SARS-CoV-2 variants and vaccines: Efficacy, side effects and clinical evidences

The global challenge posed by the SARS-CoV-2 pandemic has been unprecedented due to the rapid evolution of the virus, resulting in the emergence of variants that complicate control measures.The presented review offers a thorough examination of the relationship between SARS-CoV-2 variants and the effectiveness of vaccines, as well as a detailed evaluation of vaccine safety.The analysis focuses on significant variants such as Alpha, Beta, Gamma, Delta, and Omicron, each characterized by specific mutations that contribute to increased transmissibility, immune evasion, or pathogenicity.Of particular, mutations like D614G and more than 30 alterations in the spike protein observed in Omicron.Initially, various vaccine technologies, including mRNA and inactivated virus platforms, demonstrated considerable efficacy (60-90%) against early virus strains.However, the effectiveness of vaccines has been notably reduced against symptomatic infection with variants like Beta and Omicron.This decline is supported by real-world data, for example, the Pfizer-BioNTech vaccine showed a decrease in efficacy from 89.5% against Alpha to 75% against Beta.Despite this decline, the vaccines continue to provide robust protection (over 90%) against severe disease, even with the Omicron variant.Extensive clinical trials and post-market surveillance have consistently reaffirmed the safety of vaccines.Mild side effects are commonly reported, while severe adverse events are uncommon.For instance, thrombosis with thrombocytopenia syndrome occurs in 1-7 cases per million doses of adenoviral vector vaccines.Despite these isolated incidents, overwhelming evidence supports the conclusion that the advantages of vaccination far surpass the associated risks.This review consolidates the current understanding of SARS-CoV-2 variants, vaccine effectiveness against these variants, and the safety profiles of the vaccines.It offers crucial insights for healthcare professionals and policymakers to effectively manage the changing landscape of the ongoing pandemic.