Rite Aid (NYSE:RAD) shares were up more than 9% around 2 p.m. today after the company announced that same-store sales for December grew 2.9% year over year. This keeps the company's string of positive monthly same-store sales results intact following a 2.1% improvement in October compared to the year-ago period and a 2.8% jump in November. 

Rite Aid's stock initially rose following its fiscal 2014 third-quarter earnings announcement on Dec. 23, based on improvements in both non-GAAP revenue and net income. But until today's same-store-sales announcement, Rite Aid's share price had experienced a steady decline, based primarily on tempered expectations for the coming year.

But at roughly $5.50 a share around 2 p.m., a roughly 9% improvement from this morning's opening bell, investors are clearly pleased with Rite Aid's string of positive same-store sales results. Through the 43-week period ending Dec. 28, 2013, same-store sales are up a more modest 0.5%, according to Rite Aid's statement.

December's pharmacy sales, despite the negative impact of introducing new generic drugs, once again led the way, jumping 4.1% year over year. November and October same-store sales were also led by pharmacy results, improving 3.9% and 3.4% compared to the previous year, respectively.

Same-store sales measures compare results from stores open at least a year. Stores open less than a year are not included in a same-store-sales calculations.