1003: Pfizer will get $1.95 billion from the U.S. government to produce 100 million doses of their COVID-19 vaccine candidate. (Reuters)1004: More data suggested humoral immunity faded quickly in people with mild COVID-19 illness. (New England Journal of Medicine) 1005: Small study suggests rapid decay of anti–SARS-CoV-2 antibodies in persons with mild COVID-19
DG Alert: Findings from a study published in The New England Journal of Medicine “raise concern” that humoral immunity against SARS-CoV-2 may not be long lasting in persons with mild illness. Javier Ibarrondo, David Geffen School of Medicine at University of California, Los Angeles, California, and colleagues evaluated 34 persons (20 females and 14 males; mean age: 43 years, [range, 21 to 68]). Of these, 30 participants had their infection confirmed by PCR, while the other 4 participants had CLI. Most of the participants had mild illness.
A total of 31 of the 34 participants had two serial measurements of IgG levels, while the remaining 3 participants had three serial measurements. The first measurement was obtained at a mean of 37 days after the onset of symptoms (range, 18 to 65), and the last measurement was obtained at a mean of 86 days after the onset of symptoms (range, 44 to 119).
The initial mean IgG level was 3.48 log10 ng per milliliter (range, 2.52 to 4.41). On the basis of a linear regression model that included the participants’ age and sex, the days from symptom onset to the first measurement, and the first log10 antibody level, the estimated mean change (slope) was reported to be −0.0083 log10 ng per milliliter per day (range, −0.0352 to 0.0062). The authors noted that this corresponds to a half-life of approximately 73 days over the observation period. Further, they reported that the 95% confidence interval for the slope was −0.0115 to −0.0050 log10 ng per milliliter per day (half-life, 52 to 120 days).
The protective role of antibodies against SARS-CoV-2 is unknown, but these antibodies are usually a reasonable correlate of antiviral immunity, and anti–receptor-binding domain antibody levels correspond to plasma viral neutralizing activity. Given that early antibody decay after acute viral antigenic exposure is approximately exponential, we found antibody loss that was quicker than that reported for SARS-CoV-1.