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
Key PointsO_ST_ABSQuestionC_ST_ABSWhat is the median time to clearance of SARS-CoV-2 among cancer patients according to currently used criteria? FindingsIn this single-institution retrospective cohort study, the median time to SARS-CoV-2 clearance was 50 days using the ASCO/CDC criteria of 2 negative RT-PCR assays >24 hours apart. Using alternative criteria of 1 negative RT-PCR assay (UK-NICE) or CDC clinical criteria (10 days after first positive RT-PCR and 3 days after last symptoms), median clearance times were 31 days and 13 days, respectively. MeaningSARS-CoV-2 clearance times differ substantially depending on criteria used and may be prolonged in cancer patients.