What happened

Shares of Shake Shack (NYSE:SHAK), Restaurant Brands International (NYSE:QSR), and McDonald's (NYSE:MCD) popped over 22%, 11%, and 5%, respectively, early Monday morning after the markets absorbed news from Pfizer that its leading drug candidate was having major success against COVID-19.

So what

Pfizer announced that its leading vaccine candidate was found to be more than 90% effective in preventing COVID-19 in trial participants who had no prior infection. The study had just over 43,000 participants, and Pfizer reported no serious safety concerns. Pfizer will now submit for Emergency Use Authorization (EUA) to the U.S. Food and Drug Administration after the next required safety milestone is achieved. That's anticipated to happen in the third week of November.

"Today is a great day for science and humanity," Albert Bourla, Pfizer chairman and CEO, said in a press release Monday. "The first set of results from our Phase 3 COVID-19 vaccine trial provides the initial evidence of our vaccine's ability to prevent COVID-19. We are reaching this critical milestone in our vaccine development program at a time when the world needs it most with infection rates setting new records, hospitals nearing over-capacity and economies struggling to reopen."

SHAK Chart

SHAK data by YCharts

Now what

Today's announcement from Pfizer gave life to many industries and stocks that had been crippled by COVID-19 and social distancing measures. Stocks of movie chains, brick-and-mortar retailers and department stores, and restaurants all moved higher today on hopes that we're now seeing beginning of the end of the coronavirus pandemic.

Many fast food stocks have fared better than dine-in stocks as their drive-thru business remained largely unchanged, and the adoption of delivery apps also helped mitigate negative COVID-19 impacts. McDonald's, for instance, managed to post a 4.6% increase in comparable sales in the U.S. during the third quarter driven by what it calls the "3 Ds": digital, delivery, and drive thru. While global comparable sales declined 2.2% during the third quarter, management noted sequential monthly improvements for all segments throughout the quarter.

Cheeseburger and fries

Image source: Getty Images.

Restaurant Brands, the owner and operator of Burger King, Popeyes, and Tim Hortons, has lagged the S&P 500 since COVID-19 swept the nation, likely because the company's financials have proven less resilient than competitors such as McDonald's. In fact, Restaurant Brands' systemwide sales growth during the third quarter declined 5.4% despite Popeyes posting an impressive 21.5% increase. Despite slightly lagging McDonald's comparable sales, the company managed to generate a solid third quarter with sequential improvements in cash flow, and has been able to reopen roughly 96% of its restaurants as of September.

Shake Shack was hit hard but has made consistent enough improvements that investors are hopping back on board. Total company-operated restaurant sales declined 17% during the third quarter, which was far better sequentially compared to the second quarter's 39% decline. Furthermore, the company only posted a 5% decline in fiscal October. Same-Shack sales (say that three times fast) have sequentially improved for six straight months. Now that the company has stabilized sales, it can resume its look toward growth: The company plans to open between 35 and 40 new company operated stores in 2021.

Ultimately, the vaccine news from Pfizer will be a boost for beaten down stocks in many crippled industries. Many restaurant and fast food stocks will rise today, but investors would be wise to realize we're not out of this pandemic just yet. Make sure to invest in companies with solid balance sheets that have proven capable of offsetting some, or all, negative COVID-19 impacts.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.