The stock market's recent volatility shouldn't concern investors with a long-term outlook. In fact, it's probably a blessing in disguise for the buy-and-hold crowd. Several great stocks, after all, are now trading at attractive valuations. 

In the beaten-up healthcare sector, for instance, AbbVie (ABBV 1.26%) and Amgen (AMGN -0.71%) stand out as two outstanding buys following their poor showing through the first nine months of 2019. Here's why these top dividend-paying biotech stocks are worth adding to your portfolio right now.

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AbbVie: Buy the fear

AbbVie's shares are shrouded in fear right now. The singular reason is that the company's main revenue source -- the anti-inflammatory drug Humira -- has firmly entered the back end of its rather remarkable run as one of the industry's most profitable products.

Emphasizing this point, Humira's sales appear to have crested at around $20 billion in 2018, with biosimilars taking a heavy toll in Europe this year. Some Wall Street analysts have even floated the idea that Humira's sales might plummet by an eye-popping 85% from their former high-water mark by 2025. That's obviously not a favorable trend line, but it's also not the end of the world. 

AbbVie has built out a solid portfolio of next-generation products and it recently inked a merger agreement with Allergan (AGN) that will immediately soften the blow from Humira's demise. Underscoring this point, AbbVie should have no fewer than six blockbuster products (Botox, Imbruvica, Orilissa, Rinvoq, Skyrizi, and Venclexta) by 2025, thanks to its top-notch clinical pipeline and tie-up with Allergan.  

Apart from AbbVie's impressive portfolio of newer growth products, there are two more compelling reasons to consider buying this elite biotech stock soon. First, AbbVie's shares are dirt cheap right now at 7.56 times forward earnings. Second, this Dividend Aristocrat sports a substantial yield of 5.84% at current levels. Bargain-hunters, in kind, should probably take advantage of AbbVie's yearlong downturn. This top drugmaker will eventually rebound after all. 

Amgen: Better days are ahead

Amgen's shares have fallen by nearly 3% so far this year. As a result, the stock is now trading at 12 times forward earnings, which is a lower-tier valuation for a blue chip biotech -- especially one that sports a slightly above-average dividend yield of 3%. Still, the market appears more than content to simply sit on the sidelines when it comes to this top dividend stock, despite its attractive valuation and juicy dividend.

What's keeping investors at bay? Amgen is going through a radical makeover right now, and the final product remains a work in progress, to put it mildly. The brief rundown is that newer growth products like the migraine treatment Aimovig and cholesterol-lowering drug Repatha haven't been able to fully offset the declines emanating from the biotech's portfolio of aging superstars. Amgen's top line, in fact, is forecast to dip by 3.9% in 2019. 

Another area of concern is the biotech's oncology portfolio. Some of the company's most important early-stage cancer assets simply haven't lived up to expectations in the clinic. These setbacks have weighed on Amgen's shares this year, which makes sense given their importance to the biotech's long-term value proposition.

Still, there are two solid reasons to consider buying this blue chip biotech stock right now. First up, Amgen's recent acquisition of the anti-inflammatory medicine Otezla is expected to immediately boost earnings and quarterly sales. The company should, in fact, return to top-line growth by next year. Second, Amgen has one of the largest cash positions within the entire space. So there's a good chance that the biotech will pursue more bolt-on acquisitions in order to accelerate its return to form. 

The bottom line is that Amgen definitely has the pieces in place to move past these various headwinds. Now, this turnaround may not materialize overnight, but it will almost certainly happen. As such, patient investors may want to dig into this story before the market starts to change its tune.