U.S. National Institutes of Health scientists played "a major role" in developing Moderna Inc's  COVID-19 vaccine and the agency intends to defend its claim as co-owner of patents on the shot, NIH Director Dr. Francis Collins told Reuters on Wednesday.

In a story first reported by the New York Times on Tuesday, Moderna excluded three NIH scientists as co-inventors of a central patent for the company's multibillion-dollar COVID-19 vaccine in its application filed in July.

Moderna expects 2021 sales of $15 billion to $18 billion from the COVID-19 vaccine - its first and only commercial product - and up to $22 billion next year.

In a statement emailed to Reuters, Moderna acknowledged that scientists at NIH's National Institute of Allergy and Infectious Diseases (NIAID) played a "substantial role" in developing Moderna's messenger RNA (mRNA) vaccine, but the company said it disagrees with the agency's patent claims.

Collins said the NIH has been trying to resolve the patent conflict with Moderna amicably for some time and has failed.

NIH has asserted that three of its scientists - Dr. John Mascola, Dr. Barney Graham and Dr. Kizzmekia Corbett - helped design the genetic sequence used in Moderna's vaccine and should be named on the patent application.