Billionaire investor Hamish Douglass says the one-in-50-year pre-Christmas rally in global sharemarkets suggests too many investors are oblivious to the scientific reality of the coronavirus pandemic and are motivated by a dangerous "fear of missing out".

The Magellan chief investment officer, arguably Australia's most successful investor, said that although the positive developments of the Pfizer-BioNTech coronavirus vaccine and pending exit of US President Donald Trump from office had been a "nirvana outcome" for markets, investors should remain cautious.