There are close to 9 million confirmed COVID-19 cases in the U.S. and there could be many more to come as some experts say that the country is already in a third wave of the coronavirus pandemic. And with no light at the end of the tunnel, there's even more of a reason for investors to consider adding coronavirus stocks -- investments that will do well amid the pandemic -- to their portfolios. 

Two of the better stocks you can add right now include Quest Diagnostics (NYSE:DGX) and Snap (NYSE:SNAP). They're both coming off some strong performances in October and they are likely going to remain great buys for the foreseeable future. Here's why.

1. Quest Diagnostics

One of the recurring themes you hear over and over when it comes to the pandemic is the need for testing. In order to protect people and to keep the economy running, there needs to be testing on an ongoing basis. That way, people who know they are infected can stay home and prevent the spread of COVID-19. And that's why demand for Quest's testing services isn't likely to run low anytime soon.

Woman in isolation during covid-19.

Image source: Getty Images.

On Oct. 22, the New Jersey-based company released its third-quarter results for the period ending Sept. 30, where sales of $2.79 billion were up 42% year over year and ahead of analyst expectations of $2.72 billion. Net income of $568 million was also more than double the prior-year period's profits which totaled $215 million. Adjusted earnings per share (EPS) of $4.31 were well ahead of the $3.72-per-share earnings that Wall Street was looking for.

CEO Steve Rusckowski credited the impressive performance during the period to "continued demand for COVID-19 testing and the rapid recovery of healthcare utilization," stating that the 22 million molecular and serology tests it's conducted thus far related to the pandemic is more than anyone else. The company also noted the healthcare system was showing signs things were returning back to normal with Quest's "base testing volume" continuing to recover in Q3. With COVID-19 cases on the rise, that may not be the case for much longer. But Quest can do well in either event because if there's a surge in coronavirus cases, demand for COVID-19 tests will increase.

The healthcare stock's a good buy whether you're looking for a coronavirus stock to hold or just a stable investment to hold. Year to date, shares of Quest are up over 15%, soundly outperforming the S&P 500 and its 2% gains over the same period.

2. Snap

Snap is a top-notch stay-at-home stock as Snapchat is a great boredom-buster for people with nowhere to go. Like Quest, Snap's also doing well amid the pandemic with more users on its platform than before.

The California-based company released its third-quarter numbers on Oct. 20 for the period ending Sept. 30 and Snap posted record quarterly revenue of $679 million, up 52% year over year. Wall Street was only expecting sales of $549.99 million for the period. Its adjusted EPS was a positive $0.01, which was also better than the $0.04 loss that analysts were expecting.

One of Snap's key metrics is daily active users, and at 249 million, that was an 18% improvement from the same period last year. User interaction was also up, with the company reporting a 25% year-over-year increase in the number of daily "snaps" users were making during the period (on average).

Snap's also giving users even more reason to continue using its app, with the opportunity to create their own augmented reality experiences through its Lens Studio. In addition, it's partnered with several companies that will allow consumers to have "virtual try-on experiences" with their products, utilizing augmented reality.

There's plenty that can keep Snap users engaged and using its app, which is why the stock continues to look like a good investment during the coronavirus pandemic. Year to date, the stock is up more than 150%, getting a big boost from its recent results. 

Which one is the better coronavirus stock today?

Snap investors have enjoyed some great returns in 2020, but the stock may be too expensive for new investors today. At a price-to-sales multiple of around 28, it's far more expensive than Quest is today, which is trading at just two times its revenue. Although there's a lot of excitement of late surrounding the tech company's recent earnings report, investors are paying a much larger premium than the 15 times revenue they were valuing the stock at a year ago. 

The safer buy today is definitely Quest. Although investors aren't as bullish on the stock this year, its lower valuation makes it less likely to face a correction should the market crash. And with COVID-19 testing numbers likely to climb in future quarters, the stock could be an underrated buy right now.

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.