A vaccine may not even happen, and if it does could takes years.
https://www.cnn.com/2020/05/03/health/coronavirus-vaccine-never-developed-intl/index.html
"There are some viruses that we still do not have vaccines against," says Dr. David Nabarro, a professor of global health at Imperial College London. "We can't make an absolute assumption that a vaccine will appear at all, or if it does appear, whether it will pass all the tests of efficacy and safety.
Most experts remain confident that a Covid-19 vaccine will eventually be developed; in part because, unlike previous diseases like HIV and malaria, the coronavirus does not mutate rapidly.
But even if a vaccine is developed, bringing it to fruition in any of those timeframes would be a feat never achieved before. "We've never accelerated a vaccine in a year to 18 months."
In 1984, the US Secretary of Health and Human Services Margaret Heckler announced at a press conference in Washington, DC, that scientists had successfully identified the virus that later became known as HIV -- and predicted that a preventative vaccine would be ready for testing in two years.
Nearly four decades and 32 million deaths later, the world is still waiting for an HIV vaccine.
"An effective vaccine for dengue fever, which infects as many as 400,000 people a year according to the WHO, has eluded doctors for decades. In 2017, a large-scale effort to find one was suspended after it was found to worsen the symptoms of the disease."
Similarly, it's been very difficult to develop vaccines for the common rhinoviruses and adenoviruses -- which, like coronaviruses, can cause cold symptoms. There's just one vaccine to prevent two strains of adenovirus, and it's not commercially available.
"The lockdown is not sustainable economically, and possibly not politically," says Neal. "So we need other things to control it."
That means that, as countries start to creep out of their paralyses, experts would push governments to implement an awkward new way of living and interacting to buy the world time in the months, years or decades until Covid-19 can be eliminated by a vaccine.