SARS-CoV-2 Antibodies Undetectable in Some Recovered Patients

By Amy Orciari Herman

Edited by David G. Fairchild, MD, MPH, and Jaye Elizabeth Hefner, MD

Levels of antibodies to SARS-CoV-2 vary widely in patients after recovery from novel coronavirus disease (COVID-19) — and in some patients, antibodies are undetectable — according to a study on the preprint server medRxiv.

Researchers in China measured SARS-CoV-2-specific neutralizing antibodies in 175 patients who had recovered from COVID-19. All patients had been hospitalized with confirmed, albeit "mild," infection. Antibodies were measured in plasma collected at the time of discharge.

Overall, 30% of patients had very low levels of SARS-CoV-2-specific antibodies; of these, 10 patients (6% overall) had undetectable antibody titers. Those with undetectable titers at discharge still had undetectable levels 2 weeks later.

Six patients had antibody titers measured at different points in their disease course. Titers peaked at roughly 10–15 days after illness onset and remained stable thereafter.

The researchers conclude, "These results revealed that a proportion of patients infected with SARS-CoV-2 would recover without developing high titers of virus-specific [neutralizing antibodies]. How these patients recovered without the help of [antibodies] and whether they were at risk of re-infection of SARS-CoV-2 should be further explored."

Infectious disease specialist Dr. Paul Sax weighed in: "Studies of serologic response after COVID-19 are in their infancy, and we should expect larger more representative analyses as antibody testing rapidly becomes more available. What's even less clear is how these responses (or lack of them) correlate with susceptibility to re-infection."