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The Journal Gazette

Tuesday, October 03, 2017 1:00 am

Healthy debate

Let's talk about vaccines, but not the way you're used to

Christer Watson

Every time I read in the papers about vaccines, it seems to be some variation on people being worried about them despite overwhelming evidence of how they keep us healthy. Often, those opposed to vaccinations claim just to be skeptical, or they want more debate. Unfortunately, it is hard to convey how much that argument does not look like a scientific debate. I think to get a flavor of why that is true, it is helpful to see what an actual scientific debate about vaccines looks like.

For example, I was reading in the journal Science about the flu vaccine. I expect the story was timed for start of flu season. Nonetheless, it was fascinating to learn about the difficulties in developing good flu vaccines.

Before those details, however, it is worth emphasizing the importance of getting a flu vaccine. The flu is more than inconvenient. Last year, it killed about 60,000 people in the U.S. As a comparison, heart disease, the most deadly U.S. disease, killed about 600,000. The flu is deadly and important, and the best current way to reduce these fatalities is for everyone who is able to get a flu vaccine.

With that out of the way, the flu vaccine is not as effective as we would like. Recent studies appear to show that between 10 percent and 60 percent of people who receive a flu vaccine show evidence of flu protection. That is much lower than we believed a couple of decades ago. The reason for the change toward pessimism is that we can better measure the presence of small amounts of the flu virus in large-scale studies.

The main reasons the vaccine doesn't protect more people is because of mutations, but not the mutations we used to think were a problem. That is, scientists used to think the flu virus mutated during a flu season, so the specially designed vaccine wasn't as effective against the mutated flu viruses. It appears, however, that other mutations may be more important. Danuta Skowronski, a researcher at the British Columbia Centre for Disease Control, has shown that the vaccine can mutate as it is grown for distribution. These mutations could be making the vaccine less effective.

There are other complications, however, that also make good vaccine development hard. For example, a person's history of exposure to the flu, especially their first exposure, matters. Apparently a person's immune system keeps an especially strong memory of this first exposure.

During the 2013-14 flu season, middle-aged people caught the flu in larger than typical numbers. This appeared to happen in middle-aged people who had gotten the vaccine. Viral immunologist Scott Hensley, at the University of Pennsylvania, showed that the middle-aged people's immune system appeared to have been tricked. The vaccine that year was similar, but not identical, to a flu variation that was common when these people were children. As a result, their immune systems didn't learn enough from the vaccine and tried to fight the older variation.

So a vaccine that was pretty effective for many people didn't work for these middle-aged people. That is a bit of a nightmare if a scientist is aiming to design vaccines to be nearly universally effective.

So this is the debate. What sort of mutation is reducing the flu vaccine's effectiveness? Or is the problem something related to a person's immune system history?

It isn't melodramatic and it doesn't involve people with conflicting values. It involves people changing their mind about how effective the flu vaccine is, then trying to figure out how to fix that problem. This is a useful vaccine debate.

 

Christer Watson, of Fort Wayne, is a professor of physics at Manchester University. Opinions expressed are his own. He wrote this for The Journal Gazette, where his columns appear the first and third Tuesday of each month.