numbers can be used to mislead.

With the flu, the number of annual deaths generally is met with a shrug by the public.

On average, 12,000 to 56,000 people die of the flu each year and around 80,000 died in the 2017-2018 flu season, including 186 children, according to the Centers for Disease Control and Prevention.

But when LaSalle talks with her adult patients about getting a flu shot and the potential danger of the flu, some of her patients tell her that 80,000 deaths “is not that many.” There is some truth to this, in that from a purely statistical standpoint 80,000 deaths in the United States [with a population of about 326 million] is around 0.024 percent. Through this prism, flu deaths do seem to be nothing to worry about.

But another way to tell the story of flu death figures is by creating drama.

Thinks of a news headline like: “The entire sold-out crowd of the New York Giants’ Met Life Stadium died of the flu yesterday” or “Eighty thousand people died when 152 Boeing 747 jetliners crashed, killing everyone on board. The cause: influenza,” LaSalle asks.

Using numbers in this way, might grab people’s attention and help them visualize and connect with what 80,000 deaths mean emotionally, she says.

“We respond to data in much the same way that we respond to events in our lives — emotion comes before reason,” she wrote.

If a reader can imagine themselves or someone they love being one of those audience members in Giants’ stadium or a passenger on that crashed 747, then maybe they might consider getting a flu shot. Only about half of adults and about 60 percent of children get the flu shot annually. The majority of the children who died from the flu during the 2017-2018 flu season didn’t get a flu shot.

Still, reporters have to be careful with how they choose to create a picture because numbers can be used to create misleading visualizations, too, she says.

To highlight this point, LaSalle points to two graphics on measles that use similar numbers but have a very different meaning.

In one graph, which utilizes CDC data on both measles cases and deaths from measles, one can see that after the measles vaccine was introduced in 1962 there was a sharp decline in cases and deaths.

In another graph, which only utilizes mortality data from measles, the illustration suggests that the measles vaccine had minimal impact on public health. That graph was published by vaccine opponents.

Though few people were dying of measles in 1962, hundreds of thousands of people developed measles, and symptoms from the measles include brain swelling, pneumonia and potentially life-long health problems.

“When it comes to numbers and data, emotional reactions (and first impressions) can sometimes lead us astray,” she says.

This is why reporters always have to dig deeper when presenting numbers and considering how they can be illustrated in their stories.

To read more about how to use numbers in stories, take a look at our medical studies section, and to learn more about covering infectious diseases, check out our infectious diseases section. LaSalle’s blog site also regularly offers ideas on how to debunk misinformation from vaccine opponents.

One thought on “Using numbers to explain vaccine benefits

  1. Avatar photoDan Keller

    These same principles apply to firearm injuries and deaths. Often, the numbers are presented as deaths. Injuries are not to be ignored. They are not benign and can cause significant lifelong morbidity, with ramifications for disability, earning potential, family disruption, and quality of life. The answers you get depend on the questions you ask.

Leave a Reply