Review A Review on Current COVID-19 Vaccines and Evaluation of Particulate Vaccine Delivery Systems Sarthak M. Shah 1 , Hashem O. Alsaab 2 , Mutasem M. Rawas-Qalaji 3,4,5 and Mohammad N. Uddin 1, *   Citation: Shah, S.M.; Alsaab, H.O.; Rawas-Qalaji, M.M.; Uddin, M.N. A Review on Current COVID-19 Vaccines and Evaluation of Particulate Vaccine Delivery Systems. Vaccines 2021, 9, 1086. https:// doi.org/10.3390/vaccines9101086 Academic Editor: François Meurens Received: 21 July 2021 Accepted: 24 September 2021 Published: 27 September 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1 College of Pharmacy, Mercer University, Atlanta, GA 31207, USA; Sarthak.Modi.Shah@live.mercer.edu 2 Department of Pharmaceutics and Pharmaceutical Technology, Taif University, P.O. Box 11099, Taif 21944, Saudi Arabia; mqalaji@sharjah.ac.ae 3 College of Pharmacy, University of Sharjah, Sharjah 26666, United Arab Emirates; h.alsaab@tu.edu.sa 4 Research Institute for Medical and Health Sciences, University of Sharjah, Sharjah 26666, United Arab Emirates 5 Dr. Kiran C. Patel College of Allopathic Medicine, Nova Southeastern University, Fort Lauderdale, FL 27272, USA * Correspondence: uddin_mn@mercer.edu; Tel.: +1-678-547-6224 Abstract: First detected in Wuhan, China, a highly contagious coronavirus, severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), also known as COVID-19, spread globally in December of 2019. As of 19 September 2021, approximately 4.5 million people have died globally, and 215 million active cases have been reported. To date, six vaccines have been developed and approved for human use. However, current production and supply capabilities are unable to meet global demands to immunize the entire world population. Only a few countries have been able to successfully vaccinate many of their residents. Therefore, an alternative vaccine that can be prepared in an easy and cost-effective manner is urgently needed. A vaccine that could be prepared in this manner, as well as can be preserved and transported at room temperature, would be of great benefit to public health. It is possible to develop such an alternative vaccine by using nano- or microparticle platforms. These platforms address most of the existing vaccine limitations as they are stable at room temperature, are inexpensive to produce and distribute, can be administered orally, and do not require cold chain storage for transportation or preservation. Particulate vaccines can be administered as either oral solutions or in sublingual or buccal film dosage forms. Besides improved patient compliance, the major advantage of oral, sublingual, and buccal routes of administration is that they can elicit mucosal immunity. Mucosal immunity, along with systemic immunity, can be a strong defense against SARS-CoV-2 as the virus enters the system through inhalation or saliva. This review discusses the possibility to produce a particulate COVID vaccine by using nano- or microparticles as platforms for oral administration or in sublingual or buccal film dosage forms in order to accelerate global vaccination. Keywords: COVID-19; vaccines; SARS-CoV-2; pandemic; oral particulate vaccine 1. Introduction The first coronavirus was discovered by Tyrell and Bynoe in the 1960s [1]. In 1967, McIntosh et al. reported the finding of several other strains of the virus [2]. Due to their bulbous, crown-shaped surface projections, the name “coronavirus” was announced as a new genus to describe these viruses [1,3]. Decades later, coronaviruses made head- lines again when the first instance of the 2019 novel coronavirus was detected in Wuhan, China [4]. Later that month, a travel-related coronavirus case was detected in Illinois, USA [5]. On 9 January 2020 a news outlet reported that laboratory tests on samples from patients found 15 positive results of the new-type coronavirus, and this new-type, SARS- CoV-2, was isolated from one patient’s samples. The laboratory results showed SARS-CoV-2 had caused viral pneumonia in 59 cases [6]. After a brief period, the virus swiftly spread globally causing fear and chaos around the world. According to the Centers for Disease Control and Prevention (CDC), there are Vaccines 2021, 9, 1086. https://doi.org/10.3390/vaccines9101086 https://www.mdpi.com/journal/vaccines