By Dhirendra Tripathi

Investing.com – Stocks of Covid vaccine-makers continued to be weighed down Wednesday by the promise shown by Merck’s (NYSE:) antiviral oral medicine against the dreaded infection.

Merck’s Friday announcement that trials of a drug it is developing against Covid showed that it could halve the risks of hospitalization and deaths was a blow for the shares of Novavax (NASDAQ:), BioNTech (NASDAQ:), Pfizer (NYSE:) Moderna (NASDAQ:) and Johnson & Johnson (NYSE:).

If approved, molnupiravir, the antiviral drug, could be the world’s first oral medicine for Covid, the company said in a note. Merck will seek an emergency authorization for the U.S. in as quick as possible.

Novavax, Moderna and BioNTech traded 3.3% to 4.3% lower in today’s session. Johnson & Johnson fell 0.6%. Pfizer fell 0.8%, after BioNTech and Pfizer jointly created a vaccine.

Novavax lost about 30% since Thursday’s close of trading, one day prior to the Merck announcement. Moderna has 18% and BioNTech has 13%.

Pfizer and Johnson & Johnson, the two companies who are not very dependent on revenue from sales of the Covid shots, have fallen 2.7% and 2%, respectively. Merck announced the news just as Pfizer began to distribute its booster dose, which is for people over 65.

Novavax, the sole company yet to release its vaccine is among the others. Moderna has experienced some negative developments that have increased the stock’s volatility.

According to reports, Swedish public health agency has paused use of Moderna’s Covid vaccine for people born 1991 and later because of indications of heightened risk of side effects. People under 18 years old have been advised that Moderna shot has been stopped in Denmark.