Summer is almost here. But your portfolio isn't on vacation. In fact, it's working to make you richer even as you sit by the pool. And as you sit by the pool, you may be wondering about a few biotech picks to add to your portfolio right now. Companies with potential positive catalysts on the horizon make good candidates.

Where can you find them? In the coronavirus space. Some of these stocks may have posted big gains already -- but the coronavirus is likely to be around for a long time, so companies working in the field still have much room for growth. Let's take a look at three biotech players making waves in potential prevention and treatment.

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Gritstone bio

Gritstone bio (GRTS -7.68%) is on the way to becoming a latecomer in the coronavirus vaccine market. But that's OK. The biotech company is working on a next-generation vaccine candidate that may work particularly well against variants. Today's vaccines target the coronavirus spike protein. That's the protein used to infect cells. But Gritstone's candidate targets the spike and other viral antigens. Targeting other antigens should offer broader protection in case the spike mutates extensively.

The biotech company began dosing participants in a phase 1 clinical trial in March. The company expects to report phase 1 data in the third quarter. So, again, a potential vaccine probably wouldn't be launched during the pandemic. Instead, this candidate -- if successful -- would reach commercialization farther down the road.

Gritstone also has other interesting work in the pipeline. The company is collaborating with Gilead Sciences (GILD -1.29%) on the development of a vaccine therapy for human immunodeficiency virus (HIV). This is part of Gilead's work to find a cure for the disease. The company also has six trials in oncology.

Gritstone shares are best for investors who can tolerate some risk. The company hasn't yet commercialized any products. But if Gritstone is successful with at least one of its projects in the coming years, the stock could soar.

RedHill Biopharma

A big catalyst may be just ahead for RedHill Biopharma (RDHL -1.97%). The company recently completed enrollment in the phase 2/3 trial of its investigational coronavirus treatment. RedHill is studying opaganib -- a drug delivered in pill form -- in 475 patients for the treatment of severe COVID-19.

So far, opaganib data are positive. Results from phase 2 in the U.S. back in December showed that opaganib reduced patients' needs for supplemental oxygen by day 14 of treatment. The potential treatment also has passed four independent safety-board reviews with flying colors.

Opaganib is expected to work against both the original novel coronavirus and its variants. That's because it doesn't target the virus itself. Instead, the drug candidate targets a protein within the body that helps the virus to replicate.

Meanwhile, RedHill is generating revenue from three gastroenterology products. In the first quarter, the company reported more than $20 million in revenue compared with $1.1 million in the year-ago period.

RedHill shares are down more than 10% this year. But Wall Street expects them to gain 185% in the coming 12 months. Now, with opaganib trial results ahead, may be a good time to get in on the story.

Vir Biotechnology

Vir Biotechnology (VIR -1.86%) recently transitioned from a clinical-stage company to a commercial-stage one. The U.S. Food and Drug Administration last month authorized the company's very first product for emergency use: an antibody treatment for COVID-19.

The FDA authorized the therapy for patients with mild-to-moderate COVID-19 who are at high risk of hospitalization. This puts Vir's antibody in the same playing field as that of Regeneron Pharmaceuticals (REGN -0.34%). The FDA authorized Regeneron's antibody cocktail late last year.

Vir's trial results show it reduced the risk of hospitalization or death by 85%. Regeneron showed a 70% reduction. And both treatments have shown efficacy against variants of concern. So it looks like Vir can carve out a spot next to its bigger rival.

The biotech company also has three hepatitis B candidates in phase 2 trials, and earlier-stage programs in influenza A and HIV.

Vir shares have climbed more than 60% so far this year. Wall Street forecasts the stock will double in the coming 12 months. That's possible.

But even if the stock doesn't grow that quickly, I'm optimistic about steady, long-term gains. This company is at the beginning of its growth story, so I expect the shares to head much higher over time.