Nwokike et al. World Journal of Pharmaceutical Research www.wjpr.net │ Vol 11, Issue 10, 2022. │ ISO 9001:2015 Certified Journal │ THE PLACEBO AND NOCEBO FACTORS OF COVID-19 VACCINE EFFICACY M. O. Nwokike 1 *, S. I. Ghasi 2 , M. N. Ezenwaeze 3 , A.O. Ogbonna 4 and A.C. Ezinwa 3 1 Department of Pharmacology and Therapeutics, Ebonyi State University, Abakaliki, Nigeria. 2 Department of Pharmacology and Therapeutics, University of Nigeria, Enugu, Nigeria. 3 Department of Pharmacology and Therapeutics, Enugu State University, Nigeria. 4 Government House Hospital, Enugu, Nigeria. ABSTRACT Disturbances in which emotional maladjustment leads to dysfunction in some organ system can lead to illness. Positive emotional adjustment towards a therapy can bring about positive outcomes without recourse to the known potency of the administered substance. The contrary is also the case where negative emotional adjustment towards a therapy can bring about negative clinical outcomes. These effects are referred to as the placebo and nocebo effects respectively. Placebos have the appearance of being real but lack the capacity to perform as expected when applied in situations. Nocebos on the other hand are known for having a tendency to cause harm especially based on expectation from societal cues. Some of the successes attributed to Covid-19 vaccines are ascribed to the expectation that the vaccines will work while many adverse events and death have been associated with coerced vaccinations in the face of vaccine hesitancy. This review highlights the evidence showing that some people do feel or get better after taking Covid-19 vaccines, while some other people display unexpected or severe adverse effect after the same therapy mostly due to their mental or emotional disposition. KEYWORDS: Covid-19 Vaccine, Nocebo, Placebo Response, Placebo Responders, Placebo Effect. World Journal of Pharmaceutical Research SJIF Impact Factor 8.084 Volume 11, Issue 10, XXX-XXX. Review Article ISSN 2277– 7105 *Corresponding Author M. O. Nwokike Department of Pharmacology and Therapeutics, Ebonyi State University, Abakaliki, Nigeria. matthew.nwokike@gmail.com Article Received on 28 May 2022, Revised on 18 June 2022, Accepted on 08 July 2022 DOI: 10.20959/wjpr202210-24145