Russia has surprised the world with President Vladimir Putin announcing the first COVID-19 vaccine to win approval, sparking debate among scientists over whether the country has bypassed necessary safety checks. The World Health Organisation is reportedly calling for caution, citing a possible lack of appropriate clinical trials.

The Russian breakthrough is one of more than 160 potential COVID-19 vaccines in various stages of trials around the globe.

At least 22 vaccines have entered phase one or two human trials, while another 139 are in preclinical stages, many on the brink of joining those currently ahead of the pack.

Three treatments developed in China, two in the US and one in the UK are in phase three human trials — the final hurdle which experts say is critical for ensuring public safety.

The Government has signed an agreement with UK-based drug company AstraZeneca to secure a potential COVID-19 vaccine developed by Oxford University, if its trials prove successful.

The science behind modern vaccination has evolved over hundreds of years. Put simply, it involves an intentional exposure to an inactive or weakened version of microbes that cause a disease to provoke the production of protective antibodies.

But developing safe and effective vaccines requires intensive and long-term endeavour, usually over a decade or so.

With the world focused on a fast-tracked treatment for the novel coronavirus, RMIT ABC Fact Check takes a look at the history of vaccine development in the fight against some of the world's most infectious diseases.