evidence: The COVID-19 pandemic necessitated the rapid production of vaccines aimed at the production of neutralizing antibodies against the COVID-19 spike protein required for the corona virus binding to target cells. The best well-known vaccines have utilized either mRNA or an adenovirus vector to direct human cells to produce the spike protein against which the body produces mostly neutralizing antibodies. However, recent reports have raised some skepticism as to the biologic actions of the spike protein and the types of antibodies produced. One paper reported that certain antibodies in the blood of infected patients appear to change the shape of the spike protein so as to make it more likely to bind to cells, while other papers showed that the spike protein by itself (without being part of the corona virus) can damage endothelial cells and disrupt the blood-brain barrier. These findings may be even more relevant to the pathogenesis of long-COVID syndrome that may affect as many as 50% of those infected with SARS-CoV-2. In COVID-19, a response to oxidative stress is required by increasing anti-oxidant enzymes. In this regard, it is known that polyphenols are natural anti-oxidants with multiple health effects. [...] Could SARS-CoV-2 Spike Protein Be Responsible for Long-COVID Syndrome?Mol Neurobiol. 2022 Mar;59(3):1850-1861. doi: 10.1007/s12035-021-02696-0. Epub 2022 Jan 13. Mol Neurobiol. 2022. PMID: 35028901 Free PMC article. Review. [...] Adenovirus Vaccine Containing Truncated SARS-CoV-2 Spike Protein S1 Subunit Leads to a Specific Immune Response in Mice.Vaccines (Basel). 2023 Feb 13;11(2):429. doi: 10.3390/vaccines11020429. Vaccines (Basel). 2023. PMID: 36851306 Free PMC article.