What just happened? News that a Covid-19 vaccine being developed by Pfizer and its partner BioNTech has proved 90 percent effective at preventing the virus is being welcomed by the world. The reveal has given stock markets a huge boost, but companies that benefitted from the pandemic have seen their shares plummet.

Both Pfizer and BioNTech announced that their mRNA-based vaccine had been shown to be effective at blocking the virus in 90 percent of participants in stage 3 of its clinical trial, which included 43,358 participants. The vaccine uses a two-dose process, and Pfizer says, "no serious safety concerns have been observed." The company believes it can produce 50 million doses by the end of this year and up to 1.3 billion doses through 2021.

As per CNBC, to give you an idea of the importance of that 90 percent efficacy rate, scientists had been hoping for a vaccine that would be at least 75 percent effective. White House coronavirus advisor Dr. Anthony Fauci, meanwhile, had said 50 - 60 percent would be acceptable.

"I think we can see light at the end of the tunnel," said Pfizer Chairman and CEO Dr. Albert Bourla on CNBC's "Squawk Box."

While Covid-19 has decimated industries such as aviation, theaters, and many non-grocery firms, stay-at-home orders have improved several companies' bottom lines. With a potential vaccine on the horizon, the tables have turned: airlines, automotive, and cruise shares are just some of those on the rise, while video-conferencing service Zoom is down 13 percent, online-exercise giant Peloton is also down 13 percent, Etsy and Wayfair have dropped by double-digits, and even Amazon has fallen, by around 3 percent, the same as Shopify.

There's still a long way to go, and there's the question of how many people will be willing to take the vaccine, but it's nice to hear some positive Covid-related news.

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