Pfizer Inc. (PFE) is a biopharmaceutical company, multinational developer, and manufacturer of health care products. The publicly-traded company owns several household brands — including Advil, Centrum, Lipitor, Lyrica, Prevnar, and Viagra — and manages a portfolio of health products. Pfizer released Q3 2018 earnings on October 30, 2018. The pharmaceutical company reported $13.3 billion in revenues for the quarter, about flat compared to $13.2 billion over the same period last year. 

Not surprisingly, the largest investors of Pfizer are mutual funds. Here are the company's four largest institutional shareholders as of October 29, 2018.

Vanguard Total Stock Market Index Fund (VTSMX)

The Vanguard Total Stock Market Index was launched in April 1992. Since then, the fund's assets have grown to $756.6 billion, and it invests primarily in U.S. large and giant cap stocks. With 148.9 million shares of Pfizer as of October 2018, VTSMX is the company's largest mutual fund holder. The fund has invested 0.86% of its portfolio into Pfizer and owns about 2.54% of the company. The Vanguard Total Stock Market Index Fund has a 10.57% three-year annualized return and a minimum investment of $3,000.

Vanguard 500 Index Fund (VFINX)

The Vanguard 500 Index Fund Investor Shares seeks to provide investment results corresponding to the price and yield performance of the S&P 500 Index, its benchmark index, with a high degree of positive correlation. VFINX was issued by Vanguard in August 1976 and has assets of $459.3 billion, 1.05% of which are invested in Pfizer. With 109.2 million shares, about 1.86% of the company, the fund is Pfizer's second-largest institutional shareholder as of October 2018. The Vanguard 500 Index Fund has a 10.79% three-year annualized return and a minimum investment of $3,000.

SPDR S&P 500 ETF (SPY)

The SPDR S&P 500 ETF (SPY) is the first ETF to be introduced in the U.S. public market and remains one of the most popular to this day. The fund holds 66.6 million shares of Pfizer, which translates to 1.14% of the company and a third-place ranking among the company's top institutional investors as of October 2018. SPY invests 1.05% of its $250.43 billion portfolio in Pfizer. The SPDR S&P 500 ETF has a twelve-month yield of 1.73%.

Vanguard Institutional Index Fund (VINIX)

The Vanguard Institutional Index Fund Institutional Shares (VINIX) is an institutional fund that tracks the S&P 500 Index. The fund follows a passively managed, full replication approach invested in 508 stocks. With 55.9 million shares of Pzier in its portfolio, VINIX is the company's fourth-largest institutional shareholder. As of October 2018, the fund invests 1.05% of its 235.2 billion portfolio in its 0.95% ownership of Pfizer. The Vanguard Institutional Index Fund has a 10.79% three-year annualized return and a minimum investment of $3,000.