Sifting through countless of stocks in the Pharmaceuticals industry can be tedious, and sometimes two stocks are just too similar to judge which is the better investment. If you’re on the fence about investing in Merck & Co., Inc. or Jazz Pharmaceuticals plc because you’re not sure how they measure up, it’s important to compare them on a few factors before making your decision.

Read on to learn how Merck & Co., Inc. and Jazz Pharmaceuticals plc compare based on key financial metrics to determine which better meets your investment needs.

About Merck & Co., Inc. and Jazz Pharmaceuticals plc

Merck & Co., Inc. operates as a healthcare company worldwide. It offers human health pharmaceutical for various areas under the Keytruda, Keytruda Qlex, Welireg, Gardasil, ProQuad, M-M-R II, Varivax, Vaxneuvance, Capvaxive, RotaTeq, Pneumovax 23, Bridion, Prevymis, Dificid, Zerbaxa, Winrevair, Adempas/ Verquvo, Ohtuvayre, Lagevrio, Isentress/Isentress HD, Delstrigo, Pifeltro, Belsomra, Januvia, and Janumet brands. The company also provides veterinary pharmaceuticals, vaccines and health management solutions and services, such as livestock products under the Nuflor, Bovilis/Vista, Bovilis Cryptium, Banamine, Estrumate, Matrix, Resflor, Zuprevo, Revalor, Safe-Guard, M+Pac, Porcilis, Circumvent, Nobilis/Innovax, Paracox and Coccivac, Exzolt, Slice, Imvixa, Clynav, Aquavac/Norvax, Aquaflor, Flexolt brands; Allflex Livestock Intelligence solutions; and companion animal products under the Bravecto One-Month, Bravecto Injectable/Quantum, Bravecto TriUNO, Bravecto Plus, Sentinel Spectrum, Sentinel Flavor Tabs, Numelvi, Optimmune, Nobivac NXT, GilvetMab, Otomax, Mometamax, Mometamax Ultra, Posatex, Caninsulin/Vetsulin, Panacur, Safeguard, Regumate, Prestige, Scalibor/Exspot, Sure Petcare, and Home Again brands. It has development and commercialization agreement for three of Daiichi Sankyo’s deruxtecan ADC candidates; AstraZeneca PLC to co-development and co-commercialize AstraZeneca’s Lynparza products for multiple cancer types; licensed to develop, manufacture and commercialize LM-299, a novel investigational PD-1/VEGF bispecific antibody from LaNova; and collaboration agreement with Eisai Co., Ltd., Bayer AG, and Ridgeback Biotherapeutics LP, as well Moderna, Inc. Merck & Co., Inc. has strategic collaboration with Infinimmune, Inc. to discover and develop antibodies against multiple therapeutic targets. The company was founded in 1891 and is headquartered in Rahway, New Jersey.

Jazz Pharmaceuticals plc identifies, develops, and commercializes pharmaceutical products in the United States, Europe, and internationally. The company offers Xywav to treat cataplexy or excessive daytime sleepiness (EDS) with narcolepsy and idiopathic hypersomnia (IH); Epidiolex for seizures associated with Lennox-Gastaut syndrome (LGS), Dravet syndrome (DS), or tuberous sclerosis complex (TSC); Rylaze for the treatment of acute lymphoblastic leukemia or lymphoblastic lymphoma; Enrylaze to treat acute lymphoblastic leukemia and lymphoblastic lymphoma; Zepzelca for the treatment of metastatic small cell lung cancer with disease progression on or after platinum-based chemotherapy; Ziihera to treat HER2-positive biliary tract cancers; Modeyso for the treatment of diffuse midline glioma harboring an H3 K27M mutation; and Defitelio to treat severe veno-occlusive disease. It also develops Zanidatamab in Phase 3 trial to treat HER2-positive gastroesophageal adenocarcinoma (GEA) and biliary tract cancers (BTC); Dordaviprone to treat H3 K27M-mutant diffuse glioma; and Vyxeos for the treatment of newly-diagnosed therapy-related acute myeloid leukemia. In addition, the company is developing Zanidatamab to treat neoadjuvant and adjuvant breast cancer; Vyxeos for the treatment of High-risk MDS, newly diagnosed untreated patients with high-risk AML, and De novo intermediate or adverse risk AML stratified by genomics; and JZP3507 to treat pheochromocytoma and paraganglioma that are in Phase 2 clinical trials. Further, it develops JZP815 to treat Raf and Ras mutant tumors; JZP898 for the IFN INDUKIN molecule in solid tumors; and JZP047 to treat absence epilepsy that are in Phase 1 clinical trials. The company collaboration agreements with Redx Pharma plc, Autifony Therapeutics Limited, Zymeworks Inc., Sumitomo Pharma Co., Ltd., Werewolf Therapeutics, Inc; and AbCellera Biologics Inc. Jazz Pharmaceuticals plc was founded in 2003 and is headquartered in Dublin, Ireland.

