Immunogenicity and Safety of Concomitant Administration of 23-valent Pneumococcal Polysaccharide Vaccine and Trivalent Inactivated Inuenza Vaccine in Adults Aged 50-70 Years

Background To explore the serological protective effect and to evaluate the safety after combined immunization with 23-valent pneumococcal polysaccharide vaccine and trivalent inactivated inuenza vaccine in adults aged 50-70 years. Methods This trial was designed as a single-center, randomized, single-blind, and positive parallel control vaccination study. A total of 1,065 people aged 50-70 years old were observed in Zhenjiang city, Jiangsu Province. Three groups were established, namely, the combined vaccine group (366 people), the pneumonia vaccine group (363 people) and the inuenza vaccine group (364 people). The subjects were randomly assigned to each group. Results A total of 1065 subjects were recruited. The noninferiority criterion of GMC ratios was met for all 7 pneumococcal serotypes after concomitant administration when compared with the administration of PPV23 alone. After concomitant administration, the noninferiority criterion of seroconversion rates was met for all in ﬂ uenza subtypes except the in ﬂ uenza H3 virus. The overall incidence of systemic adverse events was 6.67% (71/1065). The most frequently reported systemic adverse events were abnormal body temperature, muscle aches, nausea, and diarrhea. No statistically signicant difference in systemic adverse events was found among the three groups. Conclusion The local and systemic response rates in the combination group, pneumonia group and inuenza group were similar to those of many similar vaccines, suggesting that the vaccine has good clinical safety. Serological ndings from the combination vaccine suggest that it should be encouraged in the future to increase vaccination rates for inuenza and pneumonia. vaccine clinical trials Food Injection-site adverse reactions (e.g., redness, adverse reactions and the


Introduction
In uenza is an important contributor to mortality in elderly individuals worldwide. In urban China, during the period 2003-2008, 86% of in uenza-associated deaths occurred among people aged ≥ 65 years [1] . Pneumococcal infections can also cause serious diseases, including meningitis, bacteremia, and pneumonia. Streptococcus pneumoniae is a common causative agent of pneumonia. Older adults, especially those older than 65 years, are thought to be a high-risk population for pneumococcal infections. The case fatality rates (CFRs) can be high, 15-20% among adults and 30-40% among elderly patients, even after appropriate antibiotic therapy and intensive care.
Therefore, the trivalent inactivated in uenza vaccine (TIV) and 23-valent pneumococcal polysaccharide vaccine (PPV23) have been recommended to elderly people in many countries [2,5,6] . However, the coverage of TIV and PPV remains very low. Concomitant administration of TIV and PPV23 is considered one of the most effective ways to improve immunization coverage. To date, there have been some studies on the incidence of related diseases after pneumococcal polysaccharide vaccine and in uenza vaccine combined, with reported improvements in respiratory symptoms. Studies on concomitant administration of TIV and PPV23 are still very limited [4][5][6][7] . This study intends to evaluate the immunogenicity and safety of PPV23 and in uenza virus split vaccine (TIV) at the same time in 50-to 70-year-old individuals and to provide a basis for the development of immunization strategies to prevent Streptococcus pneumoniae and seasonal in uenza viral infections in elderly individuals.
Methods And Methods

Study Design and participants
This randomized, controlled, open-label study evaluated the safety and immunogenicity of PPV23 and TIV administered to healthy people as well as those with stable underlying diseases (≥ 8 weeks) who were older than 50 years. The exclusion criteria were as follows: (1) a history of pneumonia in the previous 5 years, (2) previous pneumococcal vaccination in the past 5 years, and (3) previous in uenza vaccination in the past year. Individuals with any known vaccine component allergies, any other vaccination or immunoglobulins within the previous 4 weeks, or a history of fever (axillary temperature ≥ 38℃) within the previous 3 days were excluded. All the participants included were randomized in a 1:1:1 ratio into 3 groups: those receiving one dose of trivalent inactivated split-virus in uenza vaccine (TIV, Group 1, 352 people); those receiving one dose of 23-valent pneumococcal polysaccharide vaccine (PPV23, Group 2, 353 people); and those concomitantly receiving one dose of split-virus in uenza vaccine and 23-valent pneumococcal polysaccharide vaccine in different arms (TIV + PPV23, Group 3, 360 people) (see Fig. 1). The primary objective of the study was to demonstrate the differences in immune responses to in uenza antigens or PPV23 serotypes 1 month after vaccination in the PPV + TIV group (concomitant administration) compared to those in the TIV group and PPV group separately. The secondary objective of the study was to assess the safety of concomitant administration in the PPV + TIV group.

Procedures
Blood samples (4 mL) were collected before the rst administration (day 0) and at day 28 for immunogenicity evaluation. After centrifugation, the serum was frozen at -20 °C until being sent to laboratories for serological testing. The immune responses to the three antigens in the in uenza vaccine were measured by using a standard hemagglutination inhibition (HI) assay. Seven pneumoniae

Statistics analysis
The mean geometric titers (GMT g/ml) of serum antibodies before and 1 month after immunization with PPV23 were calculated. The TIV positive conversion rate is de ned as the proportion of those who were negative before GMC immunization and increased 1:40 or more after immunization or ≥ 4 times after immunization. The cut-off value of the immunogenicity noninferiority evaluation of the seven serotypes of pneumococcus in the combined group was 0.5, and the cut-off value of the noninferiority e ciency of the three serotypes of in uenza was − 10%. Quantitative data were calculated using a t test or an analysis of variance, and data that did not meet normality were tested using the Wilcoxon rank-sum test. The classi cation data were analyzed by the χ 2 -test or Fisher's exact probability method, and P < 0.05 was considered statistically signi cant. All statistical analyses were performed using R3.5.1 software.

