The COVID-19 crisis has crushed many stocks over the past year, but it also lit a fire under stay-at-home stocks that benefited from social distancing measures and the growing usage of online services. But over the past month, Pfizer and Moderna revealed two vaccines that were more than 90% effective at preventing COVID-19.

Neither vaccine has been approved by the Food and Drug Administration (FDA) yet, but the headlines caused many investors to scurry out of stay-at-home stocks and toward battered sectors like travel and retail in hopes of capitalizing on a post-pandemic recovery.

Investors shouldn't blindly follow that herd, but they should recognize the companies whose stocks could crumble if the vaccines are approved. Let's look at three such stocks that stand to lose if a vaccine if fully approved.

Vials of a COVID-19 vaccine with surgical masks.

Image source: Getty Images.

1. Peloton Interactive

When Peloton (NASDAQ:PTON) went public last September, the exercise bike maker was widely ridiculed. Its bike cost $1,895 and required a $13 per month subscription to unlock most of its workout features. Analysts balked at its business model and widening losses, and its stock dropped from its IPO price of $29 a share to less than $20 this March.

However, Peloton's stock subsequently soared to over $110 a share as sales of its bikes surged throughout the pandemic. In fiscal 2020, which ended on June 30, its revenue doubled to $1.83 billion, its number of subscribers grew 113% to 1.09 million, and its net loss narrowed from $196 million to $72 million.

In the first quarter of 2021, its revenue rose another 232% year over year to $758 million, its subscriptions soared 137% to 1.33 million, and it posted a net profit of $69 million -- compared to a loss of $50 million a year earlier. For the full year, Peloton expects its revenue to rise at least 113%, its subscriber base to roughly double, and its adjusted EBITDA to grow more than 155%.

Those growth rates are jaw-dropping, but a lot of growth is already baked into its stock at nearly 280 times forward earnings. It's also hard to see Peloton maintain its current growth rates after the pandemic ends and gyms reopen. Current Peloton owners might stick with their current subscriptions, but the company will likely struggle to sell more bikes in a post-pandemic world.

2. Blue Apron

Meal kit maker Blue Apron (NYSE:APRN) has been struggling with decelerating growth, ugly losses, and a growing list of competitors since its IPO three years ago. But last year, the company started a painful turnaround process under its new CEO Linda Kozlowski, who previously served as Etsy's chief operating officer.

A Blue Apron meal kit.

Image source: Getty Images.

Instead of trying to win back lost customers, Kozlowski focused on stabilizing Blue Apron's losses and boosting its orders and revenue per existing customer. Those efforts, amplified by a pandemic-related shift toward online orders, enabled its revenue to rise again over the past two quarters.

Blue Apron's revenue still dipped 4% year over year to $345 million in the first nine months of 2020, but its net loss narrowed from $39 million to $34 million. It expect its revenue to decline less than 1% for the full year, compared to a 32% decline in 2019.

Next year, analysts expect Blue Apron's revenue to rise 5% with a narrower loss. That forecast indicates the company is reaching an inflection point, but the bears will point out that Blue Apron's biggest rival, HelloFresh (ETR:HFG), is growing at a much faster clip and expects its revenue to double this year.

If Blue Apron could barely squeeze out fresh growth during the pandemic, which was arguably an optimal market for meal kit deliveries, it could fare much worse after the crisis ends.

3. Zoom Video Communications

The pandemic turned Zoom (NASDAQ:ZM) into a household name that became synonymous with video calls over the past year. In fiscal 2020, which ended in January, Zoom's revenue rose 88% to $623 million as its adjusted earnings surged 483%.

But in the first half of fiscal 2021, Zoom's revenue soared 270% year over year to $992 million as more people used its platform for remote work, online education, and staying in touch with family and friends. Its adjusted earnings also surged tenfold.

Zoom expects its revenue to rise 281%-284% for the full year, and for its adjusted earnings to jump sevenfold. Those breakneck growth rates caused Zoom's stock to soar nearly 550% this year, and it now trades at 135 times forward earnings.

Zoom's stock might look cheap to investors who expect the pandemic to continue throughout the first half of 2021. But analysts expect Zoom's revenue and earnings to rise 30% and 15%, respectively, in fiscal 2022 -- which indicates its growth will decelerate as more people return to work and school. It could also struggle against aggressive competitors like Cisco's Webex and Facebook's Messenger Rooms.

At this point, it's impossible to tell if Zoom's growth will stabilize or fall off a cliff. But one thing seems certain: A successful vaccine could cause a lot of investors to take profits in this high-flying stay-at-home stock.

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.