Vaccines have been seen as the most important solution for ending the coronavirus disease 2019 (COVID‐19) pandemic. The aim of this study is to evaluate the antibody levels after inactivated virus vaccination. We included 148 healthcare workers (74 with prior COVID‐19 infection and 74 with not). They received two doses of inactivated virus vaccine (CoronaVac). Serum samples were prospectively collected three times (Days 0, 28, 56). We measured SARS‐CoV‐2 IgGsp antibodies quantitatively and neutralizing antibodies. After the first dose, antibody responses did not develop in 64.8% of the participants without prior COVID‐19 infection. All participants had developed antibody responses after the second dose. We observed that IgGsp antibody titers elicited by a single vaccine dose in participants with prior COVID‐19 infection were higher than after two doses of vaccine in participants without prior infection (geometric mean titer: 898 and 607 AU/ml). IgGsp antibodies, participants with prior COVID‐19 infection had higher antibody levels as geometric mean titers at all time points (p < 0.001). We also found a positive correlation between IgGsp antibody titers and neutralizing capacity (rs = 0.697, p < 0.001). Although people without prior COVID‐19 infection should complete their vaccination protocol, the adequacy of a single dose of vaccine is still in question for individuals with prior COVID‐19. New methods are needed to measure the duration of protection of vaccines and their effectiveness against variants as the world is vaccinated. We believe quantitative IgGsp values may reflect the neutralization capacity of some vaccines.
Background It is essential to know about immune response levels after booster doses of the two different types of vaccines, mRNA, and the inactivated, currently used against COVID‐19. For this purpose, we aimed to determine the effects of BNT162b2 (BNT) and CoronaVac (CV) boosters on the humoral and cellular immunity of individuals who had two doses of CV vaccination. Methods The study was conducted in three centers (Koc University Hospital, Istanbul University Cerrahpasa Hospital, and Istanbul University, Istanbul Medical School Hospital) in Istanbul, Turkey. Individuals who had been previously immunized with two doses of CV and no history of COVID‐19 were included. The baseline blood samples were collected 3–5 months after the second dose of CV. Follow‐up blood samples were taken 1 and 3 months after administration of third doses of CV, or one dose of BNT boosters. Neutralizing antibody titers were measured by plaque reduction assay. The CD4+ T cell, CD8+ T cell, effector CD4+CD38+CD69+ T cell, and effector CD8+CD38+CD69+ T cell ratios were determined by flow cytometry. The intracellular IFN‐γ and IL‐2 responses were measured by ELISpot assay. Results We found a 3.38‐fold increase in neutralizing antibody geometric mean titers (NA GMT, 78.69) 1 month after BNT booster and maintained at the third month (NA GMT, 80). Nevertheless, in the CV booster group, significantly lower NA GMT than BNT after 1 month and 3 months were observed (21.44 and 28.44, respectively) ( p < .001). In the ELISpot assay, IL‐2 levels after BNT were higher than baseline and CV booster ( p < .001) while IFN‐γ levels were significantly higher than baseline ( p < .001). The CD8+CD38+CD69+ and CD4+CD38+CD69+ T cells were stimulated predominantly in the third month of the BNT boosters. Conclusion The neutralizing antibody levels after 3 months of the BNT booster were higher than the antibody levels after CV in fully vaccinated individuals. On the contrary, ratio of the effector T cells increased along with greater IFN‐γ activation after BNT booster. By considering the waning immunity, we suggest a new booster dose with BNT for the countries that already had two doses of primary CV regimens.
We evaluated neutralizing antibodies against the Omicron variant and Anti-Spike IgG response in solid organ (SOT) or hematopoietic stem cell (HSTC) recipients after a third dose of BNT162b2 (BNT) or CoronaVac (CV) following two doses of CV. In total, 95 participants underwent SOT (n = 62; 44 liver, 18 kidney) or HSCT (n = 27; 5 allogeneic, 22 autologous) were included from five centers in Turkey. The median time between third doses and serum sampling was 154 days (range between 15 to 381). The vaccine-induced antibody responses of both neutralizing antibodies and Anti-Spike IgGs were assessed by plaque neutralizing assay and immunoassay, respectively. Neutralizing antibody and Anti-Spike IgG levels were significantly higher in transplant patients receiving BNT compared to those receiving CV (Geometric mean (GMT):26.76 vs. 10.89; p = 0.03 and 2116 Au/mL vs. 172.1 Au/mL; p < 0.001). Solid organ transplantation recipients, particularly liver transplant recipients, showed lower antibody levels than HSCT recipients. Thus, among HSCT recipients, the GMT after BNT was 91.29 and it was 15.81 in the SOT group (p < 0.001). In SOT, antibody levels after BNT in kidney transplantation recipients were significantly higher than those in liver transplantation recipients (GMT: 48.32 vs. 11.72) (p < 0.001). Moreover, the neutralizing antibody levels after CV were very low (GMT: 10.81) in kidney transplantation recipients and below the detection limit (<10) in liver transplant recipients. This study highlights the superiority of BNT responses against Omicron as a third dose among transplant recipients after two doses of CV. The lack of neutralizing antibodies against Omicron after CV in liver transplant recipients should be taken into consideration, particularly in countries where inactivated vaccines are available in addition to mRNA vaccines.
Introduction: We evaluated neutralizing antibody and anti-spike antibody (anti-S) response against omicron variant in solid organ (SOT) or hematopoietic stem cell (HSTC) receivers after third dose of BNT162b2 (BNT) or CoronaVac (CV) following two doses of CV. Methods: In total, 95 participants who underwent SOT (n=62; 44 liver, 18 kidney) or HSCT (n=27; 5 allogeneic, 22 autologous) were included from five centers in Turkey. The median time between third doses and serum sampling was 154 days. The vaccine-induced antibody responses of both neutralizing antibodies and Anti-Spike antibodies were assessed by plaque neutralizing assay and immunoassay. Results: Neutralizing antibody and anti-spike IgG levels were significantly higher in transplant patients receiving BNT compared to those receiving CV (GMT:26.76 vs 10.89; p=0.03 and 2116 Au/ml vs 172.1 Au/ml; p<0.001). Solid organ transplantation recipients, particularly liver transplant recipients, showed lower antibody levels than HSCT recipients. Thus, among HSCT recipients, the GMT after BNT was 91.29 and it was 15.81 in the SOT group (p<0.001). In SOT, antibody levels after BNT in kidney transplantation recipients was significantly higher than that in liver transplantation recipients (GMT:48.32 vs 11.72) (p<0.001). Besides, the neutralizing antibody levels after CV were very low (GMT: 10.81) in kidney transplantation recipients and below the detection limit (<10) in liver transplant recipients. There was a weak correlation between the neutralizing and anti-Spike antibody responses (r=0.36). Conclusion: This study highlights the superiority of BNT responses against omicron as a third dose among transplant recipients after two doses of CV. Lack of neutralizing antibody against omicron after CV in liver transplant recipients should be taken into consideration particularly in countries where inactivated vaccines are available in addition to mRNA vaccines.
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