COVID-19 vaccine: Potential candidates, achievements, and challenges

Severe acute respiratory syndrome [SARS]-CoV-2, which is the causative agent of Coronavirus Disease 2019 [COVID-19] disease, has engulfed more than 2.4 million people and still counting. As this pandemic is at its peak and is responsible for more than 100 million infected people worldwide, there is an urgent need to develop an effective vaccine to stop the COVID-19 disease. More than 220 vaccine candidates are in the pre-development stage while 15 candidates are in the developmental stage, from which Pfizer/BioNTech, Moderna, and some other vaccines have received approval by some countries for emergency use only. Fever, tiredness, headache, joint pain, swelling at the injection site and some other common effects have been found by using these vaccines. Efficacy, rapid mass production, and long-term immunity as well as acceptance of vaccination by society are the main challenges in developing a safe vaccine against COVID-19 despite the fact that some vaccines have over 90% efficiency against COVID-19 and are useful in developing immunity as well.