Let's face it. Social Security doesn't provide enough income to live comfortably for many retirees. And bonds don't generate the returns that they did for previous generations. What can you do?

One good idea is to invest in high-yield dividend stocks that have solid long-term prospects. Brookfield Infrastructure Partners (NYSE:BIP), Pfizer (NYSE:PFE), and Welltower (NYSE:HCN) check off both boxes. Here's why these three dividend stocks should provide a nice supplement to your Social Security income.

Senior couple looking at laptop

Image source: Getty Images.

Brookfield Infrastructure Partners

There's plenty to like about Brookfield Infrastructure Partners. The company owns utilities, transport, energy, and communications infrastructure businesses in North and South America, Europe, and Asia Pacific. These businesses generate consistent cash flow, enjoy competitive moats, and tend to increase in value over time.

Brookfield's dividend currently yields 4.31%. The company has increased its dividend steadily in recent years. It should be in good shape to continue paying and hiking its dividend thanks to solid growth in its funds from operation (FFO) per share.

The future looks good for Brookfield also -- and not just because of the assets the company owns now. CEO Sam Pollock likes to wait for the right investment opportunities that can deliver the company's target return goal of 12% to 15%. Brookfield is also creative in how it makes deals for acquisitions, giving it an edge over other prospective buyers. Finally, the company is smart about when to sell assets that aren't performing as well to get the best price.

There is something to consider before buying Brookfield stock, however. It is a master limited partnership (MLP). That means your distributions could be taxed at your marginal tax rate rather than the lower long-term capital gains tax rate. 

Pfizer

Pfizer ranks as one of the best big pharma dividend stocks, with a dividend yield of 3.86%. The drugmaker's solid cash flow should keep those dividend checks flowing for a long time to come.

Although Pfizer's earnings growth was weak over the past few years, that should soon change. Sales for cancer drug Ibrance totaled $2.1 billion in 2016. Analysts think annual sales for the drug could more than double within a few years. Several drugs picked up through acquisitions should be huge winners for Pfizer as well, especially prostate cancer drug Xtandi and atopic dermatitis drug Eucrisa.

Pfizer also claims a pipeline chock-full of strong candidates. The company has 34 late-stage programs, notably including nine clinical studies for Bavencio. The drug won approval for its first indication, treating Merkel cell carcinoma, in March. 

Another part of Pfizer's business could also generate significant growth in the future. The company's essential health segment includes biosimilars, anti-infectives, and sterile injectables -- all of which are growing businesses. Although sales for legacy drugs that have lost patent exclusivity drag overall revenue down somewhat, this should be a lesser impact for Pfizer in the next few years.

Welltower

Welltower is another great dividend stock in the healthcare industry. Unlike Pfizer, though, the company isn't a drugmaker. Instead, Welltower is the largest healthcare-focused real estate investment trust (REIT) in the world. As a REIT, Welltower is required by law to distribute at least 90% of its income as dividends. Welltower's dividend currently yields 4.86%.

Thanks to its steadily increasing FFO, Welltower has been able to hike its dividend each of the last seven years. The company should be in pretty good shape to continue dividend increases in the future, especially after some portfolio adjustments made in 2016.

Welltower owns interests in senior housing and post-acute communities as well as outpatient medical properties. In the fourth quarter of last year, the company began repositioning its property portfolio to reduce its exposure to long-term and post-acute care (LTPAC) and increase its focus on premium private-pay healthcare real estate properties. That's a smart move, since private-pay business tends to be more predictable and more profitable than government-funded programs.

Over two-thirds of Welltower's portfolio consists of senior-living properties. This is an attractive area because of the growing senior population in the U.S. The target market for Welltower is expected to nearly double in the next three decades.

Keith Speights owns shares of Pfizer. The Motley Fool recommends Brookfield Infrastructure Partners and Welltower. The Motley Fool has a disclosure policy.