S&P 500 Gains and Losses Today: Pfizer and Merck Jump; Payments Stocks Decline

Group 1: Pfizer and Merck Developments - Pfizer shares increased by 6.8% after announcing a deal to sell medications at lower prices to Medicaid patients, alongside a three-year exemption from certain tariffs on pharmaceutical imports [3][6] - Merck shares also surged by 6.8% following a positive regulatory recommendation in Europe for a product aimed at preventing respiratory syncytial virus (RSV) in newborns and infants [4] Group 2: Market Reactions and Trends - Major U.S. equity indexes experienced slight gains on the last trading day of the third quarter, with the Dow gaining 0.2%, Nasdaq rising 0.3%, and S&P 500 adding 0.4% [2] - Stocks in the pharmaceutical industry, including Charles River Laboratories, Bio-Techne, and IQVIA Holdings, performed well, benefiting from the positive news surrounding Pfizer and Merck [4] Group 3: Impact on Financial Technology and Payments Sector - Shares of payment processors Paycom and Block fell over 4% after OpenAI announced a partnership with Stripe to integrate shopping features into ChatGPT, potentially disrupting the payments and e-commerce markets [8] - Credit card issuers, including Capital One Financial, saw shares decline close to 5% due to concerns over a potential government shutdown impacting consumer sentiment and transaction frequency [9]