Link between S- and N-Protein IgG levels after the first
BNT162b2 dose
Among the RT-PCR-positive residents, the median levels of S-protein IgG
after vaccine were ranked in the following order: i ) residents
with a newer infection and no detectable N-protein IgG (median value of
230AU/mL), ii ) residents with a newer infection and detectable
N-protein IgG (median value of 20,685 AU/mL), iii ) residents with
an older infection and no detectable N-protein IgG (median value of
27,313 AU/mL), and iv ) residents with an older infection and
detectable N-protein IgG (median value of 40,000 AU/mL)(Table 2, Figure
2).
The predictive value of a high S-protein IgG level (≥ 4,160 UA/ ml) by
N-protein IgG (≥ 0.8 signal to cutoff ratio) was high (positive
predictive value of 92.5% [90.8%-94.2%] and negative predictive
value of 93.0% [91.4%-94.6%]).
S-protein IgG levels 6 weeks after the second BNT162b2
jab
Six weeks after the second BNT162b2 jab, only around 3% of the 554
residents without prior COVID-19 had undetectable S-protein IgG levels
(< 50 AU/mL) vs none of the residents with a prior positive
PCR (Table 3). The prevalence of residents with low S-protein IgG levels
(≤ 1,050 AU/mL) was significantly lower in residents without prior
COVID-19 than in those with a positive PCR in the 3 to 12 last months
(28.3% vs 2.7%, p<0.001) (Figure 3). The median value of
S-protein IgG in residents without prior COVID-19 after two vaccine
doses was 10-fold lower than that in residents with prior COVID-19 after
one dose (2,384 AU/mL vs 23,259 AU/mL)