Two new peer-reviewed studies published in Science on Wednesday have scientists feeling optimistic about coronavirus antibodies providing both natural and vaccine-induced immunity against future infections, The Boston Globe reports.

The research teams led by Dr. Dan Barouch, head of Beth Israel’s Center for Virology and Vaccine Research, found rhesus macaque monkeys were immune to the coronavirus after being re-injected with the live virus following recovery from their initial infection. And a separate study found two doses of one of six DNA vaccine prototypes — ones that use the genetic code for portions of a protein the coronavirus likely uses to invade cells — also provided protection.

DNA vaccines reportedly aren’t in development for human testing, and scientists are reportedly skeptical of their efficacy, but that’s why some are excited about the results of the study. The fact that DNA vaccines worked on the monkeys and in some cases developed antibodies at levels comparable to those produced by the response to the live virus “really tell you this is doable,” said Dr. Michael Nelson, director of the Center for Infectious Diseases Research at the Walter Reed Army Institute of Research.

Barouch was cautious about the results, noting that more research needs to be done in humans. Rhesus macaques, which are frequent test subjects in global coronavirus research, are about as close as scientists can get to humans in terms of genetic makeup, but they’re still a different species. And the jury is still out on how long immunity might last. Still, Barouch believes the findings are a cause for optimism. “Our team found this data very compelling,” he said.