Billionaire investor Warren Buffett, through his company Berkshire Hathaway, has disclosed big bets on several pharmaceutical stocks.

Buffett's bets on the U.S. health care sector could potentially pay off as the pandemic continues.

Berkshire Hathaway disclosed its investments in a filing with the U.S. Securities and Exchange Commission submitted after the closing bell Monday. The company said it purchased new shares in pharmaceutical companies that included Bristol-Myers Squibb, AbbVie, Pfizer and Merck during the third quarter.

The amount the company paid for the shares was not disclosed but some of the stocks it purchased have seen price rises in value in recent weeks. Pfizer's stock price rose following its announcement that its vaccine candidate had proven to be over 90% effective in treating the disease. The price fell after Moderna announced its own vaccine progress.

Pfizer's stock closed at $37.33 per share Monday, Bristol-Myers Squibb at $64.50 per share, AbbVie at $98.36 per share, and Merck at $80.18 per share.

Berkshire Hathaway said it had also purchased new shares in wireless telecommunications provider T-Mobile. It said it had sold some of its stake in retail company Costco. The exact amounts were not specified.

The company acquired a substantial stake in mining company Barrick Gold in August. Buffett has repeatedly stated his stance on investing in gold - not worth investing in.

Buffett surprised when he made a large investment in the initial public offering of cloud computing company Snowflake.

Since the start of the year, Berkshire Hathaway has been slowly decreasing its positions in banks such as Goldman Sachs and Wells Fargo. It also offloaded entire stakes in four airlines - American, Southwest, United and Delta.