International Journal of Clinical Case Reports 2024, Vol.14, No.3, 117-131 http://medscipublisher.com/index.php/ijccr 121 tolerability profile, even one year after vaccination (Alberer et al., 2017). These findings suggest that mRNA vaccines have a favorable long-term safety profile, although continued monitoring is essential. 4.3 Safety in special populations The safety of mRNA vaccines in special populations, such as immunocompromised individuals, has been a focus of recent research. A study investigating the BNT162b2 vaccine in five groups of immunocompromised patients found that the vaccine was generally safe, although the rate of seroconversion was substantially lower than in healthy controls (Figure 2). The study highlighted the need for additional vaccine doses in certain immunocompromised patient groups to improve immunity (Bergman et al., 2021). Another study on the mRNA-1273 vaccine included participants at high risk for SARS-CoV-2 infection or its complications. The vaccine showed 94.1% efficacy at preventing COVID-19 illness, including severe disease, with no safety concerns identified (Baden et al., 2020). Figure 2 Comparison of Seroconversion and Antibody Response Post SARS-CoV-2 Vaccination in Different Immunocompromised States (Adapted from Bergman et al., 2021) Image Description: (a) Shows the seroconversion rates, defined as antibody titers ≥0.8 U/ml, in five immunocompromised groups and the control group post-vaccination.; (b) Shows the median SARS-CoV-2-specific antibody titers in the five immunocompromised groups and the control group.; (c) Shows the median (95% confidence interval) SARS-CoV-2-specific antibody titers in individuals who seroconverted by day 35.; (d) Displays individual antibody dynamics (black thin lines) and median interquartile range (IQR) (colored thick lines) for each group (Adapted from Bergman et al., 2021) Bergman et al. (2021) studied the seroconversion and antibody titers in different immunocompromised patient groups and healthy controls. The study indicated that the seroconversion rate and antibody titers post-vaccination were significantly higher in the healthy control group compared to the immunocompromised groups. Among the immunocompromised patients, those in the HIV and HSCT/CAR-T groups showed more notable antibody responses, while the SOT and CLL groups exhibited weaker responses. These results highlight the differential responses to vaccination among immunocompromised patients, suggesting the need for personalized vaccination strategies to enhance protection in these high-risk populations. In children aged 5 to 11 years, a systematic study and meta-analysis found that mRNA COVID-19 vaccines were associated with lower risks of SARS-CoV-2 infections and severe COVID-19-related illnesses. Most vaccinated children experienced at least one local adverse event, but severe adverse events were rare and resolved within
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