BACKGROUND: Emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections and the resultant disease, coronavirus disease 2019 (COVID-19) led the world into a pandemic with over 90 million cases and 2 million deaths. While the symptoms are still under study, most exposed individuals experience mild infection but those with chronic condition and advance age develop severe illness.

OBJECTIVES: To systematically review and determine the immunogenicity and safety of COVID-19 vaccines compared with control groups in the healthy adults.

METHODS: A systematic literature search was conducted in PubMed, Medline, Embase and Cochrane up to January 2021. Randomized controlled trials assessing the immunogenicity of any dose of COVID-19 vaccine in adults by anti-SARS-CoV-2 IgG antibodies GMT and neutralizing antibodies GMT response at 28 days post-immunization were considered for inclusion. Groups at day 28 with the highest GMT were further examined for their adverse events.

RESULTS: Of 139 studies identified, nine were included. Nine studies reported data on eight vaccines (ad5-vectored COVID-19, BBIBP-CorV, BNT162b1, BNT162b2, ChAdOx1 nCoV-19, CoronaVac, rSARS-CoV-2, and WIV04 Strain) with 4205 subjects mean age ranging between 30.8 - 69.7 years, consisting of 52.46% females. 9/9 studies reported GMT titers at 28 days post vaccination compared with placebo/comparator and 6/9 studies reported seroconversion rates.

All eight vaccines noted adverse events ranging from mild to severe, no study reported vaccine related hospitalization. Local reactions (such as redness, pain and swelling) at the injection site and systematic reactions (such as chills fatigue, fever, and headache) were commonly noted among vaccine recipients. Overall, subjects in the control arm experienced local and systemic reactions less frequently compared to experimental arm.

CONCLUSIONS: All eight vaccines elicit an immune response above specified threshold among adults compared with control groups, while maintaining reasonable safety profiles.