Coronavirus cases are on the rise in the U.S., and with the threat of more lockdowns looming, investing in stay-at-home stocks is one way to protect your portfolio in case there's another market crash this year. Businesses with products and services that are in demand even when consumers are stuck at home are in good shape to perform well, even amid the COVID-19 pandemic.

The following two companies look to be good investments during these adverse times, and investors should consider buying shares today. And if you invest in both, you'll be providing your portfolio with some great diversification.

1. SmileDirectClub

SmileDirectClub (NASDAQ:SDC) is a terrific example of a business that could do very well when people are at home. Its popular teeth-straightening products are a hit with consumers, because they're cheaper than braces. And because customers can get the products shipped directly to their homes without even needing to visit one of the company's SmileShops, SmileDirectClub makes for the ideal stay-at-home stock.

Woman in isolation during COVID-19.

Image source: Getty Images.

The Tennessee-based company is coming off a first quarter in which its sales were up a modest 11% year over year. However, the company estimates sales could have been up as much as 33% if not for the impact of COVID-19. SmileDirectClub closed its SmileShops (except for those in Hong Kong) due to the pandemic, which led to a decline in revenue. 

But according to its website, many of its locations around the world have since reopened and are now taking appointments. That, combined with many people losing their jobs during the pandemic -- and losing health coverage along the way -- could result in stronger demand for its cost-effective teeth-straightening products.

SmileDirectClub will release its second-quarter results Aug. 12.

2. Campbell Soup

Campbell Soup (NYSE:CPB) products are growing in popularity with consumers who are staying at home. People are stocking up on the bare essentials in case they aren't able or willing to make frequent trips to the grocery store. And the company's canned soups and other products are ideal options to put in the pantry and forget about until you need them weeks (or even months) later.

The New Jersey-based company released its third-quarter results June 3, with net sales up a remarkable 15% year over year. Those results were for the three-month period ending April 26., and they showed a big improvement over pre-pandemic days. In the previous quarter -- the results of which went through Jan. 26 -- Campbell's net sales were flat from the prior-year period.

The results are so promising that Campbell has raised its guidance for fiscal 2020. While many companies are withdrawing their forecasts for the year in light of the uncertainty relating to COVID-19, Campbell is optimistic, given the demand it's seeing for its products during the pandemic. The company was previously expecting to see flat net sales for 2020 (between negative 1% and positive 1%). Now, however, Campbell's is expecting to see positive growth for the year of at least 5.5%, and possibly as high as 6.5%.

Which stock is the better buy?

Both of these stocks are doing about as well as the S&P 500 this year:

SDC Chart

SDC data by YCharts

However, that could change in the quarters ahead, as strong demand could carry these stocks higher the remainder of this year.

If you're a conservative investor, Campbell's might be the better option for you, for a few reasons. Unlike SmileDirectClub, which has incurred a loss in each of the past three years, Campbell's is a safe bet to stay in the black, having had no trouble recording profits in any of its past 10 fiscal years.

In addition, Campbell's also pays a dividend that yields about 2.8%, which is better than the S&P 500 average of about 2%. SmileDirectClub currently doesn't offer its investors a dividend. And Campbell's stock also trades at less than 2 times sales, while SmileDirectClub is trading at more than 4 times its revenue.

But if you're a growth investor willing to take on some risk, the teledentistry stock may be the better long-term option. In fact, both of these stocks could be great options to add to your portfolio as people spend more time at home.