Today, a highly controversial study in which researchers synthesized a smallpox relative from scratch is finally seeing the light of day. The paper, in PLOS ONE, spells out how virologist David Evans at the University of Alberta in Canada, and his research associate Ryan Noyce ordered bits of horsepox DNA from the internet, painstakingly assembled them, then showed that the resulting virus was able to infect cells and reproduce.

The study stirred alarm when Science first reported it in July 2017 because it might give would-be terrorists a recipe to construct smallpox virus, a major human scourge vanquished in 1980. And now that it’s out, many scientists say the paper doesn’t answer the most pressing question: Why did they do it?

The team claims its work, funded by Tonix, a pharmaceutical company headquartered in New York City, could lead to a safer, more effective vaccine against smallpox. But safe smallpox vaccines already exist, and there appears to be no market for a horsepox-based replacement, says virologist Stephan Becker of the University of Marburg in Germany. “It simply does not add up,” Becker says. Given the apparent lack of benefits, publishing the paper was “a serious mistake,” says Thomas Inglesby, director of the Center for Health Security at the Johns Hopkins University Bloomberg School of Public Health in Baltimore, Maryland. “The world is now more vulnerable to smallpox.”