A vaccine recently created for monkeys offered equal protection against most COVID-19 variants, including Omicron—in addition to the original SARS virus from the early 2000s.

The vaccine, developed by researchers at the Scripps Research Institute in California, is protein-based like traditional flu vaccines, as opposed to mRNA-based COVID vaccines like those from Pfizer and Moderna. It was administered in a two-dose series to rhesus macaques—a type of “old world” monkey—in hopes of immunizing them against COVID-19, according to an article published earlier this month in Science Translational Medicine.

The results surprised researchers, who found that the vaccine was “equally effective” against most COVID variants of concern and, in some cases, “highly effective” against Omicron subvariants. It also provided protection against SARS, a coronavirus that appeared in China in 2002 before spreading to four other countries. SARS infected more than 8,000, killing about 10% and devastating regional economies.

The robust immune response of the rhesus monkeys is “fascinating,” Raiees Andrabi, an investigator in the institute’s department of immunology and microbiology, told Fortune. And it prompts the question of whether scientists can engineer a vaccine that elicits a similar response in humans.

The robust antibody response of the study’s monkeys stands in contrast to how first-generation COVID vaccines have protected humans. The original COVID vaccines typically don’t defend against Omicron subvariants until a first “booster” dose.

Even then, such protection is typically limited to severe disease and death. Those shortcomings have prompted Pfizer and Moderna to recently tweak their formulas in a bid to better protect against infection from now-dominant variants BA.4 and BA.5.

The results of the Scripps trial are great news for rhesus macaques, no doubt. The good news for humans is that the trial alerted scientists to a region on COVID-19’s spike protein that, if targeted by a vaccine, is more likely to lead to the takedown of all SARS viruses a vaccinated person encounters.

Creating a vaccine that works similarly in humans would be a challenge owing to relatively small but important genetic differences, “but this is not to say it’s impossible,” Andrabi said.

While Andrabi’s team awaits the results of related studies, it will continue to work on a pan-betacoronavirus vaccine that would provide protection against a broader family of coronaviruses. The family includes SARS; COVID-19; viruses like OC43 that typically cause common colds; and MERS, or Middle East Respiratory Syndrome, which was first identified in Saudi Arabia in 2012. MERS spread to nearly 30 countries, infecting about 2,500 and killing more than a third.