The Dow Jones Industrial Average was last seen down 443 points, breaking down past both its June closing low and the psychologically significant 30,000 level.

Biotech stocks moved back and forth amid some volatility before finishing the week ending Feb. 11 modestly lower, reversing the gains from the previous week. Earnings news flow continued to dominate proceedings.

The FDA and CDC announced their recommendation to pause the use of Johnson & Johnson's JNJ COVID-19 vaccine following incidences of severe clots. J&J's pain turned into  gains for other COVID-19 vaccine companies.

Biopharma stocks, which started the week on a firm footing, lost momentum mid-way through amid market-wide sell-off triggered by waning stimulus hopes.

Biotech stocks made a steady recovery over the week ended October 2, although Friday's weakness trimmed some of the gains of the week. Companies working on anti-COVID-19 antibody treatments were in the news during the week.