Pfizer Inc could have a COVID-19 vaccine available in the world's largest economy by the end of 2020.
Top tech brands drifted lower, as investors fretted over uncertainty around the COVID-19 pandemic.
The tech-heavy Nasdaq ended its two-day losing streak, as deal activity lifted sentiment on the sector.
The first time since March, both indexes had a drop for the fourth time in five days.
The market enables price discovery, and prices are based on interplay of supply and demand.
The plunge marked the biggest one-day drops for all three indexes since June.
Investors and stock traders continue to increase their buying pressures on technology and health stocks.
The massive price increase in recent weeks has lured many speculators into profit-taking.
