The study, published in the journal JAMA Otolaryngology-Head and Neck Surgery, estimated that between 7,00,000 and 1.6 million people in the US who had Covid-19 have lost or had a change in their sense of smell that has lasted for more than six months.
According to the researchers from Washington University School of Medicine in St. Louis, this is likely an underestimate, reports CNN.
The study suggests most people recover their sense of smell eventually, but some may never regain it.
The authors consider this a concern because, by comparison, prior to the pandemic, only 13.3 million adults age 40 and older had what scientists call olfactory dysfunction (OD) or chronic olfactory dysfunction (COD).
"These data suggest an emerging public health concern of OD and the urgent need for research that focuses on treating Covid-19 COD," the study said.
A study last year found that 72 per cent of people with Covid-19 recovered their sense of smell after a month, but for some, it is a much slower process.