**5. The relationship between COVID-19 vaccination and cognitive functions**

Major neurocognitive disorders are higher in the elderly population. This disease is higher in patients over 60 years old, especially over 80 years of age. In addition, this age group is more sensitive to infections. Immune dysregulation causes a decreased vaccine-associated immune reaction in these patients. Increased age is associated with decreased immunity and increased risk of complications. International investigations have been initiated to accelerate the development of vaccines and medications for the COVID-19 pandemic. These results suggest a different vaccination protocol, especially with increased age. Because this group is highly sensitive to major neurocognitive disorders and other diseases [61].

More cases of adverse reactions after COVID-19 vaccination are being reported. One of the adverse reactions is neurocognitive disorders after vaccination. However, neurocognitive disorders are lower after COVID-19 vaccines. In a recent case report, two cases of encephalopathy were reported within one week after mRNA vaccination [62]. In addition, delirium was reported in an 89-year-old patient after the first dose of the mRNA vaccine [63]. The mechanism of the disease is systemic inflammation associated with anti-spike antibodies and macrophage activation after mRNA vaccines [62–64]. However, there is no case-control study on this subject.

*COVID-19 Pandemic and Neurocognitive Process: New Scenarios for Understanding… DOI: http://dx.doi.org/10.5772/intechopen.106687*

Most of the immunogenic epitopes of SARS-CoV-2 are similar to human proteins. Vaccines with these epitopes have more risk for autoimmunity [65]. Increased inflammation and biochemical reactions associated with autoimmunity can cause neuroinflammation and cognitive impairment [66]. Experimental studies have demonstrated that there is a relationship between increased autoimmunity and cognitive impairment [67]. However, all these evaluations demonstrate that there is no definite relationship between vaccination and cognitive dysfunction.