Baseline characteristics
A total of 1065 subjects were recruited. The participants were randomly assigned in a 1:1:1 ratio into one of three vaccination groups: PPV + TIV (N = 360), PPV (N = 353) and TIV (N = 352). Baseline demographics were similar among the study groups (see Table 1). Studies have already shown that the antibody GMC of the corresponding type of pneumonia was higher than that before immunization when PPV was administered alone.
Baseline GMCs of every serotype were not distinguishable between the PPV group and the PPV + TIV group (see Table 2). After PPV23 vaccination, GMCs increased markedly irrespective of concomitant administration of TIV. Overall, the comparison of geometric mean concentrations after 23-valent pneumococcal conjugate vaccine (PPV23) administration between the PPV group and the PPV + TIV group showed no signi cant differences (see Table 2). Consequently, the noninferiority criterion of GMC ratios was met for all 7 pneumococcal serotypes after concomitant administration when compared with the administration of PPV23 alone.  Tables 3 and 4).

Safety
Approximately 85 of 1065 participants were reported to have adverse events. The majority of adverse events were mild. The overall incidence of local adverse events was 1.31% (14/1065). The most common local reactions were pain at the injection site, cough and swelling. Pain was more common in the TIV group (1.57% vs. 0.69% for the PPV + TIV group and 0.29% for the PPV group, P < 0.001).
The overall incidence of systemic adverse events was 6.67% (71/1065). The most frequently reported systemic adverse events were abnormal body temperature, muscle aches, nausea, and diarrhea. No statistically signi cant difference in systemic adverse events was found among the three groups.
The incidence of adverse reactions in the adult group was 34.00% (85 persons), the incidence of grade 1 adverse reactions was 30.00% (75 persons), and the incidence of grade 2 adverse reactions was 3.60% (9 persons); grade 1 adverse reactions accounted for 88.24% (75/85), and grade 2 adverse reactions accounted for 10.59% (9/85) of the total number of reactions. In addition, a grade 3 adverse reaction occurred in the adult group (see Table 5).

Discussion
The annual in uenza epidemic causes millions of cases of severe illness and thousands of deaths worldwide [2]. Moreover, in uenza is considered to be an important factor in high winter rates of pneumococcal pneumonia during nonpandemic periods in some studies [10][11][12], showing the advantage of simultaneously preventing pneumococcal infections and in uenza. Vaccination is the most effective strategy to prevent both in uenza and pneumococcal infections. Unfortunately, even several years after these vaccines are licensed for humans, the coverage rates are still not high. In China, the pneumococcal vaccine coverage rate in older adults is approximately 1%. Even in some resource-rich countries, pneumococcal vaccine coverage rates are also relatively low, with rates of approximately 20-40%. Considering the low vaccine coverage rates, concomitant in uenza and pneumococcal vaccination has been recommended as an effective measure to increase pneumococcal vaccine coverage in both children and elderly individuals. In this study, immunogenicity results showed that immune responses for TIV antigens after the concomitant administration of PPV23 and TIV to elderly individuals are robust and noninferior to immune responses after TIV given separately. In addition, there were no statistically signi cant differences for any of the seven serotypes in GMCs after concomitant administration of PPV23 and TIV compared with the administration of PPV23.
Similarly, in some foreign countries, studies have shown that concomitant administration of in uenza vaccine and PPV23/PCV13 resulted in acceptable immunogenicity and safety when compared to either agent given alone [4,5,7,13]. A randomized, controlled trial in the United States found that the anti-pneumococcal IgG responses were statistically signi cantly lower for 8 of 13 serotypes after concomitant administration of PCV13 and TIV than after the administration of PCV13 alone [4]. A retrospective study conducted by Japanese scientists found that, compared with people who received only the in uenza vaccine, those who received a coadministration of pneumococcal and in uenza vaccines had lower the rates of respiratory infections [14]. For adults, especially those aged ≥ 65 years, studies in both Italy and Sweden supported the e cacy of concomitant administration [15,16]. A study in Italy suggested that the administration of in uenza and pneumococcal vaccines leads to substantial health bene ts and to a reduction in mortality [15]. The prospective study in Sweden also showed that rates of hospitalization declined and mortality decreased in the vaccinated cohort [16].
Concomitant vaccination had no additive effects on adverse events in this study. A study from South Korea showed that, compared with the TIV group, local adverse reactions and some systemic adverse events were more common in the PPV group or the PPV + TIV group [7,17].
Our analysis is subject to several limitations. First, the period of observation was not long enough because it was limited to one in uenza season. However, our sample size could counteract this limitation to some degree. Second, we did not consider whether there was any difference in results based on different injection sites. Some previous studies have performed research on this topic but found no difference.
In conclusion, concomitant administration of PPV23 and TIV did not show signi cant interference in antibody responses and demonstrated good safety pro les. Although the defects of the current vaccines cannot be ignored, biomedical research on vaccines will enable many individuals to live longer, more comfortable lives. In addition, it will help to avoid draining health resources and straining the social welfare system.

Conclusions
Overall, The local and systemic response rates in the combination group, pneumonia group and in uenza group were similar to those of many similar vaccines, suggesting that the vaccine has good clinical safety.
List Of Abbreviations

Consent for publication
Not applicable.

Availability of data and materials
The data used and analyzed for the current study is available upon request from the rst author Yuanbao Liu (E-mail: 94724252@qq.com).

Competing interests
Not applicable.

Supplementary Files
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