The vaccine development timeline

The development of vaccines can take years. This is especially true when the vaccines involve new technologies that haven't been tested for safety or adapted to allow for mass production.

Why does it take so long? First, a vaccine is tested in animals to see if it works and if it's safe. This testing must follow strict lab guidelines and generally takes three to six months. The manufacturing of vaccines also must follow quality and safety practices.

Next comes testing in humans. Small phase I clinical trials evaluate the safety of the vaccine in humans. During phase II, the formulation and doses of the vaccine are established to prove the vaccine's effectiveness. Finally, during phase III, the safety and efficacy of a vaccine need to be demonstrated in a larger group of people.

Because of the seriousness of the COVID-19 pandemic, vaccine regulators might fast-track some of these steps. But it's unlikely that a COVID-19 vaccine will become available sooner than six months after clinical trials start. Realistically, a vaccine will take 12 to 18 months or longer to develop and test in human clinical trials. And we don't know yet whether an effective vaccine is possible for this virus.

If a vaccine is approved, it will take time to produce, distribute and administer to the global population. Because people have no immunity to the COVID-19 virus, it's likely that two vaccinations will be needed, three to four weeks apart. People would likely start to achieve immunity to the COVID-19 virus one to two weeks after the second vaccination.

A lot of work remains. Still, the number of pharmaceutical companies, governments and other agencies working on a COVID-19 vaccine is cause for hope.