FormalPara Key Summary Points

Why carry out this study?

Annual influenza vaccinations are recommended for adolescents and adults with moderate to severe asthma.

Tezepelumab is a human monoclonal antibody that blocks the activity of thymic stromal lymphopoietin and is approved as an add-on maintenance treatment for adults and adolescents 12 years and older with severe asthma.

This study investigated the effect of tezepelumab on the humoral immune response to the quadrivalent seasonal influenza vaccine in adolescents and young adults with moderate to severe asthma.

What was learned from the study?

There was no observed suppression of the humoral immune response after influenza vaccination in adolescents and young adults with moderate to severe asthma treated with tezepelumab compared with placebo.

Therefore, the influenza vaccine can be administered to this patient population during tezepelumab treatment.

Introduction

Asthma is a chronic inflammatory disorder of the airways, characterized by widespread airflow obstruction and airway hyperresponsiveness resulting in recurrent episodes of wheezing, breathlessness, and coughing [1, 2]. Epidemiological evidence suggests that asthma in adults and children is a major risk factor for infection with the influenza virus and subsequent hospitalization [3,4,5]. One retrospective study found that asthma was an underlying comorbidity in 44% of children hospitalized owing to influenza during the 2009 influenza pandemic [3]. Patients with asthma may also be more likely to experience influenza-related complications than the general population [3, 6,7,8].

Influenza vaccines have been shown to reduce the number of hospital admissions and likelihood of exacerbations and complications in patients with asthma [9]. A meta-analysis of 35 studies that evaluated influenza vaccine effectiveness in patients with asthma reported that the influenza vaccine prevented 59–78% of asthma exacerbations leading to hospitalization and or emergency department visits [9]. As such, the Global Initiative for Asthma and the US Centers for Disease Control and Prevention recommend annual influenza vaccinations for adolescents and adults with moderate to severe asthma [1, 8].

Tezepelumab is a human monoclonal antibody that binds to thymic stromal lymphopoietin (TSLP), an epithelial cytokine that is implicated in asthma pathophysiology [10,11,12]. In the phase 3 NAVIGATOR (ClinicalTrials.gov identifier: NCT03347279) and phase 2b PATHWAY (ClinicalTrials.gov identifier: NCT02054130) studies, tezepelumab significantly reduced the annualized asthma exacerbation rate and improved lung function, asthma control, and health-related quality of life compared with placebo in patients with severe, uncontrolled asthma [10, 11]. Tezepelumab is approved as an add-on maintenance treatment option for adults and adolescents 12 years and older with severe asthma that remains uncontrolled with standard-of-care therapy (medium- or high-dose inhaled corticosteroids plus a long-acting β2-agonist, with or without oral corticosteroids) [13, 14].

Clinical studies have demonstrated that blocking TSLP inhibits multiple inflammatory pathways, most notably those associated with type 2 inflammation. This includes allergic and eosinophilic inflammation, mediated by T helper 2 cells and innate lymphoid cells [10, 12, 15]. Tezepelumab has also been shown to reduce serum levels of interleukin (IL)-5 and IL-13 in addition to levels of key biomarkers associated with type 2 inflammation, including blood eosinophils, fractional exhaled nitric oxide, and serum total immunoglobulin (Ig) E [10, 11, 16].

Given the effects of tezepelumab on type 2 inflammatory biomarker levels, it is important to assess whether tezepelumab could affect the humoral immune response to the influenza vaccine. The phase 3b VECTOR study was conducted to investigate the effect of tezepelumab treatment on the humoral immune response to the quadrivalent seasonal influenza vaccine in adolescents and young adults with moderate to severe asthma.

Methods

Study Design

VECTOR (ClinicalTrials.gov identifier: NCT05062759) was a randomized, multicenter, double-blind, parallel-group, placebo-controlled study conducted at 15 centers in the USA (Fig. 1). Patient enrollment began on August 23, 2021, and ended on November 18, 2021; the study was completed on July 18, 2022 [17]. The enrollment period was limited so that patient randomization coincided with the 2021–2022 winter influenza vaccination season in the USA.

