Humoral response to the BNT162b2 second and third vaccine doses
After the second vaccine dose, 37 patients and 23 controls provided
serum samples for immunogenicity; 36 patients and 14 controls provided
serum samples 6 months later. A total of 9 patients and 9 controls
provided samples after the third vaccine. The dynamics of the S1/S2
antibody level among both study groups are presented in Figures 1 and 2.
Among the control group, the seropositivity rate was 100% at all three
time points. Anti-S1/S2 antibody titres declined at 6 months after the
second vaccine from a mean of 388.3 (SD 56.09) BAU/ml to 212.93 (SD
93.69) BAU/ml, and was restored shortly after the third vaccine dose, to
400 (SD 0) BAU/ml. As expected, the seropositivity rate was lower among
AIIRD patients compared to controls, 91% at 2-8 weeks and 87% at 6
months after the second vaccination, and returned to 100% following the
third dose. Anti-S1/S2 antibody titres declined at 6 months after the
second vaccine from a mean of 243.1 (SD 140.8) BAU/ml to 216.9 (SD
157.6) BAU/ml, and increased shortly after the third vaccine dose to
355.8 (SD 126.4) BAU/ml. In comparison to the control group, anti-S1/S2
antibody titres among the patients were significantly lower only at 2–8
weeks after the second vaccine dose (p<0.0001) and comparable
at the subsequent 6-month follow-up after the second, and 2-8 weeks
after the third dose. Notably, the decline of the anti-S1/S2 antibody
titres within 6 months after the second vaccine dose was significantly
steeper among the controls compared to patients, with a mean of -197 (SD
87.4) vs. -61.2 (SD 151.4), p=0.0197, respectively. In the limited
sample of controls (n=5) and patients (n=2) with available serologic
data, the increase in the antibody titre after the third vaccine dose
was comparable in both groups.
Patients with JIA maintained the highest level of anti-S1/S2 antibody at
all time-points, whereas the lowest anti-S1/S2 antibody levels were
found among patients with vasculitis and scleroderma (Supplement Table
2).
Analysis of humoral response according to the use of anti-rheumatic
medications showed that patients treated with csDMARDs and bDMARDs
developed a comparable humoral response at all points tested. Among 17
patients treated with TNFi, those treated with TNFi monotherapy achieved
numerically higher anti-S1/S2 antibody levels than those treated with
combination therapy. MMF was most strongly associated with blunted
humoral response to vaccination after the second vaccine dose (115± 89).
The humoral response following the third vaccine dose evaluated in 2 of
6 patients treated with MMF was completely restored. Notably, 4 patients
treated with anti-CD20 therapy (RTX), 2 patients with AAV, 1 patient
with SLE, and 1 with systemic sclerosis developed an adequate
seropositive response after the second vaccine dose, with the steepest
decline in anti-S1/S2 antibody levels within 6 months, compared to
antibody kinetics of patients treated with other medications. The
humoral response following the third vaccine dose evaluated in one of
these patients was completely restored. Patients treated with RTX were
vaccinated 6 months after the last RTX dose and before the next dose.