What happened

E-commerce stocks got hit hard on Monday as the market reacted to a game-changing development in the race for a COVID-19 vaccine.

As of 2:30 p.m. EST, shares of Amazon.com (NASDAQ:AMZN), Square (NYSE:SQ), PayPal (NASDAQ:PYPL), and Shopify (NYSE:SHOP) were down 3.3%, 6.1%, 7.1%, and 10.5%, respectively.

So what

Online retail and digital payments have been some of the best-performing stocks of 2020, as investors have sought out shelter from the COVID storm. E-commerce businesses -- many of which have seen their sales soar during the coronavirus pandemic -- have provided a welcome refuge. Prior to today, shares of Amazon, PayPal, Shopify, and Square had surged 79%, 87%, 163%, and 217%, respectively, since the end of 2019. 

A keyboard button labeled sell.

Investors sold off shares of e-commerce companies on Monday. Image source: Getty Images.

However, after Pfizer and BioNTech's blockbuster announcement on Monday that clinical trial results suggest their coronavirus vaccine candidate, BNT162b, could be more than 90% effective at preventing COVID-19, many investors apparently decided to take profits in e-commerce stocks.

Now what

After incredible advances this year, it's understandable that some people would want to lock in some gains. But it's important to note that the migration of retail sales to online channels -- and with it, the shift from cash to digital transactions -- will not come to a halt after the COVID-19 crisis subsides. These are powerful long-term trends that should continue to propel the growth of Amazon, Square, PayPal, and Shopify for many years to come. Investors, therefore, would likely be best served by holding on to the stocks of these e-commerce leaders.

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.