(Bloomberg) -- Moderna Inc.’s market value has swelled by almost $24 billion this year on optimism that the biotech’s experimental messenger-RNA vaccine will play a part in tamping down the coronavirus pandemic.

The company is expected to have an interim early look this month at how effective its shot, mRNA-1273, is at preventing Covid-19. Results on Monday from Pfizer Inc. and BioNTech SE’s vaccine offered both boon and bane to Moderna. The shot set a high bar as a first look at their late-stage study showed more than 90% effectiveness is preventing symptomatic infections. At the same time, vaccine similarities bode well for Moderna.

Investors should expect more stock swings for Moderna, which has surged more than 280% this year. Options indicate shares could move 15% in either direction by the end of November and 26% if looking further out to Dec. 24.

Stay-at-home daytraders bolster many Covid-19 plays and -- for Gilead Sciences Inc. at least -- were quick to step aside once a commercial reality approached. Gilead’s stock peeled off more than 20% since a May 1 clearance for its Covid-19 treatment. Moderna is one of the biggest biotech short plays this year with over $1.93 billions shares shorted, according to S3 Partners data.

While Pfizer and Moderna are leading the pack, there are at least 11 late-stage studies underway including large-scale trials from AstraZeneca Plc and Johnson & Johnson.

“Given the competitive nature of Covid-19 vaccines (there could be many) and the uncertain duration of pandemic, we believe that the market is already ascribing a substantial amount of value to these vaccines, leaving us cautious on the ultimate opportunity,” JPMorgan analyst Cory Kasimov cautioned clients in a research note after Pfizer and BioNTech results.

Infection Triggers

For Moderna’s shot, an interim analysis will be triggered after 53 volunteers from its roughly 40,000-person study come down with a Covid-19 infection. The participants are split between those vaccinated and those getting a placebo, and volunteers will be followed for a safety analysis. A second analysis will occur after 106 infections. That might not take long with new infections accelerating and hitting a record in the U.S.

Pfizer’s shot is expected to have a required two months of safety data next week, which -- if all turns out well -- could get some high-risk individuals vaccinated in December, according to Anthony Fauci, the nation’s top infectious disease expert.

While the U.S. has signed Pfizer up for 100 million doses and an option for another 500 million, the country will need more than one vaccine to head off the Covid tide. And Moderna, back in August, signed a 100 million dose deal with the government.

Monday’s data from Pfizer grabbed the market’s attention, fueling a stock market rally that faded after investors began to contemplate the distribution logistics and how many vaccine-skeptical Americans will actually take it. And there is yet to be a full picture on safety or how long shots will be effective.

Each vaccine will also likely face its own Food and Drug Administration panel and initial shots are likely to be only available to higher-risk populations.

©2020 Bloomberg L.P.