NEW YORK CITY — A homegrown coronavirus variant from New York City is "gaining" across the boroughs and gives cause for concern, Dr. Anthony Fauci said.

Early research into the recently discovered variant — dubbed B.1.526 — shows signs it could evade monoclonal antibody treatments for COVID-19 and, to a certain extent, vaccine-induced antibodies, said Fauci, the director of the National Institute of Allergy and Infectious Diseases.

"So it's something we take very, very seriously," Fauci said during a Monday briefing at the White House.

Fauci's words added to what two early studies already found — the variant is present in up to 25 percent of coronavirus samples and shows signs it could make COVID-19 treatments and vaccines less effective.

But his words didn't come with the reassurance Mayor Bill de Blasio and his top health advisers offered when news about the variant broke last week.

De Blasio said New Yorkers shouldn't assume the worst until more research is done.

Fauci, for his part, wasn't all doom and gloom. He mostly reiterated the research and said more study is needed.

But he did note that the variant could have originated in an immunocompromised person.

"What I think is important — because we often get asked the question that's a reasonable question: Should people who are immunocompromised get vaccinated?" he said.

"And the answer is, 'Absolutely, yes.' Absolutely, yes. Because that's not only important for them for their own health, but that could be the breeding ground of the emergence of variants for the simple reason that, if you don't clear the virus rapidly, you're going to have immunological selection within a given individual."