SARS-CoV-2 antibody responses before and after a third dose of the BNT162b2 vaccine in Italian healthcare workers aged ≤60 years: One year of surveillance

Abstract

This study monitored the anti-spike-receptor-binding domain (RBD) and neutralizing antibodies induced by the Pfizer/BioNTech mRNA BNT162b2 vaccine in a cohort of 163 healthcare workers aged ≤60 years. We have taken advantage of two study groups, both of whom received the first two doses in the same time window, but Group 1 (54 HCWs) received the third dose 2 months before Group 2 (68 HCWs) did. The cohorts were monitored from the 12th day after the first vaccine dose up to 1 month after the third vaccine dose for a total of eight time points and about 1 year of surveillance (T1 = 12 days after the first dose; T2 = 10 days after the second dose; T3 = 1 month after the second dose; T4 = 3 months after the second dose; T5 = 4 months after the second dose; T6 = 5 months after the second dose; T7 = 7 months after the second dose; T8 = 1 month after the third dose for Group 1; T8* = 9 months after the second dose for Group 2; T9 = 1 month after the third dose for Group 2). The mean value of anti-spike antibodies decreased faster over time, but at T7, its decline was significantly slowed (T7 vs. T8*). After the third dose, the anti-spike titer rose about 34-fold (T7 vs. T8 and T8* vs. T9) and the booster improved the anti-spike titer by about three times compared with that of the second dose (T3 vs. T8 and T3 vs. T9), and no difference was noted between the two groups. The neutralizing titer was evaluated at T3, T7, T8, and T9. Anti-spike and neutralizing antibodies were found to be strongly correlated (r2 = 0.980; p < 0.001). At T3, 70% of the participants had a neutralizing antibody titer >91% of total anti-spike antibodies that increased to 90% after the third dose (T8 and T9). However, when the anti-spike titer reached its lowest value (T7), the neutralizing antibody levels decreased even further, representing only 44% of total anti-spike antibodies (p < 0.0001). Our findings show that the third vaccine dose improves the humoral response, but the wane of the anti-spike and neutralizing antibody titers over time is more marked in the neutralizing antibodies.

Mosaic sarbecovirus nanoparticles elicit cross-reactive responses in pre-vaccinated animals

“…Notably, RBD-nanoparticle immunizations in pre-immunized NHPs elicited high overall ELISA and neutralization titers against a diverse array of both matched and mismatched sarbecoviruses (Figure 2B-C; Figure S2B-C). As generally observed for vaccines, 29–31 we found that elicited Ab binding responses contracted after both RBD-nanoparticle and bivalent repRNA immunizations (5-8 fold from week 2 to week 8) and after boosting (∼10 fold from week 10 to week 22). Contractions in binding Ab levels largely correlated with drops in neutralizing Ab titers (Figure 2B-C; Figure S2B-C).…”

Neutralizing Antibody Response following a Third Dose of the mRNA-1273 Vaccine among Cancer Patients

“…Even after two doses of a COVID-19 vaccine, patients with cancer have lower total antibody geometric mean titers (GMTs) than healthy adults, and the immune response decreases around 6 months following vaccination [ 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 ]. Central to the vaccine-elicited immune response are neutralizing antibodies, which have also been shown to decrease and be insufficient following only two vaccine doses in cancer patients [ 11 , 12 , 13 ]. The benefit of the third vaccine dose for at-risk populations has been shown via an increase in total antibody GMT [ 2 , 14 , 15 , 16 , 17 ].…”