What happened

Shares of e-commerce companies are falling today after Pfizer and BioNTech announced that their coronavirus vaccine candidate has demonstrated 90% effectiveness in preventing participants from contracting COVID-19. Here's how these prominent e-commerce stocks are trading as of 2 p.m. EST:

So what

The coronavirus pandemic has driven a broad surge in engagement for e-commerce platforms throughout the year as consumers shifted purchasing patterns away from brick-and-mortar stores toward online alternatives. The prospect of an effective vaccine may reduce or reverse that trend if people are able to go back to safely shopping in physical retail stores. Sea, JD.com, and MercadoLibre operate major e-commerce platforms in Southeast Asia, China, and Latin America, respectively.

Shopping cart, delivery van, globe, and credit card icons on keyboard keys

Image source: Getty Images.

Sea has two primary segments: digital entertainment and e-commerce. The digital entertainment segment, which publishes mobile games, has also enjoyed a surge in engagement as people need entertainment while staying home -- quarterly active users jumped 61% last quarter. Gross orders in the e-commerce business soared by 151% and gross merchandise value (GMV) skyrocketed by 110% in the second quarter.

While an effective vaccine could hypothetically put a dent in those growth rates, management noted on the last earnings call that certain markets that successfully combated the virus like Taiwan still saw "heightened" growth that was stronger than pre-COVID-19 levels. Sea will report third-quarter results on Nov. 17.

JD.com posted a 34% jump in revenue in the second quarter, with annual active customer accounts increasing to 417.4 million. China was able to contain the virus through aggressive lockdown measures earlier this year. The drastic restrictions have already allowed many people to return to relative normalcy in the Middle Kingdom, so the availability of a vaccine may not significantly impact JD.com's current trajectory. "Given the COVID-19 situations, now largely stabilized in China, we kind of go back to our original business plan for the second half," CFO Sandy Xu said in August.

MercadoLibre reported third-quarter results last week, and they showed unique active users increasing by a strong 92% to 76.1 million. On a constant currency basis, GMV soared by 117% and total payment volume (TPV) processed through the company's Mercado Pago payment platform jumped by 161%. CFO Pedro Arnt attributed some of MercadoLibre's operating leverage to "the growth in organic demand brought about by the effects of the COVID-19 pandemic on consumer behavior."

Now what

Pfizer and BioNTech are still conducting clinical trials of the vaccine candidate and currently believe they may be able to produce 50 million doses this year before ramping production to 1.3 billion doses in 2021. The companies plan to submit for Emergency Use Authorization from the U.S. Food and Drug Administration within a few weeks. While progress on a vaccine is great news, it may not be widely available until the third quarter of 2021.

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.