This review has focused on the development of mRNA nano-vaccine and the biochemical interactions of anti-COVID-19 mRNA vaccines with various disease conditions and age groups. It studied five major groups of individuals with different disease conditions and ages, including allergic background, infarction background, adolescent, and adult (youngsters), pregnant women, and elderly. All five groups had been reported to have background-related adverse effects. Allergic background individuals were observed to have higher chances of experiencing allergic reactions and even anaphylaxis. Individuals with an infarction background had a higher risk of vaccine-induced diseases, e.g. pneumonitis and interstitial lung diseases. Pregnant women were seen to suffer from obstetric and gynecological adverse effects after receiving vaccinations. However, interestingly, the elderly individuals (> 65 years old) had experienced milder and less frequent adverse effects compared to the adolescent (<19 and >9 years old) and young adulthood (19-39 years old), or middle adulthood (40-59 years old) age groups, while middle to late adolescent (14-17 years old) was the riskiest age group to vaccine-induced cardiovascular manifestations.