Fig. 1
figure 1

VECTOR study design. Q4W every 4 weeks, SC subcutaneously

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Eligible patients were adolescents (aged 12–17 years) and young adults (aged 18–21 years) with physician-diagnosed, moderate to severe asthma for at least 12 months before enrollment. The study population was selected on the basis of a similar previous study of an anti-IL-5 biologic [18]. Asthma was confirmed by a postbronchodilator airway reversibility test and a documented history of inhaled corticosteroid and long-acting β2-agonist treatment. Full inclusion and exclusion criteria can be found in Supplementary Table S1.

Patients were randomized 1:1 to receive tezepelumab 210 mg or placebo subcutaneously at weeks 0, 4, 8, and 12. Treatment allocation was stratified by age (adolescents and young adults) to ensure a balanced distribution of tezepelumab and placebo in the two age groups. Patients received a single dose of inactivated quadrivalent seasonal influenza vaccine (FLUCELVAX QUADRIVALENT; Seqirus, Holly Springs, NC, USA [influenza season 2021–2022]) intramuscularly at week 12 before receiving the fourth dose of study treatment. By the time of vaccination, the patients’ serum concentration of tezepelumab would have reached steady state. The vaccine contained the following four strains recommended by the World Health Organization for the influenza season 2021–2022 in the northern hemisphere: influenza A H1N1, influenza A H3N2, influenza B Yamagata lineage, and influenza B Victoria lineage [19].

Serum samples for evaluation of the antibody response to the influenza vaccination were taken at week 12 (prevaccination) to determine baseline antibody concentrations and at week 16 (4 weeks after vaccination) when a fully developed immune antibody response to the vaccination was expected [20]. Patients completed a follow-up end-of-study visit at week 28.

The study was conducted in accordance with the ethical principles of the Declaration of Helsinki, International Council for Harmonisation good clinical practice guidelines, and applicable regulatory requirements. Approvals from the central institutional review board (Advarra, Columbia, MD, USA) and local independent ethics committees were obtained, and all patients or their legal guardians provided written informed consent in accordance with local requirements.

Outcomes

The primary outcome was to evaluate the effect of tezepelumab on the humoral immune response following administration of the quadrivalent seasonal influenza vaccine. Immunogenicity was assessed using vaccine strain-specific hemagglutination inhibition (HAI) and microneutralization (MN) assays. HAI assays measure the ability of serum to block hemagglutination, which is the aggregation of red blood cells caused by the influenza virus [21, 22]. MN assays detect antibodies that directly neutralize the virus by determining the half-maximal inhibitory dilution of each sample [21, 23]. HAI and MN assays were validated and performed by Viroclinics Biosciences, Rotterdam, Netherlands.

The primary outcome measures included: (1) the strain-specific HAI and MN antibody geometric mean fold rises (GMFRs) from immediately before administration of the vaccine (week 12) to 4 weeks postvaccination (week 16); (2) the strain-specific serum HAI and MN antibody geometric mean titers (GMTs) at week 16; (3) the proportion of patients experiencing a strain-specific, postvaccination antibody response at week 16 (defined as a fourfold or larger rise in HAI or MN antibody titer from week 12 to week 16); and (4) the proportion of patients with a strain-specific, postvaccination HAI and MN antibody titer of at least 40 at week 16. The secondary outcomes were the changes from baseline to the end of the study (week 28) in serum trough tezepelumab concentrations and anti-drug antibody (ADA) levels, which were assessed at selected study visits. Safety outcome data were collected, comprising adverse events (AEs) and serious adverse events that occurred at any time from the time of informed consent until the end of the follow-up period.

Statistical Analyses

The statistical analysis of each of the four primary variables was performed separately for each influenza strain and separately for both HAI and MN antibody titers, except for the influenza A H3N2 strain, for which only the MN assay was performed owing to the known low hemagglutination effect of the strain.

