It's a good day for companies reporting earnings, and strong quarters are powering the Dow Jones Industrial Average (DJINDICES:^DJI) higher. The Dow has rocketed to yet another 52-week high, continuing to surge through the start of 2013. As of 2:20 p.m. EST, the index has pulled in gains of 70 points, or 0.51%. Let's check out the biggest names making moves today.

A healthy dose of optimism
It's a great day to be a health care investor, and Pfizer (NYSE:PFE) is leading the charge on the Dow. Along with several other companies, Pfizer reported earnings that smashed expectations. The company's profit almost quadrupled from a year ago, buoyed by its sale of its nutrition business to Nestle. Despite the patent loss of best-selling blockbuster Lipitor last year, Pfizer's earnings, even without the Nestle sale, slightly topped analyst projections. And despite the hit to Lipitor sales, revenue also beat the Street's best guess.

So far, Pfizer's shares have risen more than 3.2% to hit a new 52-week high.

The optimism around the medical industry has pushed Merck (NYSE:MRK) higher as well, even though the company doesn't report its quarterly data until later in the week. Merck is among the leaders of the Dow, up 1.5% so far today. The company is dealing with its own patent-loss blues, as declining sales of Singulair have weighed on growth expectations. Merck investors could use a good report; the stock has lost nearly 6% over the past three months.

Johnson & Johnson (NYSE:JNJ) and Unitedhealth Group have also swung up on the day, with shares gaining a little more than 1% each. J&J recently reported earnings that beat expectations, but its 2013 guidance disappointed Wall Street. The company is debating selling or spinning off its diagnostics business in its search for new growth. The guidance hit hasn't stopped this stock from hitting a new 52-week high as well, however.

Even outside the health care field, stocks on the Dow lean heavily toward winners. However, Hewlett-Packard (NYSE:HPQ) is leading the small corps of laggards down today, with shares falling 3.9%. Reports have surfaced from a PDF file on the company's website that HP may be preparing to launch its own version of Google's Chromebook, a laptop operating on Google's Chrome OS. However, with the PC market under fire, it'll take a lot more than that to turn this beleaguered company around.

Fool contributor Dan Carroll has no position in any stocks mentioned. The Motley Fool recommends Johnson & Johnson. The Motley Fool owns shares of Johnson & Johnson. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.