Page 21 - JCTR-11-3

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

and potential for serious complications, it remains an immunogenicity of subunit IVs is limited, further studies
important public health concern globally. Most patients are necessary to rationally promote and administer
1
can recover within a week; however, influenza viral subunit IVs. A commonly used method to assess the
infection can be particularly severe for the elderly, children, immunogenicity and safety of subunit IVs is to conduct
pregnant women, and immunocompromised individuals. statistical analysis by combining data from previous
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With the global outbreak of the COVID-19 pandemic, relevant studies. This can be achieved through systematic
public attention and demand for vaccine administration and meta-analysis. By assessing indicators, such as
have been increasing. In addition to the hazards caused by geometric mean titers (GMTs), serum protection rates,
the COVID-19 virus, people have also started focusing on seropositivity rates, and adverse events among participants
the transmission and control of other respiratory diseases, who received subunit IVs, we can compare the reliability
particularly influenza. of non-adjuvanted subunit IVs, adjuvanted subunit IVs,
Vaccine immunization is considered a highly effective and split vaccines. The present study aims to provide
measure for preventing influenza and reducing its useful information for IV vaccination strategies, thereby
impact on individuals and communities. In China, the guiding the promotion and use of IVs and increasing
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currently recommended groups for influenza vaccine vaccination rates.
(IV) administration include individuals aged 65 years and 2. Methods
above, children and adolescents aged 6 months and above,
pregnant women, individuals with chronic diseases, such as All methodological procedures in this study strictly
heart disease, diabetes, and respiratory diseases, healthcare adhered to the Meta-analysis of Observational Studies in
workers, other high-risk occupational workers, as well Epidemiology reporting guidelines as shown in section S1
as individuals who frequently come into contact with in the Supplementary File.
large crowds, such as students, teachers, service industry
workers, and other high-risk groups. The Advisory 2.1. Search strategy
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Committee on Immunization Practices advises IV for all An extensive retrieval of relevant references was performed
individuals 6 months or older with no contraindications. in electronic databases from August 1, 2013, to August
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The influenza virus undergoes rapid mutations, and the 31, 2024. A cross-checking process was then employed to
effectiveness of the vaccine diminishes over time. Therefore, determine the studies that met the specified criteria. The
the vaccine formulation is updated annually based on databases searched included PubMed, Cochrane, and
recommendations from the World Health Organization EMBASE. The search terms employed were “influenza,”
and the Committee for Medicinal Products for Human Use “vaccine,” “immunogenicity,” and “safety.” The entire query
in the European Union. At present, IVs include inactivated phrases for each database can be found in “S2. Search
whole virus vaccines, split virus IVs, subunit vaccines, strategy” in the Supplementary File. Furthermore, additional
virus-like particle vaccines, live attenuated vaccines, and studies were identified by manual screening of the reference
recombinant virus vector vaccines. In China, the approved lists of relevant systematic reviews and meta-analyses.
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IVs mainly include split virus vaccines, subunit vaccines,
and live attenuated vaccines. 8 2.2. Inclusion and exclusion criteria
Vaccine safety assessment is crucial to ensure that As shown in Figure 1, the inclusion criteria were as
individuals can confidently receive vaccines with follows: (i) clinical or retrospective studies investigating
minimal risk. Subunit IVs only contain highly purified the immunogenicity, efficacy, or safety of IVs, including
hemagglutinin (HA) and neuraminidase components. those with subunit IVs; (ii) participants consistently
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Clinical studies have demonstrated that subunit IVs have administered with the same IV type during the entire
better safety profiles compared to whole virus IVs and split intervention process; (iii) participants belonging to a
virus IVs, especially when administered with adjuvant to healthy population; and (iv) full-text articles published in
enhance immunogenicity. Our analysis also considers English to provide comprehensive clinical information.
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the incidence and severity of adverse reactions following The exclusion criteria included: (i) study populations
vaccination with subunit IVs compared to split virus involving non-healthy individuals; (ii) studies that do not
IVs. Through systematic evaluation of data from various specify the type of vaccine used; (iii) studies that do not
studies, we assess the overall safety of these vaccines and involve subunit IVs; (iv) duplicate publications; (v) other
identify potential serious adverse events that may occur. publications, including letters, comments, case reports, and
The split IV is currently the most commonly used editorials; (vi) non-English papers; and (vii) investigations
IV in China. Although research on the safety and without completed datasets.
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Volume 11 Issue 3 (2025) 15 doi: 10.36922/JCTR025060006