Latest Pharmaceuticals and Merck & Co., Inc., Jazz Pharmaceuticals plc Stock News

As of July 30, 2026, Merck & Co., Inc. had a $320.6 billion market capitalization, compared to the Pharmaceuticals median of $569.9 million. Merck & Co., Inc.’s stock is up 23.7% in 2026, down 0.7% in the previous five trading days and up 57.07% in the past year.

Currently, Merck & Co., Inc.’s price-earnings ratio is 36.3. Merck & Co., Inc.’s trailing 12-month revenue is $65.8 billion with a 13.6% net profit margin. Year-over-year quarterly sales growth most recently was 4.9%. Analysts expect adjusted earnings to reach $2.736 per share for the current fiscal year. Merck & Co., Inc. currently has a 2.6% dividend yield.

As of July 30, 2026, Jazz Pharmaceuticals plc had a $16.2 billion market cap, putting it in the 84th percentile of all stocks. Jazz Pharmaceuticals plc’s stock is up 48.7% in 2026, down 0.4% in the previous five trading days and up 121.6% in the past year.

Currently, Jazz Pharmaceuticals plc’s price-earnings ratio is 547.4. Jazz Pharmaceuticals plc’s trailing 12-month revenue is $4.4 billion with a 0.7% net profit margin. Year-over-year quarterly sales growth most recently was 19.1%. Analysts expect adjusted earnings to reach $25.309 per share for the current fiscal year. Jazz Pharmaceuticals plc does not currently pay a dividend.

How We Compare Merck & Co., Inc. and Jazz Pharmaceuticals plc Stock Grades

Stock evaluation requires access to huge amounts of data and the knowledge and time to sift through it all, make sense of financial ratios, read income statements and analyze recent stock movements. AAII created A+ Investor, a robust data suite that condenses data research in an actionable and customizable way suitable for investors of all knowledge levels, to help investors streamline and work through such data.

AAII’s proprietary stock grades come with A+ Investor. These offer intuitive A‐F grades for each of five key investing factors: value, growth, momentum, earnings estimate revisions and quality. Here, we’ll take a closer look at Merck & Co., Inc. and Jazz Pharmaceuticals plc’s stock grades to see how they measure up against one another.

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Merck & Co., Inc. and Jazz Pharmaceuticals plc Stock Value Grades

Company	Ticker	Value
Merck & Co., Inc.	MRK	D
Jazz Pharmaceuticals plc	JAZZ	D

Successful stock investing involves buying low and selling high, so stock valuation is an important consideration for stock selection.

Buying stocks that are going to go up typically means buying stocks that are undervalued in the first place, although momentum investors may argue that point.

AAII’s A+ Investor Value Grade derives from a stock’s value score. The Value Score is the percentile rank of the average of the percentile ranks of the price-to-sales ratio, price-earnings ratio, enterprise-value-to-EBITDA (EV/EBITDA) ratio, shareholder yield, price-to-book-value ratio and price-to-free-cash-flow ratio. The score is variable, meaning it can consider all six ratios or, should any of the six ratios not be valid, the remaining ratios that are valid. To be assigned a Value Score, stocks must have a valid (non-null) ratio and corresponding ranking for at least two of the six valuation ratios.

Stocks with a Value Score from 81 to 100 are considered deep value, those with a score between 61 and 80 are a good value and so on.

Merck & Co., Inc. has a Value Score of 27, which is Expensive. Jazz Pharmaceuticals plc has a Value Score of 34, which is Expensive.

The Value Stock Winner: No Clear Winner

Neither Merck & Co., Inc. or Jazz Pharmaceuticals plc has a high enough value grade to be considered a “winner.” Investors who are considering these companies should do additional due diligence and research to see if either could be a good addition to their portfolio. It’s important to look at a wide range of financial metrics in order to determine if Merck & Co., Inc. or Jazz Pharmaceuticals plc is the better investment when it comes to value.

Merck & Co., Inc. and Jazz Pharmaceuticals plc Growth Grades

Company	Ticker	Growth
Merck & Co., Inc.	MRK	A
Jazz Pharmaceuticals plc	JAZZ	A

The foundation of growth investing is seeking out stocks of companies exhibiting strong, consistent and prolonged growth that is expected to continue into the future.

