HealthDay News — Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibody levels are higher in previously infected individuals than in infection-naive individuals after one dose of the Pfizer/BioNTech (BNT162b2) vaccine, according to a research letter published online Aug. 6 in JAMA Network Open.
Mark Anderson, Ph.D., from Abbott Laboratories in Abbott Park, Illinois, and colleagues assessed the SARS-CoV-2 spike immunoglobulin (Ig)G antibody levels after one and two doses of BNT162b2 in 29 previously infected individuals compared with 30 infection-naive individuals. SARS-CoV-2 spike IgG antibody levels from plasma were measured at baseline and after receipt of one and two BNT162b2 doses.
The researchers found that infection-naive participants had mean SARS-CoV-2 spike receptor binding domain IgG levels of 4.03 AU/mL at baseline, which increased to 1,822 and 15,005 AU/mL after one and two vaccine doses, respectively. Mean IgG levels increased from 621.3 AU/mL at baseline to 30,173 and 36,600 AU/mL after doses 1 and 2, respectively, among previously infected individuals. Four individuals with previous infection reported a previous positive polymerase chain reaction (PCR) but did not develop antibodies. In these individuals, vaccine responses resembled those of infection-naive participants.
“In previously infected individuals with positive SARS-CoV-2 spike IgG levels, the second dose did not significantly increase IgG levels compared with the first dose, suggesting that one dose may be acceptable in this group,” the authors write. “However, it is important to note that a positive PCR diagnosis alone was not enough to discount the need for a second vaccine dose.”
Several authors are employees of Abbott Laboratories; the work was supported by Abbott Diagnostics Division Research and Development funding.