KEY POINTS
  • President Donald Trump touted the news almost immediately in an all-caps tweet: "STOCK MARKET UP BIG, VACCINE COMING SOON."
  • President-elect Joe Biden urged Americans to keep up their efforts to prevent the spread of the virus.
Democratic President-elect Joe Biden delivering remarks on Covid-19 at The Queen theater on Oct. 23, 2020 in Wilmington, Delaware and U.S. President Donald Trump addressing supporters during a Make America Great Again rally in Gastonia, North Carolina, Oct. 21, 2020.

A major development in the quest for a coronavirus vaccine prompted starkly different reactions from President Donald Trump and President-elect Joe Biden, illustrating just how differently a Biden administration plans to approach the pandemic.

Pharma giant Pfizer and German biotech company BioNTech announced Monday that its leading vaccine candidate is more than 90% effective in preventing Covid-19 among those without evidence of prior infection.