In order to compute the growth score and assign it a letter grade, the percentile ranks for each of three components‐consistency of annual sales growth, five-year sales growth rankings adjusted for extreme levels, and consistency of positive annual cash from operations‐must be determined. These three rank figures are added together, and the sum is ranked against the entire stock universe to arrive at a company’s Growth Score to create an equal distribution of grades.

The companies in the bottom 20% of the stock universe receive Growth Grades of F, considered to be very weak, while those in the top 20% receive A grades, which are considered very strong.

Merck & Co., Inc. has a Growth Score of 100, which is Very Strong. Jazz Pharmaceuticals plc has a Growth Score of 89, which is Very Strong.

The Growth Grade Winner: It’s a Tie!

Looking at the Growth Grade breakdown above, both Merck & Co., Inc. and Jazz Pharmaceuticals plc have a grade of A. For investors who focus solely on a company’s upward growth, further research should be conducted into both companies’ other financial metrics before deciding whether to invest.

Merck & Co., Inc. and Jazz Pharmaceuticals plc’s Estimate Revisions Grades

Company	Ticker	Earnings Estimate
Merck & Co., Inc.	MRK	C
Jazz Pharmaceuticals plc	JAZZ	C

Earnings estimate revisions scores consider the magnitude of a company’s earnings surprise in its last two reported fiscal quarters. Often, positive surprises beget further positive surprises‐or at least continued sales growth (the exact opposite is generally true, too).

Estimate revisions offer an indication of what analysts are thinking about the short-term prospects of a firm. Estimate revisions are based on the statistical significance of a firm’s last two quarterly earnings surprises and the percentage change in its consensus estimate for the current fiscal year over the past month and past three months.

Merck & Co., Inc. has a Earnings Estimate Score of 42, which is Neutral. Jazz Pharmaceuticals plc has a Earnings Estimate Score of 52, which is Neutral.

The Earnings Estimate Revisions Stock Winner: No Clear Winner

Neither Merck & Co., Inc. or Jazz Pharmaceuticals plc has an Earnings Estimate Revisions Grade that could be considered a “winner.” Investors considering these companies should do additional due diligence and research to see if either could be a good addition to their portfolios. It’s important to look at a wide range of financial metrics in order to determine if Merck & Co., Inc. or Jazz Pharmaceuticals plc is the better investment when it comes to estimate revisions.

Other Merck & Co., Inc. and Jazz Pharmaceuticals plc Grades

In addition to Estimate Revisions, Value and Growth, A+ Investor also provides grades for Momentum and Quality.

Momentum grades help uncover stocks experiencing anomalously high rates of return; research finds that stocks with high relative levels of momentum tend to outperform, whereas those with low levels of momentum tend to continue underperforming.

AAII’s A+ Investor Quality Grade comes from the ranking of key metrics. Specifically, the quality grade is the percentile rank of the composite of return on assets (ROA), return on invested capital (ROIC), gross profit relative to assets, buyback yield, change in total liabilities to assets, accruals, Z double prime bankruptcy risk (Z) score and F-Score.

These 2 key factors, when combined with the above, provide a holistic view into a particular stock. Further, by joining A+ Investor you can see whether Merck & Co., Inc. and Jazz Pharmaceuticals plc pass any of our 60+ stock screens that have outperformed the market since their creation.

So, Which Is the Better Investment, Merck & Co., Inc. or Jazz Pharmaceuticals plc Stock?

Overall, Merck & Co., Inc. stock has a Value Score of 27, Growth Score of 100 and Estimate Revisions Score of 42.

Jazz Pharmaceuticals plc stock has a Value Score of 34, Growth Score of 89 and Estimate Revisions Score of 52.

Comparing Merck & Co., Inc. and Jazz Pharmaceuticals plc’s grades, scores and metrics can act as a solid basis to determine whether they may be a good investment or not. You’ll also want to look at your portfolio’s asset allocation as well as your risk tolerance and financial goals to see if either of these stocks would make a good fit for you. AAII can help you figure out which investments align with your individual needs and preferences.

Investors are encouraged to do their own due diligence and research. In this way, individuals can effectively become managers of their own assets‐without having to rely on others for financial independence. You can count on AAII for timeless articles on financial planning and stock-picking, unbiased research and actionable analysis.

A+ Investor adds to our qualitative teaching with a powerful data suite to help you whittle down investment choices to find stocks, exchange-traded funds (ETFs) or mutual funds that meet your needs.

AAII Disclaimer

We make no representations or warranties that any investor will, or is likely to, achieve profits similar to those shown, because past, hypothetical or simulated performance is not necessarily indicative of future results. Before making an investment decision, you should consider your circumstances and whether the information on our content is applicable to your situation. This information was prepared in good faith, and we accept no liability for any errors or omissions. The full disclaimer can be read here.