Dear Editor,
Since September 2020, the COVID-19 disease pandemic affected population around the world; as of May 2024, there have been 704 753 890 infections and 7 010 681 deaths in humans recorded worldwide. Health authorities around the world recommended measures such as social distancing, quarantine, and vaccination to reduce the spread and control the disease.1 Unfortunately, COVID-19 pandemic has led to collateral psychological disorders such as anxiety, obsession, fear, depression, and stress.2 One of the most important consequences of mental complications is the effect of this disease on the human immune system. In line with a complex relationship between the immune, endocrine, and nervous systems, numerous evidences show that anxiety and stress through hypothalamic–pituitary–adrenal axis can lead to impairment of the regulation of the immune system.3
In this regard, people who had severe mental complications during the COVID-19 pandemic are likely to be susceptible to complications and death from mental disease. In association with the COVID-19 vaccine, the Food and Drug Administration recently stated that an approved vaccine must be at least 50% more effective than a placebo group.4 Since the doubt about the elimination of diseases by means of a vaccine caused the World Health Organization to include vaccine hesitancy as one of the 10 threats related to the global health.5 Identifying and understanding the psychological characteristics that define hesitant people is important to be able to adopt corrective measures. Psychological characteristics have an effective role on the immune response or on side effects of the COVID-19 vaccines, hence, affecting vaccine effectiveness.6
Psychological, social, and behavioral factors significantly influence the immune response to the vaccine, so it is very important to control and evaluate the psychological properties of the vaccinated subjects. According to the studies, although the occurrence of side effects of vaccination such as lethargy, headache, pain at the injection site, and loss of appetite are common in vaccinated people, but these symptoms last longer in cases with mental disorders.3 It is not unlikely that people who have experienced severe stress, anxiety, and depression during the COVID-19 pandemic, may show an inadequate level of immunity to the SARS-CoV-2 virus.
Murphy et al. evaluated the relationship between hesitancy and people's resistance to vaccination. The participants in this study were from both Ireland (1041 persons) and England (2025 persons) countries; their results showed that considering the important role of psychological factors in vaccine injection, 35% and 31% of the participants from Ireland and England were hesitant to inject the COVID-19 vaccine, respectively.6 In another study, Madison et al. assessed the effect of mental factors on the effectiveness of corona virus vaccine. In this study, they evaluated the researches related to the role of mental characteristics on the safety of vaccine and immune system in the last 30 years. Their results showed the negative effects of psychological disorders such as anxiety, obsession, fear, depression, and stress on the immune response of vaccinated subjects, especially in women, elderly, and people affected by chronic diseases.7
In conclusion, given the significant role of mental characteristics on the efficacy of the immune response, it is recommended that the psychological interventions should be adopted for vulnerable groups (e.g., elderly and people with chronic diseases), people with a history of mental disorders, and also healthcare workers. Obviously, psychological characteristics also influence the acceptance or refusal of the vaccine. In addition, we need further large-scale investigations to evaluate the physiological characteristics of COVID-19 vaccines on vaccinated individuals to obtain more accurate and realistic results.
FundingNot applicable.
Author's contributionAll authors have actively contributed in writing, editing and revision of the manuscript.
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