The vaccine immunogenicity analysis set was used for the analysis of all primary outcomes. This analysis set included all randomized patients who received the influenza vaccine plus at least one dose of tezepelumab or placebo, had pre- and postvaccination HAI or MN antibody measurements, had no influenza infection before week 16, and had no significant protocol deviations. The safety analysis set included all patients who received at least one dose of tezepelumab or placebo. The pharmacokinetic (PK) analysis set comprised all patients who received tezepelumab and had at least one PK blood sample after the first dose with quantifiable serum concentrations of tezepelumab.

A preplanned sensitivity analysis was performed to assess the robustness of the primary endpoint analysis. This analysis excluded two patients who only had one dose of the study drug at week 0 or who had a previous influenza vaccination in the 6 months before randomization. Two post hoc sensitivity analyses were also conducted. The first analysis assessed whether the small numerical imbalance in baseline body mass index between the tezepelumab and placebo groups influenced the primary endpoint analysis. The second analysis was conducted to assess the impact of anomalous PK data from a single study site.

Descriptive statistics including the geometric standard deviation and the geometric coefficient of variation were used to summarize the antibody endpoints (GMFRs and GMTs). Least-squares geometric mean ratios of GMFRs and GMTs between treatment groups were calculated via an analysis of covariance model, adjusting for treatment group and age group (adolescents or young adults). The proportions of patients who achieved at least a fourfold rise in postvaccination antibody titer from prevaccination (week 12) to week 16 and those who achieved a postvaccination HAI or MN antibody titer of at least 40 at week 16 (end of treatment) were calculated. Corresponding 90% Clopper–Pearson exact confidence intervals were summarized by treatment group and by assay.

All safety outcomes were summarized descriptively. The sensitivity analyses employed the same statistical analyses as stated above.

No formal statistical hypotheses were tested in this study and no adjustment of multiplicity was performed.

Results

Patient Population and Baseline Characteristics

Of the 81 patients enrolled and screened for inclusion in the study, 70 were randomized. Of these 70 patients, 35 were randomized to tezepelumab and 35 to placebo (full analysis set) (Fig. 2). Eleven patients were excluded at screening because they did not meet study participation criteria. The target study population size of 100 randomized patients was not achieved because of recruitment challenges. These included slow site initiation, a short recruitment period due to the influenza season, and issues with supply of the influenza vaccine for use in clinical trials during the ongoing coronavirus disease 2019 (COVID-19) pandemic. This resulted in the vaccine only being available in October 2021, after the start of the vaccination season. Consequently, certain sites did not participate in the study because physicians did not want to delay influenza vaccination to October or November during the COVID-19 pandemic. Because this is a descriptive study and no formal hypothesis testing was planned, the analyses were continued with the available data. This was to avoid continuing into the next influenza season and using a vaccine that contained different viral strains to the current season.

Fig. 2
figure 2

CONSORT diagram. aThe vaccine immunogenicity analysis set comprised all randomized patients who received the influenza vaccine plus at least one dose of tezepelumab or placebo, had pre- and postvaccination HAI or MN antibody measurements, had no influenza infection before week 16, and had no significant protocol deviations. HAI hemagglutination inhibition, MN microneutralization, Q4W every 4 weeks

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A total of 66 patients were included in the vaccine immunogenicity analysis set (tezepelumab, n = 33; placebo, n = 33). Two patients (5.7%) in each treatment group were excluded from this analysis set because they did not receive an influenza vaccine (tezepelumab, n = 1; placebo, n = 1), had an influenza virus infection before week 16 (placebo, n = 1), or had no serum sample for antibodies before the influenza vaccine was administered at week 12 (tezepelumab, n = 1). Overall, 12 patients (17.1%) experienced at least one important protocol deviation: eight patients (22.9%) in the tezepelumab group and four patients (11.4%) in the placebo group.

Baseline demographics and clinical characteristics were similar between treatment groups and were typical of the target population (Table 1). The mean (standard deviation) age was 16.5 (3.0) years and 64.3% of patients (n = 45) were male. Of the randomized patients, 43 (61.4%) were adolescents and 27 (38.6%) were young adults.

