World news – Rapid Decay of IgA and IgM After COVID-19 Infection – Infectious Disease Advisor


A decline in immunoglobulin (Ig) A and IgM after Coronavirus Disease 2019 (COVID-19) has been observed among healthcare workers in Spain, according to a cross-sectional study published in the Journal of Infectious Diseases.

Healthcare workers (N = 566) from the Clínic de Barcelona Hospital, Barcelona, ​​Spain were randomly selected for the study. Participants received a nasopharyngeal swab and provided a blood sample at baseline, 1 month, and 3 months. The swabs were examined for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) by real-time polymerase chain reaction (RT-PCR) and the blood samples were examined for antibodies.

At the start of the study, 11.5% (65/566 ) of the participants evidence of a previous SARS-CoV-2 infection. Among workers who had no signs of infection, 71.7% were women, 53.5% had a mean age of 42 years, 11% reported previous COVID-19 symptoms, 21.2% had comorbidities, and 76.4 % worked directly with patients with COVID-19.

After 1 month, 14.9% of the participants had evidence of a previous SARS-CoV-2 infection. Overall, 10.1% of the samples were positive for IgM, 11.3% positive for IgG and 11.5% positive for IgA. Among previously uninfected participants, 5% were newly infected.

The likelihood of getting a positive COVID-19 test was related to the participant’s position in the hospital. Laboratory and other technicians had an increased risk of infection (odds ratio [OR], 13.3; 95% CI, 1.47–115.76; P = 0.048).

Among the samples that were COVID-19 positive in the first month, 77.55% were seroreverted for IgM, 3.70% for IgG and 24.53% for IgA by month 3. These rates corresponded to the reversal of at least 1 antibody in 6.1% of the individuals. IgG levels increased in 28 people between the start of the study and 1 month and in 6 people between month 1 and 3.

The antibody decay rates from baseline to 3rd month were 0.14 (95% CI, 0.11-0.18) for IgM, 0.66 (95% CI, 0.53-0.82) for IgG and 0.12 (95% CI, 0.09-0.16) for IgA. Seroreversion was projected to be 1.95 months (95% CI, 1.74-2.22; P <0.0001) for IgM, 19.41 months (95% CI, 12.84-39.75 ; P <0.0001) for IgG and 1.95 months (95%) occurs CI, 1.71-2.25; P <0.0001) for IgA.

Stratified by symptoms, IgA levels were higher in healthcare workers with COVID-19 compatible symptoms (P = 0.0008) and IgM levels were higher in patients with symptoms that persisted for more than 10 days (P = 0.0019). A COVID-19 compatible symptom during the follow-up month was associated with SARS-CoV-2 infection between months 0 and 1 (OR 6.55; 95% CI 2.77-14.44; P <0 , 0001).

These results may have been limited by the choice to use only 1 antigen for antibody testing.

« IgA levels are higher in symptomatic people than in asymptomatic [people], and IgM levels are positively correlated with the duration of symptoms. » Investigators came to the conclusion. IgA and IgM antibodies disintegrated quickly after a COVID-19 infection, especially in asymptomatic people or people with mild symptoms.

Moncunill G, Mayor A, Santano R, et al. SARS-CoV-2 seroprevalence and antibody kinetics among health care workers in a Spanish hospital after three months of follow-up. J Infect Dis. Published online November 11, 2020. doi: 10.1093 / infdis / jiaa696.

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