Calculating vaccines’ impact

“Vaccine vindication” (SN: 1/25/14, p. 5) stated that vaccines have prevented 103 million cases of childhood diseases such as polio and rubella in the United States since 1924.

“How can the study assume there were so many cases of illness that were prevented?” asked Carolyn Bredenberg in an e-mail. “Were the data extrapolated from old data, or inferred from models based on old data, or what?”

Researchers looked at disease rates during prevaccine times and the increase in the U.S. population since then to estimate the number of illnesses that vaccines have prevented, explains departments editor Erika Engelhaupt. “The number of prevented cases is the difference between expected cases and actual cases,” she says. “Vaccines may actually have prevented even more illnesses than this calculation reveals, since the number of prevaccine cases may have been underreported.”

Cat-induced death toll revised

Last year, Susan Milius reported new estimates of the number of wild animals killed by domestic cats in the United States (“Cats claim billions of bird and small mammal victims annually,” SN: 2/23/13, p. 14).

In December 2013, the authors of the original article in Nature Communications adjusted their estimates of the wildlife killed by cats each year. The first version of the paper included a narrower range of values than was appropriate for the statistical confidence level given. Fixing this error did not alter the basic conclusions of the paper, but the death tolls did change, with the originally published range of 1.4 billion to 3.7 billion cat-killed birds widening to 1.3 billion to 4.0 billion. The 6.9 billion to 20.7 billion range of small mammals killed by cats became 6.3 billion to 22.3 billion. The Science News article has been updated online.

Taming wildcat genetics

Feline domestication may have begun in the Far East with the small wildcat species Felis silvestris, as Susan Milius reported in “Earliest farm cats found in China” (SN: 1/25/14, p. 8).

Online commenter Mark S. wanted to know how similar the wildcats are to their domesticated cousins. “Cats go feral very easily,” he wrote. “Can F. silvestris be socialized if you start with a young kitten, or is there a real genetic difference?”

Milius can’t say whether wildcat kittens might act like domestic cats with the right training, but “the genetic differences are modest enough for plenty of researchers to treat domestic cats as just another subspecies of F. silvestris. Those slight differences may be important, though. Conservationists worry that any remnants of truly wild subspecies populations are losing distinctive adaptations through frequent crossbreeding with domestics, which include ‘feral’ cats.”

New life for The Science Life

Science Visualized premiered on the back page of Science News in October, taking the place previously occupied by The Science Life, which featured profiles of scientists and science enthusiasts.

The Science Life “was a nice snapshot of a working scientist — something a younger person (and older!) could connect to,” Karey Kluesner e-mailed. “I know you also have a student website, but I strongly feel that giving science a face on a regular basis is a very important thing versus simply having another page with pictures. The Science Life much better meets the goal of visualizing science — it makes it more real and gives credit to all the people working in the background to make everyone’s life better and more meaningful.”

Erika Engelhaupt responds: “Thank you to readers who have shown support for The Science Life. We have not abandoned the effort to cover the people and stories behind the science: The Science Life will be revived as an occasional feature in the Notebook section, partly in response to reader feedback.”

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