Table 1 Baseline demographics and clinical characteristics (full analysis set)
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Primary Outcomes

At week 16 (4 weeks postvaccination), the influenza strain-specific antibody responses measured by HAI and MN assays were generally similar between the tezepelumab (n = 33) and placebo (n = 33) groups. The GMTs and GMFRs at week 16 varied across influenza strains and assays but were generally similar between treatment groups (Tables 2, 3, and Fig. 3). However, for the influenza A H1N1 strain in the HAI assay, the geometric least-squares mean ratio for the GMFR at week 16 demonstrated a greater immune response in the tezepelumab group than in the placebo group (Fig. 3).

Table 2 Influenza strain-specific antibody response assessed by hemagglutination inhibition assays (vaccine immunogenicity analysis set)
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Table 3 Influenza strain-specific antibody response assessed by microneutralization assays (vaccine immunogenicity analysis set)
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Fig. 3
figure 3

Geometric mean ratios (placebo/tezepelumab) of influenza strain-specific antibody responses assessed by hemagglutination inhibition assays (A) and microneutralization assays (B) in the vaccine immunogenicity analysis set. Error bars represent 90% CIs. The hemagglutination inhibition assay was not performed for the influenza A H3N2 strain owing to the known low hemagglutination effect. CI confidence interval, GMFR geometric mean fold rise, GMT geometric mean titer, LS least-squares

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Across the influenza strains, the proportions of patients with an influenza strain-specific antibody titer increase of at least fourfold from week 12 to week 16 were generally similar between treatment groups for both the HAI and MN assays (Tables 2 and 3). However, for the influenza A H1N1 strain in the HAI assay, the proportion of patients with an antibody titer increase of at least fourfold from week 12 to week 16 was numerically higher in the tezepelumab group (78.8%) than in the placebo group (51.5%). The proportions of patients with an antibody titer of at least 40 at week 16 were comparable between treatment groups across the influenza strains for both the HAI and MN assays.

All three sensitivity analyses demonstrated comparable results to the primary analysis and did not affect the study conclusions (Supplementary Tables S2–S5).

Pharmacokinetics and Immunogenicity

The PK analysis set comprised a total of 32 patients who were treated with tezepelumab and had at least one PK sample after the first dose with quantifiable serum concentrations of tezepelumab. After administration, the mean serum trough concentration of tezepelumab increased over time, approaching steady state by week 12 (Fig. 4); the lower limit of quantification was 0.010 µg/mL. At week 12, serum concentrations of tezepelumab were quantifiable in all 30 patients in the tezepelumab group who had reported results at the visit, with a geometric mean value of 27.01 µg/mL (54.21% coefficient of variation). At week 16 (4 weeks postvaccination), the geometric mean serum concentration of tezepelumab was 20.77 µg/mL (369.69% coefficient of variation).

Fig. 4
figure 4

Arithmetic mean (SD) serum trough concentrations of tezepelumab (PK analysis set). PK pharmacokinetic, SD standard deviation

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There were no ADA-positive patients in the tezepelumab group; however, ADA prevalence was 11.4% in the placebo group (4/35 patients; median titer [min, max], 134.4 [67.2, 268.8]).

Safety

Overall, 21 patients (60%) in each treatment group experienced at least one AE (Table 4). Most patients had AEs that were mild (tezepelumab, n = 11 [31.4%]; placebo, n = 12 [34.3%]) or moderate (tezepelumab, n = 10 [28.6%]; placebo, n = 8 [22.9%]) in severity. The most common AE reported was COVID-19 (n = 8 [22.9%] in each treatment group). There was one patient in the placebo group with a serious adverse event with the outcome of death as a result of an event unrelated to the trial. There were no AEs leading to discontinuation of study treatment.

Table 4 AEs during the on-study period (safety analysis set)
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Discussion

Influenza vaccinations are recommended for adolescents and adults with moderate to severe asthma because they can reduce the risk of asthma exacerbations and significantly decrease the numbers of influenza-related outpatient physician visits and hospitalizations [9, 24, 25]. However, there are limited data on the clinical or serological effect of vaccination in patients with asthma and the effects of asthma treatments on the immune response to vaccination [26].

