Does ChAdOx1-S and BNT162b2 heterologous prime-boost vaccination trigger higher rates of vaccine-related adverse events?

Background: There has been significant international interest in heterologous prime-boost COVID-19 vaccination. However, it is linked with different intensity and frequency of adverse events. This study aimed to assess the safety of ChAdOx1-S and BNT162b2 vaccines when given as heterologous prime-boost vaccination in Saudi Arabia. Methods: A cross-sectional study was conducted during the period October 2021 to March 2022. The study included two groups of people based on the type of vaccination regimen. The first group (heterologous) was subjected to different prime-boost vaccination schedules irrespective of the prime and boost vaccine types. The second group included people vaccinated with the same type of COVID-19 vaccine (homologous). Results: The overall sample included 334 participants. Those included in the heterologous group were at about 1.5 fold -increased risk for developing local and systemic adverse events compared to the homologous group. Fever, headache, and vomiting were significantly more frequent among the heterologous group compared to the homologous group (p-value<0.05). In both groups, more than half of the recorded adverse events were mild/moderate in severity. Conclusion: Heterologous prime-post vaccination is associated with a slightly increased risk for the development of local and systemic adverse events compared to the homologous regimen. However, most of these adverse events are mild/moderate in nature and recede within two days with no serious adverse events documented.

Discovery of New Fusion Inhibitor Peptides against SARS-CoV-2 by Targeting the Spike S2 Subunit.

A novel coronavirus, severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), caused a worldwide pandemic. Our aim in this study is to produce new fusion inhibitors against SARS-CoV-2, which can be the basis for developing new antiviral drugs. The fusion core comprising the heptad repeat domains (HR1 and HR2) of SARS-CoV-2 spike (S) were used to design the peptides. A total of twelve peptides were generated, comprising a short or truncated 24-mer (peptide #1), a long 36-mer peptide (peptide #2), and ten peptide #2 analogs. In contrast to SARS-CoV, SARS-CoV-2 S-mediated cell-cell fusion cannot be inhibited with a minimal length, 24-mer peptide. Peptide #2 demonstrated potent inhibition of SARS-CoV-2 S-mediated cell-cell fusion at 1 µM concentration. Three peptide #2 analogs showed IC50 values in the low micromolar range (4.7-9.8 µM). Peptide #2 inhibited the SARS-CoV-2 pseudovirus assay at IC50=1.49 µM. Given their potent inhibition of viral activity and safety and lack of cytotoxicity, these peptides provide an attractive avenue for the development of new prophylactic and therapeutic agents against SARS-CoV-2.