Neutralization of SARS-CoV-2 Variants by Serum from BNT162b2 Vaccine Recipients.

Fabrizia Valleriani,Alessio Lorusso,Giovanni Savini,Alessandra Leone,Barbara Bonfini,Daniela Morelli,Lisa Di Marcantonio,Elisa Mancuso,Massimo Spedicato,Liana Teodori,Giacomo Vincifori

doi:10.3390/v13102011

Abstract

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has evolved rapidly, leading to viral lineages characterized by multiple mutations in the spike protein, which could potentially confer to the virus the ability to avoid the vaccine-induced immune response, making the vaccines less effective or ineffective. Here, we initially evaluated the neutralization capabilities in vitro by serum neutralization (SN) of six serum samples collected from recipients of the BNT162b2 vaccine against 11 SARS-CoV-2 isolates belonging to the major SARS-CoV-2 lineages that had been circulating in Italy. Then, we considered 30 additional serum samples by SN assay against the dominant B.1.617.2 (Delta) variant. A B.1 lineage isolate was used as a reference. In the first analysis, significant differences when compared with the reference strain (p > 0.05) were not evidenced; instead, when the panel of 30 sera was tested against the B.1.617.2 (Delta) variant, a significant (p = 0.0015) 2.38-fold reduction in neutralizing titres compared with the reference after the first vaccine dose was demonstrated. After the second vaccine dose, the reduction was not significant (p = 0.1835). This study highlights that the BNT162b2 vaccine stimulates a humoral response able to neutralize all tested SARS-CoV-2 variants, thus suggesting a prominent role in mitigating the impact of the SARS-CoV-2 pandemic in real-world conditions. Long-term follow-up is currently ongoing.

Highlights

We evaluated the neutralization capabilities in vitro of serum samples collected from recipients of the BNT162b2 vaccine against isolates of the major SARS-CoV-2 variants circulating in Italy, including the last occurring B.1.617.2 (Delta) variant
We here demonstrate that neutralizing levels against both B.1.617.2 (Delta) isolates were significantly reduced only after the first dose of BNT162b2 vaccine with respect to the reference B.1 lineage isolate
After the second dose of vaccine, the mean titre against the B.1.617.2 (Delta) variant isolate was only slightly reduced with respect to the reference strain but without any statistical difference

Summary

Introduction

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the zoonotic agent causative of the COVID-19 pandemic [1], has evolved rapidly, leading to several viral lineages that are nowadays circulating worldwide. Some of these lineages gained international concern for their potential to escape preventive and therapeutic countermeasures. These certainly include the recent Delta (PANGO lineage B.1.617.2) variant. This variant was first detected in India in December 2020 and was initially considered a variant of interest [2]. Given its rate of spread, it is considered a variant of concern (VOC) from May

Methods

Results

Conclusion