In phase 2b and phase 3 clinical studies of tezepelumab, there were no observed changes from baseline in serum levels of IgA, IgG, or IgM [13], all of which may be generated in response to the influenza vaccine [27]. Serum total levels of IgG were sporadically reduced after administration of tezepelumab in a preclinical study involving cynomolgus monkeys; however, this effect occurred at supratherapeutic concentrations and was not considered adverse [13]. Taking these findings into consideration, it was important to assess whether treatment with tezepelumab impacts the immune response to the influenza vaccine.

Overall, the results from the VECTOR study show that, compared with placebo, tezepelumab did not suppress the humoral immune response after seasonal influenza vaccination in adolescents and young adults with moderate to severe asthma. The influenza strain-specific antibody responses measured by HAI and MN assays were generally similar between the tezepelumab and placebo groups, regardless of differences in the prevaccination GMT, which were likely due to baseline variability in patient characteristics. These characteristics may include exposure to specific influenza strains through previous infection and the number of influenza vaccinations an individual has previously received across multiple seasons, which can both have an impact on prevaccination GMT [28,29,30]. The proportions of patients with an influenza strain-specific antibody rise of at least fourfold from week 12 to week 16 were generally similar between treatment groups in both the HAI and MN assays. For the influenza A H1N1 strain in the HAI assay, the geometric mean ratio for the GMFR at week 16 demonstrated a greater immune response in the tezepelumab group than in the placebo group. However, no difference between treatment groups was observed for the MN GMFR, or the absolute HAI or MN GMT for the influenza A H1N1 strain at week 16. Thus, the difference between treatment groups indicated by the HAI GMFR for the influenza A H1N1 strain is considered a chance finding that may be explained by the small number of patients included in the study.

The findings of this study are largely consistent with other studies that assessed the impact of severe asthma biologics on vaccination response and effectiveness. Zeitlin et al. conducted a study that evaluated the short-term vaccine response in adolescents and young adults with moderate to severe asthma treated with benralizumab. They found that benralizumab did not impair the antibody response to seasonal influenza vaccination [18]. Clinical studies in adult patients with asthma or atopic dermatitis who were treated with dupilumab concluded that the efficacy of several different vaccines, including tetanus, quadrivalent meningococcal polysaccharide, and live-attenuated yellow fever vaccines, was not affected by concomitant biologic use [31, 32]. The findings from the VECTOR study provide evidence that treatment with tezepelumab does not impact the humoral immune response to influenza vaccination and add to the available evidence supporting the continued use of biologic therapies during administration of activated vaccines [33].

In addition to studies of biologics on vaccination response in patients with asthma, it has been reported that systemic corticosteroid treatment in children with asthma did not impact the immune response to influenza vaccination [25], and that long-term oral or inhaled corticosteroid therapy did not affect the immune response to influenza vaccination in elderly patients with asthma or other chronic pulmonary diseases [34]. However, there is some evidence to suggest that treatment with high-dose inhaled corticosteroids may reduce the immune response to influenza B [35].

Serum concentrations of tezepelumab were quantifiable in all treated patients at week 12 and approached a PK steady state by week 12, consistent with observations in previous studies [14]. Tezepelumab was well tolerated by patients in this study, with no new or unexpected safety findings; this is also consistent with previous studies assessing the safety of tezepelumab [10, 11, 36, 37].

This study was limited by the small patient population, which was a result of challenges with recruitment, namely, truncation of the enrollment period to coincide with the winter influenza vaccination season in the USA, slow site initiation, and unwillingness of some sites to participate owing to the ongoing COVID-19 pandemic and the requirement to delay influenza vaccination to October or November. However, the COVID-19 pandemic was not judged to have impacted the overall conduct of the study, the study data obtained, or the interpretation of the study results.

Conclusions

In this study, there was no observed suppression of the humoral immune response after influenza vaccination in adolescents and young adults with moderate to severe asthma who were treated with tezepelumab compared with placebo. This finding is important because it demonstrates that inactivated vaccines such as the influenza vaccine are immunogenic and can be safely administered to this patient population while receiving treatment with tezepelumab.