Background: In December 2019, many cases were detected in Wuhan, China with flu-like symptoms, and it turned out to be a new version of the coronavirus, namely Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The disease caused by the virus is called COVID-19 and could be life-threatening. The virus spread rapidly from China to the entire world and on March 11, 2020, the World Health Organization (WHO) announced that COVID-19 was a pandemic. Restrictions such as social distancing, masking, hand hygiene and restrictions on social contact were put in place to reduce the spread of the virus. But the only effective way to control the pandemic was through vaccination.

Purpose: This work aimed to compare two vaccines AstraZeneca AZD1222 and Sinopharm BBIBP-CorV approved by the World Health Organization against COVID-19 infection, in terms of effectiveness and occurrence of side effects.

Method: This literature study is based on searches in the database PubMed. Relevant articles including randomized clinical and retrospective cohort studies were selected between 2020 and 2023. By compiling and analysing the data from the included articles, conclusions could be drawn about the effectiveness of the two vaccines and the occurrence of side effects.

Results: AZD1222 had an overall efficacy of 74.0% in the 18-64 age group, 83.5% efficacy in the age group ≥ 65, and 94.2% efficacy against COVID-19-related hospitalization. The efficacy of BBIBP-CorV in preventing symptomatic COVID-19 infections was 78.1%, 90.2% against hospitalization with 96.4% efficacy in working age and 53.3% efficacy in those older than 60 years. Both vaccines showed good safety without serious side effects. Adverse events were mild to moderate and greater after the first dose of both vaccines. The most common side effects were pain at the injection site, headache, and fever. The number and duration of adverse events were greater with AstraZeneca AZD1222 than Sinopharm BBIBP-CorV. 

Discussion: Both vaccines were shown to be effective and safe. There was no significant difference in efficacy between the two vaccines, and both showed an overall efficacy of over 70% against COVID-19 infection and an efficacy of over 90% against hospitalization. However, AZD1222 showed greater efficacy in older subjects while Sinopharm showed greater efficacy in younger subjects. BBIBP-CorV was found to be slightly safer with fewer side effects and shorter duration compared to AZD1222. An accurate and reliable comparison of two COVID-19 vaccines, especially regarding their effectiveness, is challenging to ensure due to several factors such as study methods, study populations, geographic areas, age groups, and participant characteristics that differed in the selected articles. So further studies are needed to confirm the results.