Investing in companies that provide indispensable products or services to customers is a proven way to grow richer over time. And few, if any, items are more important than the medicines and vaccines that pharmaceutical companies sell to the world.

Medicines and vaccines have been and will continue to be crucial to improving both patients' quality and duration of life. Here are a couple of pharmaceutical stocks that are compelling buys for investors seeking a mix of income and growth prospects.

A pharmacist serves a customer.

Image source: Getty Images.

1. Merck

Merck & Co.'s (MRK 0.10%) $263 billion market capitalization makes it the fifth-biggest pharmaceutical company in the world. The company's crown-jewel cancer drug, Keytruda, accounted for just over a third of its $45.5 billion in year-to-date sales.

Keytruda undoubtedly plays a significant role in the company's growth story. But don't make the mistake of thinking of Merck as a one-trick pony. The New Jersey-based drugmaker has numerous other products that are set to generate at least $1 billion in net sales in 2022. The most prominent ones include its human papilloma virus (HPV) vaccine, Gardasil; the COVID-19 antiviral medicine Lagevrio; and two diabetes medicines, Januvia and Janumet.

Merck expects this portfolio of dozens of products, along with its animal health segment, to generate net sales of around $59 billion in 2022. And looking toward the end of this decade, when the patent for Keytruda expires in 2028, the company should have the pipeline necessary to replace its lost revenue.

That's because Merck has 115 projects in numerous therapeutic areas, such as infectious diseases, vaccines, and "respiratory and immunology," which are either in clinical development or under review by regulatory agencies. This explains why analysts are projecting 11.1% annual earnings growth over the next five years -- much higher than the drug manufacturing industry's average growth forecast of 6.5%.

Merck combines tremendous growth prospects with a 2.8% dividend yield, which is solid compared to the S&P 500 index's 1.6% yield. And with the dividend payout ratio positioned to come in under 40% in 2022, the passive income that Merck provides to shareholders has nowhere to go but up.

The icing on the cake that makes the stock a buy for income investors is its valuation. Merck's forward price-to-earnings (P/E) ratio of 13.6 is below the S&P 500 pharmaceutical average multiple of 14.4.

2. Novartis

Novartis' (NVS 1.10%) $201 billion market cap positions it as the sixth-largest pharmaceutical company overall and the biggest among international companies. Novartis is a diversified drugmaker, boasting a portfolio of 14 products on pace to log at least $1 billion in 2022 sales.

The Swiss company's blockbuster medicines are in a variety of therapy areas, including immunology, cardiovascular, and neuroscience. Novartis' top-selling drug, the immunology megablockbuster Cosentyx, made up just 9.8% of the company's $37.9 billion in year-to-date net sales.

Given that it's planning to spin off its consumer health business, Sandoz, Novartis will be even more focused on bolstering its drug pipeline, currently 149 projects deep. This is why analysts are anticipating 3.6% annual earnings growth for the next five years.

Along with its 4% dividend yield, Novartis should have little difficulty delivering annual total returns in the high single digits. And with the forward dividend payout ratio projected to be about 53%, income investors can feel assured that this high dividend is here to stay.

Best of all, shares of the stock can be picked up at a forward P/E ratio of 13.8. This represents a slight discount against the S&P 500 pharmaceutical average, which makes Novartis a high-yielding buy.