Inhibition of receptor‐binding domain—ACE2 interaction after two doses of Sinovac's CoronaVac or AstraZeneca/Oxford's AZD1222 SARS‐CoV‐2 vaccines

Abstract

Practical laboratory proxies that correlate to vaccine efficacy may facilitate trials, identify nonresponders, and inform about boosting strategies. Among clinical and laboratory markers, assays that evaluate antibodies that inhibit receptor-binding domain (RBD) ligation to angiotensin-converting enzyme-2 receptor (receptor-binding inhibition [RBI]) may provide a surrogate for viral neutralization assays. We evaluated RBI before and after a median of 34 days (interquartile range [IQR]: 33-40) of the second dose of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Sinovac's CoronaVac (CN) or As-traZeneca/Oxford's AZD1222 (AZ) vaccines in 166 individuals. Both vaccines elicited high inhibitory titers in most subjects, 95% (158/166), with signal inhibition above 30% and 89% (127/143) with more than fourfold increase from prevaccination titers, but titers tend to decrease over time. Both postvaccination inhibitory titers (95%, IQR 85%-97% for AZ vs. 79%, IQR 60%-96% for CN, p = 0.004) and pre/post-titer increase (AZ 76%, IQR 51%-86% for AZ vs. 47%, IQR 24%-67% for CN, p < 0.0001) were higher among AZ vaccinees. Previous serological reactivity due to natural infection was associated with high prevaccination signal inhibition titers. The study documents a robust antibody response capable of interfering with RBD-angiotensin-converting enzyme binding. Evaluation of SARS-CoV-2 infection incidence in these populations is necessary to assess its association to protection and its duration.

Application of Traditional Vaccine Development Strategies to SARS-CoV-2

“…Therefore, IWV vaccines have played an important role in vaccine access during the initial phase of vaccination against COVID-19, but many IWV vaccinees may receive booster doses developed with emergent vaccine technologies like DNA and mRNA. In head-to-head comparisons, these types of vaccines were typically found to outperform IWV vaccines (for examples, see references 80 , 82 , and 136 ). At the same time, IWV vaccines are among the easiest to store and transport due to requiring refrigeration only at 2 to 8°C and remaining stable for years at a time ( 95 ).…”

An unexpected IgE anti-Receptor binding domain response following natural infection and different types of SARS-CoV-2 vaccines

“…Similarly, other studies have demonstrated IgE-responses independent of aluminum salts, as seen with Flu and MMR vaccines. 14,15 The overall IgE levels seems to re ect the IgG response observed in the cohort from where the samples of this study were obtained: 27 subjects with COVID-19 history before vaccination showed slightly elevated antibodies levels after the two ChAdOx1 or CoronaVac doses;…”

“…For natural infection analysis we analyzed sera samples from con rmed COVID-19 (Cov) cases collected 24 (10-32) days after diagnosis by RT-qPCR in 2020, as described previously. 27 These samples were compared with specimens obtained from volunteers without documented COVID-19 (Non-cov). Cov and Non-cov volunteers were discriminated through molecular and serological tests, which were routinely carried out between March and December 2020, regardless of the presence of symptoms during this period.…”

Evaluation of long-term antibody kinetics in healthcare workers vaccinated with inactivated COVID-19 Vero cell vaccine (CoronaVac), a propensity score-matched observational study

“…Long-term antibody responses are still uncertain after Coron-aVac vaccination, as most studies evaluate the short-term nAb responses ( Bichara et al, 2021 ;Chen et al, 2022 ;Ş enol Akar et al, 2021 ;Silva et al, 2021 ;Soysal et al, 2021 ). When the CoronaVac studies are evaluated, the longest follow-up period is 8 weeks after the second vaccination dose.…”