ABSTRACT
The Omicron Variant of Concern (B.1.1.529) has spread internationally and is raising serious concerns about reduced vaccine efficacy and the increased risk of reinfection. We assessed the serum neutralizing activity using a pseudovirus-based neutralization assay in 292 healthcare workers who had received a homologous booster dose of BBIBP-CorV vaccine, 8 to 9 months after completing the priming two-dose vaccination schedule, to investigate whether the newly identified Omicron variant can escape serum antibody neutralization induced by the booster vaccination. The booster dose of BBIBP-CorV rapidly induced a significantly high level of humoral immune response, and the neutralization geometric mean titer (GMT) against the wild-type strain on day 28 after the booster dose was 294.85 (252.99-343.65), 6.1 times higher than the level on day 28 after the second dose. The neutralization against the Omicron variant was also improved by the booster vaccination, although the GMT showed an approximately 20.1-fold reduction to 14.66 (12.30-17.48) when compared with the wild-type strain. This study demonstrated that a booster dose of BBIBP-CorV led to a significant rebound in neutralizing immune response against SARS-CoV-2, while the Omicron variant showed partial resistance to neutralizing antibodies induced by the booster vaccination.
ABSTRACT
We assessed the safety and immunogenicity of an inactivated SARS-CoV-2 vaccine BBIBP-CorV, especially measured the resistance of four global variants of concern: Lineage B.1.1.7, Lineage B.1.351, Lineage P.1, and Lineage B.1.526 to neutralizing activity of vaccine-elicited sera. Among 1006 enrolled participants, no serious adverse event was reported within 28 days post-vaccination. Seroconversion of neutralizing antibodies was seen in 698 (91.84%) of 760 healthcare workers, and the geometric mean titres (GMTs) of neutralizing antibody titre was 62.68 (57.02–68.91) after the second immunization. We found that 57 (12.13%), 99 (20.97%), and 114 (24.26%) vaccine-elicited sera showed complete or partial loss of neutralizing activity against lineage B.1.1.7, lineage B.1.526, and lineage P.1, respectively, while 199 (42.34%) vaccine-elicited sera preserved neutralizing activity against lineage B.1.351, albeit at relatively low dilutions. These data indicated that humoral responses against SARS-CoV-2 could be effectively induced in vaccine recipients, although diminished neutralization potency against multiple variants was observed.
ABSTRACT
Currently, there are no approved specific antiviral agents for 2019 novel coronavirus disease (COVID-19). In this study, ten severe patients confirmed by real-time viral RNA test were enrolled prospectively. One dose of 200 mL convalescent plasma (CP) derived from recently recovered donors with the neutralizing antibody titers above 1:640 was transfused to the patients as an addition to maximal supportive care and antiviral agents. The primary endpoint was the safety of CP transfusion. The second endpoints were the improvement of clinical symptoms and laboratory parameters within 3 days after CP transfusion. The median time from onset of illness to CP transfusion was 16.5 days. After CP transfusion, the level of neutralizing antibody increased rapidly up to 1:640 in five cases, while that of the other four cases maintained at a high level (1:640). The clinical symptoms were significantly improved along with increase of oxyhemoglobin saturation within 3 days. Several parameters tended to improve as compared to pre-transfusion, including increased lymphocyte counts (0.65*109/L vs. 0.76*109/L) and decreased C-reactive protein (55.98 mg/L vs. 18.13 mg/L). Radiological examinations showed varying degrees of absorption of lung lesionswithin 7 days. The viral load was undetectable after transfusion in seven patients who had previous viremia. No severe adverse effects were observed. This study showed CP therapy was welltolerated and could potentially improve the clinical outcomes through neutralizing viremia in severe COVID-19 cases. The optimal dose and time point, as well as the clinical benefit of CP therapy, needs further investigation in larger well-controlled trials.