Moderna Inc on Thursday said it believes countries around the globe would continue buying its COVID-19 vaccine for years even if patents on the shots are waived, noting that rivals would face significant hurdles in scaling up manufacturing.

The comments come a day after the United States said it would support waiving intellectual property rights for COVID-19 vaccines in order to help speed an end to the pandemic, paving the way for what could be months of negotiations to hammer out a specific waiver plan. 

Moderna shares were off 7.5% after falling as much as nearly 12% earlier. Shares of other COVID-19 vaccine manufacturers like Pfizer Inc were also down on the patent news.

"While this is a negative headline," said Morgan Stanley analysts in a research note, there is no mechanism "to force management to teach other manufacturers how to make their vaccine, suggesting no change to the status quo."

Moderna, which said in October it would not enforce patents on its vaccine during the pandemic, noted the lack of companies able to rapidly scale up complex manufacturing of a similar vaccine to meet surging global demand.

"They will have to go run a clinical trial, get the data, get the product approved and scale manufacturing. This does not happen in 6 or 12 or 18 months," Moderna Chief Executive Stephane Bancel said on a post-earnings conference call.

Moderna has faced its own hurdles scaling up production with some shortfalls in the manufacturing supply chain, which includes Swiss contract manufacturer Lonza Group, leading to delivery delays in Europe.

Bancel said he has had to tell some countries, "we're very sorry. We have no more supply for you in 2021."

Still, the company said it expects to produce between 800 million to 1 billion doses this year.

Moderna raised its 2021 sales forecast for its COVID-19 shot by 4.3% to $19.2 billion on Thursday, two days after Pfizer increased its full-year COVID-19 vaccine sales forecast more than 70% to $26 billion. 

Moderna expects vaccine output could increase to 3 billion doses in 2022 to meet demand from nations looking to stock up supplies and sign up deals for "booster" doses.

Early clinical trial data released on Wednesday showed that a third dose of either Moderna's current shot or an experimental new vaccine increases immunity against the more easily transmissible virus variants first found in Brazil and South Africa.

Moderna, which is seeking to expand authorization of its vaccine to children and adolescents, on Thursday said an initial analysis of a study in those aged 12 to 17 showed an efficacy rate of 96%.

The company also reported its first-ever quarterly profit on sales of the vaccine.

(Reporting by Manas Mishra in Bengaluru and Carl O'Donnell in New York; Editing by Arun Koyyur and Bill Berkrot) ((Manas.Mishra@thomsonreuters.com; www.twitter.com/Manasmishra24; within U.S. +1 646 223 8780, outside U.S. +91 806749 2709;))