Table 1.

Descriptive information on the four approved COVID-19 vaccines.

Parameters	AstraZeneca [12,25,34]	Pfizer [15,22,30,32]	Moderna [11,21,32,35]	Janssen [8,36,39]
Vaccine type	Vector-based	RNA-based	RNA-based	Vector-based
Manufacturing country	UK	US	US	The Netherlands/US
Dose	0.5 mL	0.3 mL	0.5 mL	0.5 mL
Number of dose and suggested duration between them *	2 (28 days)	2 (21 days)	2 (28 days)	Single dose
Route of administration	Intra-muscular (Preferably deltoid muscle)	Intra-muscular (Preferably deltoid muscle)	Intra-muscular (Preferably deltoid muscle)	Intra-muscular (Preferably deltoid muscle)
Mechanism of action	Adenovirus is used as a vector to carry the genetic code for making viral spike protein by host cells, triggering antibody production.	m-RNA induces the host cell to produce spike proteins, triggering the production of immune cells.	m-RNA induces the host cell to produce spike proteins, triggering the production of immune cells.	Adenovirus is used as a vector to carry the genetic code for making viral spike protein by host cells, triggering antibody production.
Protection post-vaccination	Significant antibody levels can be seen after 14 days	Significant antibody level in blood after 14 days	Significant antibody level in blood after 14 days	Significant antibody level in blood after 14 days
High risk participants	Patients suffering from cardiovascular, respiratory, metabolic, hepatic, renal, haematological and immunocompromised conditions
Storage temperature	2 to 8 °C	−20 to −70 °C	2 to 8 °C	2 to 8 °C
Specific adverse events	Thrombosis, Anaphylaxis	Lymphadenopathy, Myocarditis	Cholecystitis, Myocardial infarction	Hypersensitivity, Appendicitis
Precautions	Pregnancy, lactation, less than 18 years, severe illness and allergic to vaccine components

* Recent reports suggest that increasing the gap between two doses enhances efficacy.