Stocks slump after new vaccines prove less effective for some COVID-19 variants

Stock markets dropped Friday after two pharmaceutical companies said their vaccines were somewhat less effective against the South African strain of COVID-19.

The Dow Jones Industrial Average dropped 620 points, or 2 percent, and the S&P 500 fell 73 points, or 1.9 percent, closing out the worst week for Wall Street since October.

Johnson & Johnson announced Friday morning that their single-shot vaccine was 66 percent effective, but less effective against the South African strain.

It did prove 100 percent effective in preventing hospitalization or death after a month, however.

Thursday night, Novavax released similar results from its vaccine, which it said was 90 percent effective against COVID-19, but only 60 percent effective against the South African strain in people without HIV.

The advent of two new effective vaccines could immensely speed up the vaccination campaign, but the caveat of lower effectiveness against the South African strain is raising concerns of a prolonged fight against COVID-19.

The drops closed out a tumultuous week of trading that has also been upended by retail traders homing in on a few stocks, such as GameStop, sending their valuations soaring and upending some traditional investors and hedge funds.

Updated at 4:09 points.