The upshot was that Democrats were 50 percent more likely to say that they would get the life-saving vaccinations, according to a study published in the peer-reviewed Journal of Health Politics, Policy and Law. Matthew A. Baum, the Harvard scholar who wrote the journal article, told me that he couldn’t calculate how many of the total flu deaths were attributable to conservatives putting too much faith in their pundits.

Something similar may have happened when conservatives like Michele Bachmann denounced the HPV vaccine, which protects against cervical cancer (Bachmann suggested that the vaccine could be “very dangerous”). Only 35 percent of girls have received the full course of HPV vaccinations, with particularly low rates in more conservative states like Arkansas, Mississippi, Utah and Kansas. That can’t be good for women in those states.

Of course, the left has long had its own version of this problem as well. After Richard Nixon’s 1972 landslide re-election, Pauline Kael of The New Yorker famously said she was mystified because she knew only one person who had voted for Nixon. MSNBC and The Huffington Post have become cocoons for liberals, just as Fox News is for conservatives.

Both Fox News and MSNBC rely more on punditry than on reporting from the field, and I remember once early in the Iraq war when I was with American troops watching on Fox News Channel as blowhards in the studio claimed that Iraqis were welcoming us with flowers. We watched, stunned, wondering what war the network was covering.

Research suggests that the echo chamber effect is disproportionately a problem on the right, leading inhabitants to perceive a warped reality. Many Republicans were shocked that Mitt Romney was defeated last fall because they had been assured that he would win. And a Pew survey last year found that the proportion of conservative Republicans who believe Obama is a Muslim has doubled since 2008 to 34 percent.

Then there was the time Glenn Beck aired the theory that Obama is the anti-Christ (he later said he had been joking).