Pfizer's significant beat on both earnings per share and sales estimates is likely to positively impact investor sentiment in the short term, despite the year-over-year decrease in sales. The substantial outperformance compared to analyst expectations suggests operational efficiency and strong demand for Pfizer's products, which could lead to upward pressure on the stock price. However, the decline in sales year-over-year might temper some of the positive momentum, making it crucial to monitor how the market interprets these mixed signals.