Last year, Zika stunned public health officials when it was discovered that the virus, which otherwise evoked mild or no symptoms, caused devastating birth defects in babies born to women who became infected during pregnancy.

With the U.S. mosquito season ahead, scientists and medical officials are once again preparing to protect Americans from infection, and while a vaccine hasn’t yet hit the public, testing is set to begin on people. Research led by the National Institutes of Health, the government’s agency that funds medical research, will continue to determine whether the vaccines are safe and effective at protecting people from the virus.