This child was not vaccinated. (AP Photo/Universal Pictures, Laurie Sparham)
This child was not vaccinated. (Universal Pictures, Laurie Sparham/Associated Press)

Good news! The people of Twitter are preserving their herd immunity to nonsense non-science.

Jenny McCarthy, a personality on “The View” best known on the Internet for her completely bogus and unscientific and harmful and problematic opposition to vaccinations, recently presented the Internet with some lovely sluggish barrel-fish, and the Internet dutifully shot them.

“What is the most important personality trait you look for in a mate? Reply using #JennyAsks,” McCarthy tweeted.

Tweeters were quick to seize the opportunity that had been handed to them on a large golden platter, garnished with parsley and with an apple stuck in its mouth.

The hashtag was instantly hijacked by people promoting vaccination.

(Phil Plait, at Bad Astronomy, has a good selection.)

This is great and encouraging, if you like science. But there is one problem with the backlash. Actually, there’s two: it makes it seem as though this is a debate, however one-sided, and it just preaches to the choir. The choir hears someone saying “Hey, can you believe that in 2014, some crazy person still believes the earth is flat?” But someone else hears, “Some people still believe the earth is flat. Others call them ‘crazy.’ ” Every time the Round Earthers resoundingly win a debate, you perpetuate the notion that it’s a debate, not a set of facts that are simply not up for discussion.

This is probably making a mountain out of a little good-natured Twitter fun. Still, it’s worth considering every time you “win” an argument over a fact that you SHOULD NOT EVEN BE ARGUING ABOUT IN THE FIRST PLACE. How do you counteract misinformation, then? I wish I knew.

Vaccination depends on herd immunity. Twitter is a big herd (more than 600 million, last time I checked) and those shouting McCarthy down within it are a big herd. But they’re not the ones we have to worry about. The mere existence of a movement of doubters large enough to justify the name anti-vaxxers — you don’t name a movement that doesn’t exist — bodes badly.

And convincing those who don’t already believe is more of an uphill battle than we realized. It takes more than a little well-placed snark. Consider this study, published in the journal of the American Academy of Pediatrics, which tried four different methods of convincing parents of young children to vaccinate their kids for measles, mumps and rubella — information about the lack of a link between the vaccine and autism, information about the dangers of the diseases it protected against, pictures and anecdotes — and concluded the following: “None of the interventions increased parental intent to vaccinate a future child. Refuting claims of an MMR/autism link successfully reduced misperceptions that vaccines cause autism but nonetheless decreased intent to vaccinate among parents who had the least favorable vaccine attitudes. In addition, images of sick children increased expressed belief in a vaccine/autism link and a dramatic narrative about an infant in danger increased self-reported belief in serious vaccine side effects.”

This is why getting people like McCarthy a platform in the first place is such a problem. You don’t need to get every listener to believe that vaccines are Actively Dangerous. You just need to create an atmosphere that suggests there is Room For Doubt and Debate. Then sit back and watch the vaccination rates drop.

Refuting her on Twitter is just preaching to the choir. I’m glad the choir is immune. But when it comes to immunity, that’s not enough.

Alexandra Petri writes the ComPost blog, offering a lighter take on the news and opinions of the day.