Page 40 - JCTR-11-3

Journal of Clinical and
Translational Research Immunogenicity and safety of flu vaccines

of IVs is still ongoing, and current research results are not The sustained presence of antibodies over a long-term
yet conclusive. serves as a crucial marker for immunogenicity; however,
The incidence of adverse events is a crucial indicator for investigation in this area is still remarkably limited in
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assessing the safety of IVs. Subunit IVs, which enhance subsequent studies of GMTs and seroconversion. In
addition, the seasonal impact of influenza strains is another
the purity of effective antigens compared to split IVs, are
expected to provide increased safety. However, our significant factor. Despite the comprehensive nature of
9,25
systematic review revealed that the incidence of adverse our search protocol and the use of extensive search terms,
reaction events in most adjuvanted subunit IVs was higher some relevant studies may have been overlooked.
than that in split IVs. This may be due to the additional 5. Conclusion
side effects associated with adjuvants, which are consistent
with previous studies. We further compared the impact This study indicated that adjuvanted subunit IVs, non-
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of adjuvant addition on the safety of subunit IVs and adjuvanted IVs, and split IVs demonstrated strong
bolstered this viewpoint. The incidence of adverse events performance in terms of immunogenicity. The use of
from adjuvanted subunit IVs was significantly higher than adjuvanted subunit IVs can enhance immunogenicity, but
that from non-adjuvanted subunit IVs. However, most the addition of adjuvants may increase the occurrence of
studies did not extensively address the severity of adverse adverse events. In contrast, split IVs and non-adjuvanted
events, necessitating further research to confirm this subunit IVs exhibit comparable levels of protective capacity
point. In some studies of non-adjuvanted subunit IVs, we and immunogenicity. Therefore, for the majority of the
found that they may offer greater safety. However, relative population, it is recommended to use non-adjuvanted
to adjuvanted subunit IVs, the immunogenicity of non- subunit IVs to ensure better safety. For populations with
adjuvanted subunit IVs may be slightly reduced, although weaker immune responses, the use of adjuvanted IVs is
still comparable to that of split IVs. Therefore, for the recommended to provide enhanced immunogenicity.
majority of the population, non-adjuvanted subunit IVs However, it is essential to highlight that the quantity and
should be prioritized when receiving the IV to minimize quality of the included studies are limited at present; further
the risk of adverse reaction events. Adjuvanted subunit IVs high-quality research is necessary to validate these results
are recommended for populations with lower immune and ensure their accuracy and reliability. Furthermore, due
capability. Nevertheless, when formulating vaccination to the high variability of influenza virus strains, there is a
plans, individual medical conditions and recommendations need for more research on the effects of repeated influenza
should still be considered comprehensively. vaccination and the long-term protective efficacy of IVs.
This research direction is crucial for improving vaccination
This is the first meta-analysis to compare the strategies and further reducing the spread of influenza.
immunogenicity and safety of non-adjuvanted subunit IVs,
adjuvanted subunit IVs, and split IVs. The study conducted Acknowledgments
a comprehensive analysis by systematically summarizing None.
all clinical research data comparing subunit IVs with
split IVs and adjuvanted subunit IVs, providing a more Funding
comprehensive and intuitive display of the immunogenicity
and safety of IVs. This search was conducted on the most This work was supported by the Fengcheng Talents Plan,
relevant databases, and appropriate measures were taken a part of the 113 Biomedical Special Grant of Taizhou,
to select studies and extract data to prevent potential China.
errors, thus minimizing selection bias. In addition, the Conflict of interest
included studies exhibited minimal risk of bias, allowing
us to consider the evaluation results to be robust. This All authors declare that they have no conflicts of interest.
meta-analysis is based on an extensive search strategy, but
the primary literature has certain limitations. The aim of Author contributions
RCTs is to determine the immunogenicity and safety of Conceptualization: Ze Chen
IVs and not to compare the effectiveness of vaccination Formal analysis: Lei Wang
after exposure. Furthermore, there is still a lack of Investigation: Lei Wang, Dan Li, Hongbo Zhang, Youcai
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research comparing the immunogenicity and safety of An, Xinyue Zhang
non-adjuvanted subunit IVs with adjuvanted IVs, as well Methodology: Lei Wang, Hongbo Zhang, Youcai An,
as non-adjuvanted subunit IVs with split IVs. Variations in Xinyue Zhang
adjuvant dosage have also led to wide confidence intervals. Writing – original draft: Lei Wang, Ze Chen

Volume 11 Issue 3 (2025) 34 doi: 10.36922/JCTR025060006