Loss of taste and smell during Covid may mean better immunity from reinfection

Losing your sense of taste and smell is one of the more disconcerting symptoms of Covid. But it could have its benefits. See how.

Losing your sense of taste and smell during a Covid infection may mean you are more likely to develop higher antibody levels that could protect you from reinfection for months, a new study has found.

A team of researchers from Columbia University in the US tested the blood of more than 300 people who had Covid-19 between April and June, 2020.

Just over 60% of these participants reported altered taste and smell during their infection, and the researchers found those people were more likely to have had strong levels of Covid antibodies in their blood following their illness.

The results of the observational study were published last week in the journal PLOS One.

“As the coronavirus disease 2019 (Covid-19) pandemic unfolded, chemosensory dysfunction, or impairment of smell and/or taste, was identified as a key symptom of severe acute respiratory syndrome coronavirus (SARS-CoV-2) infection,” the authors wrote.

“Recent meta-analyses report that olfactory loss is present in 43% to 62% of Covid-19 patients, though this estimate may vary based on ethnicity, age, disease severity, and method of chemosensory evaluation. In addition to its high prevalence, olfactory loss typically presents early in the course of the disease, making it a useful sentinel symptom to prompt further testing or management.”

Many people with Covid lose their sense of smell and taste.

About 20% of patients with Covid may have no symptoms other than a diminished sense of smell, the researchers said.

Temporary loss of smell with viral infections is thought to be related to inflammatory changes in the nasal cavity that prevent smells from reaching the olfactory epithelium. However, recent evidence suggests that Covid infection impairs smell by disrupting olfactory sensory neurons.

The researchers said antibodies may confer protection from Covid reinfection for at least six months, although these protective antibodies did not guarantee immunity, particularly for distinctly different Covid strains.

Loss of both smell and taste have been universally recognised as key symptoms of Covid infection.

“This study demonstrates that altered smell and taste are associated with a robust serologic response to SARS-CoV-2,” they wrote.

“The association remains significant when adjusting for other predictors of serologic response, including age and sex. These findings have important implications as we continue to combat the ongoing pandemic.

“Although vaccination efforts against Covid-19 have been successful in parts of the world, nearly half of the world’s population remains unvaccinated. Overall, examining factors associated with a serologic response to SARS-CoV-2 is an important step toward understanding the pathophysiology of this disease, identifying mechanisms of natural immunity, and developing targeted vaccines and global vaccination strategies.”

Understanding prevalence and duration of immunologic response among patients with history of Covid infection and individuals undergoing immunisation remained a priority, the researchers said.

“Results from our study suggest that loss of smell and taste during COVID-19 infection are strong predictive factors for a robust immunologic response based on IgG titers [blood tests],” they concluded.

“Additional research is needed to address the durability of seropositivity among these individuals.”

PLOS One 2022, online December 14