The Zika virus has swiftly spread worldwide, causing thousands of cases of the severe birth defect microcephaly and possibly many other developmental problems. In response, researchers in the U.S. and beyond have sped up study into vaccines and drugs to treat the virus, and have finally seen some encouraging results.

On Monday, the National Institutes of Health (NIH) announced the launch of the first of five clinical trials in humans to test the safety and effectiveness of a Zika vaccine. Four other trials in humans are launching in the upcoming months, and the vaccine has already shown promising results in animals. “We urgently need a safe and effective vaccine to protect people from Zika virus infection as the virus continues to spread,” said Dr. Anthony S. Fauci, director of the National Institute of Allergy and Infectious Diseases (NIAID) in a statement announcing the study.

In a separate just-published study in the journal Nature, another team of scientists identified a human antibody that prevents the fetus from becoming infected with Zika in pregnant mice. The antibody also prevented damage to the placenta and prevented adult mice from getting Zika infections. This research was in mice, so it can’t directly translate to humans, but it does suggest that a vaccine against Zika could spur protective antibodies that not only prevent people from getting the virus, but could protect a pregnant woman’s fetus. “No one has yet shown definitive protection in pregnancy,” says study author Dr. Michael Diamond, professor of medicine at Washington University School of Medicine. “This was suspected, but had not been demonstrated.”

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When the infection rates of most epidemics wane, so does public interest; it can be hard for scientists and pharmaceutical companies to complete work on vaccines and drugs. During the recent Ebola outbreak, government groups and companies rapidly developed vaccines for the virus that infected 28,000 people and killed 11,000. But by the time they were ready to test the vaccines in humans, there were too few infections and low levels of concern.

Dr. Moncef Slaoui of GlaxoSmithKline recently told a panel at Fortune’s Brainstorm Health conference in San Diego that the company has undergone significant financial loss over their Ebola vaccine development. Cases of Ebola in Liberia subsided before testing could start, and public attention turned to Zika, he said. “We were left with enormous expenses, huge responsibility of having a vaccine that was half baked, and nobody caring. That’s been a very difficult experience for us.”

But that’s not the case with Zika. Because it spreads by mosquitoes, experts believe the virus will be circulating for longer. “Ebola is [a virus] that basically you have it in an area, and then it gets extinguished,” says Diamond.

Public health experts are seeing more viruses spread by mosquitoes emerging in the Americas. Dengue, a virus spread by the same mosquitoes that transmit Zika, infects an estimated 400 million people every year. “We are seeing an unprecedented uptick in vector borne diseases and we are not sure why,” says Dr. Peter Hotez, dean for the National School of Tropical Medicine at Baylor College of Medicine (who was not involved in the recent studies). “We are still trying to get our arms around this.”

Diamond thinks Zika infections will continue for some time, though the number of cases may fluctuate. “My suspicion is that this will not be gone next year or the year after,” he says. The hope is a vaccine or drug will be available to protect people, especially pregnant women, from infection.

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