By Lewis Krauskopf

NEW YORK (Reuters), Vaccine makers are benefiting from the emergence of a troubling coronavirus strain. Moderna (NASDAQ:) Inc., BioNTech Pfizer (NYSE:) Investors look for winners in uncertain markets.

Moderna shares have increased 28% in the week since Omicron was announced. The shares of Pfizer’s vaccine partner BioNtech also increased over the same time. Pfizer was up 6%, while BioNtech gained 15% in America. This contrasts with a decrease in 2.5%.

Moderna and BioNTech, the most widely used vaccines in America are Pfizer/BioNTech and Moderna. It is possible that they can re-engineer products to deal with the new variant.

“They are clear COVID plays and anything that ramps up the intensity of COVID is going to benefit them,” said Kevin Kedra, pharmaceuticals analyst at GAMCO Investors. “They are the front line of defense against COVID.”

The market reaction to this new version included a decline in leisure and travel stocks as well as a brief increase in stay-at home stocks. These stocks thrived in lockdowns that took place in 2020.

Companies have already made huge profits with their vaccines this year, which has helped to boost their stock prices. Moderna shares have risen 240%, Pfizer shares, which is also seeking emergency authorization to its antiviral COVID-19 experimental treatment, has risen 47% and BioNTech shares have risen by 340%.

Buying vaccine stocks forms part of a “playbook” that has been developed in the 18-months, giving or taking. I think it is more mechanical than thoughtful,” said Les Funtleyder, a healthcare portfolio manager at E Squared Capital.

“We don’t have all the information. Funtleyder stated that people are making rash decisions. While they may have made the right decision for themselves, we won’t know until a bit later.

Omicron is still a mystery. It’s contagious, it can cause severe diseases, and there are no vaccines to protect it.

The head of Moderna, Stéphane Bancel, said vaccines are unlikely to be as effective against Omicron as they have been against previous variants, while BioNTech’s chief said the company’s vaccine would likely offer strong protection against any severe disease from the new variant.

Kedra suggested that Bancel’s comments might have been one reason why shares of Moderna & BioNTech fell on Tuesday. Moderna fell 5%, while BioNTech dropped 3%.

Pfizer shares increased 3.5% Tuesday.

Analysts were scrambling to evaluate the implications of the new model for their businesses.

“It seems much more likely that we are going to have at least one more round of boosters,” said Daina Graybosch, senior research analyst at SVB Leerink.

Michael Yee, a Jefferies analyst (NYSE:), stated in a note that Omicron “represents an increase in the need for continued protection contre COVID-19 or its variants through primary vaccination for some and boosters for others.”

Omicron and the reverberation of its emergence has also affected shares of COVID-19-treatment makers. Vir Biotechnology (NASDAQ) has had its stock increase by around 45% in the past week, claiming that its antibody treatment will continue to be effective against this variant.

Adagio Therapeutics shares have surged by 130% during volatile trading. It stated that its experimental therapy against Omicron will continue to be effective.

Regeneron Pharmaceuticals (NASDAQ:) stated Tuesday that its Omicron-resistant antibody could prove less effective. They were also continuing to study the genetic variant and assessing the impact. Regeneron shares dropped 1% after Omicron was discovered.