Scientists and drug companies are racing to develop and test treatments and vaccines that address COVID-19, the disease caused by the novel coronavirus. Work on both is progressing at an unprecedented speed — but researchers are starting essentially from scratch on vaccine development, so the process is going to take a long time. Treatments, on the other hand, were further along when the outbreak started and might be available sooner.

“They’re in vastly different situations right now,” says Florian Krammer, a professor and vaccine development expert at the Icahn School of Medicine at Mount Sinai.

Both treatments and vaccines are important for a robust and effective response to the outbreak. Treatments help people after they already have a disease; in the case of COVID-19, researchers hope to treat the around 15 percent of COVID-19 patients who have non-mild symptoms. Vaccines, on the other hand, help prevent people from getting sick in the first place.

Scientists started work on drugs to treat coronaviruses during the SARS and MERS outbreaks, but because the outbreaks died down, the job was never completed. Now, they’re able to dust off that old research and start building on it. The leading candidate is a drug called remdesivir, which was developed by the pharmaceutical company Gilead. Research showed that it could block SARS and MERS in cells and in mice. In addition, remdesivir was used in a clinical trial looking for treatments for Ebola — and therefore, it had already gone through safety testing to make sure it doesn’t cause any harm.

That’s why teams in China and the US were able to start clinical trials testing remdesivir in COVID-19 patients so quickly. There should be data available showing if it helps them get better as soon as April. If it proves effective, Gilead would presumably be able to ramp up production and get the drug in the hands of doctors fairly quickly, Krammer says.

The vaccine development process will take much longer. Experts say that it will be between a year and 18 months, or maybe longer, before they’re available to the public. One of the strategies for creating a vaccine involves making copies of one part of the virus (in this case, the bit that the novel coronavirus uses to infiltrate cells). Then, the immune system of the person who receives the vaccine makes antibodies that neutralize that particular bit. If they were exposed to the virus, those antibodies would be able to stop the virus from functioning.

The pharmaceutical company Moderna is the furthest along in the process; it already has that type of vaccine ready for testing. A trial in 45 healthy people to make sure that it’s safe will start in March or April and will take around three months to complete. After that, it’ll have to be tested in an even larger group to check if it actually immunizes people against the novel coronavirus. That will take six to eight months. And then, it’ll have to be manufactured at a huge scale, which poses an additional challenge.

Making vaccines is always challenging. Developing this one is made more difficult because there has never been a vaccine for any type of coronavirus. “We don’t have a production platform, we have no experience in safety, we don’t know if there will be complications. We have to start from scratch, basically,” Krammer says.

It was much easier to make a vaccine for H1N1, known as swine flu, which emerged as a never-before-seen virus in 2009. “There are large vaccine producers in the US and globally for flu,” Krammer says. Manufacturers were able to stop making the vaccine against the seasonal flu and start making a vaccine for this new strain of flu. “They didn’t need clinical trials, they just had to make the vaccine and distribute it,” he says.

There won’t be a vaccine done in time to hold off any approaching outbreak of COVID-19 in the US or in other countries where it’s still not widespread. That’s why treatments are so important: along with good public health practices, they can help blunt the impact of the disease and make it less of an unstoppable threat. The best experts can hope for is that a vaccine can help prevent other outbreaks in the future if the novel coronavirus sticks around.