Table 1.

Characteristics of the Principal Covid-19 Vaccines

	Pfizer/BioNTtech	Moderna	Astra – Zeneca Oxford	Janssen Johnson & Johnson
Mechanism of action	mRNA	mRNA	Adenovirus Viral vector (Replication deficient chimpanzee adenovirus)	Adenovirus Viral vector (Replication -incompetent human Adenovirus serotype 26)
Antigen	Full – length spike protein	Full - length spike protein	Spike protein	Spike protein
Doses	2 doses 21 days apart	2 doses 28 days apart	2 doses 12 weeks apart	Only 1 dose
Side effects	Rare allergies and anaphylaxis	Rare facial paralysis (Bell’s Palsy)	Rare thromboembolic events, rare cases of blood-clots, pulmonary embolism, thrombocytopenia	Rare cases of blood clots, thrombocytopenia, Guillain-Barré Syndrome
Overall efficacy	95% for disease 87.5% for severe disease	94% for disease 100% for severe disease	70% (64% after 1 dose) (70.4% after 2 doses)	72% in the USA 66% in Latin America 57% in South Africa
Storage Temperature	− 70 °C 2–8 °C for 5 days	− 20 °C 2–8 °C for 30 days	2–7 °C for 6 months	2–8 °C for 3 months