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How to choose a reliable influenza vaccine during the flu season? An evidence-based guide for subunit vaccines for all age groups

How to choose a reliable influenza vaccine during the flu season? An evidence-based guide for subunit vaccines for all age groups

  • Categories:Industry news
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  • Time of issue:2026-09-01
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(Summary description)Influenza (commonly referred to as the flu) is an acute respiratory infectious disease caused by the influenza virus. Unlike the common cold, influenza is highly contagious and is characterized primarily by systemic symptoms. Elderly individuals, children under the age of 5, patients with chronic diseases, pregnant women, and individuals with compromised immune systems are all considered high-risk populations for severe influenza [1]. A study based on national influenza surveillance and cause-of-death surveillance data revealed that, on average, there are 88,000 excess deaths related to influenza-associated respiratory diseases annually across China [2]. The total economic burden on outpatient patients with influenza ranges from RMB 801 to RMB 1,320, while the total economic burden on hospitalized influenza patients ranges from RMB 9,832 to RMB 23,833 [1]. In the face of the significant challenge posed by influenza, influenza vaccination is currently recognized worldwide as the most cost-effective and effective means of preventing influenza [1].

How to choose a reliable influenza vaccine during the flu season? An evidence-based guide for subunit vaccines for all age groups

(Summary description)Influenza (commonly referred to as the flu) is an acute respiratory infectious disease caused by the influenza virus. Unlike the common cold, influenza is highly contagious and is characterized primarily by systemic symptoms. Elderly individuals, children under the age of 5, patients with chronic diseases, pregnant women, and individuals with compromised immune systems are all considered high-risk populations for severe influenza [1]. A study based on national influenza surveillance and cause-of-death surveillance data revealed that, on average, there are 88,000 excess deaths related to influenza-associated respiratory diseases annually across China [2]. The total economic burden on outpatient patients with influenza ranges from RMB 801 to RMB 1,320, while the total economic burden on hospitalized influenza patients ranges from RMB 9,832 to RMB 23,833 [1]. In the face of the significant challenge posed by influenza, influenza vaccination is currently recognized worldwide as the most cost-effective and effective means of preventing influenza [1].

  • Categories:Industry news
  • Author:
  • Origin:
  • Time of issue:2026-09-01 10:21
  • Views:
Information

Influenza (commonly referred to as the flu) is an acute respiratory infectious disease caused by the influenza virus. Unlike the common cold, influenza is highly contagious and is characterized primarily by systemic symptoms. Elderly individuals, children under the age of 5, patients with chronic diseases, pregnant women, and individuals with compromised immune systems are all considered high-risk populations for severe influenza [1]. A study based on national influenza surveillance and cause-of-death surveillance data revealed that, on average, there are 88,000 excess deaths related to influenza-associated respiratory diseases annually across China [2]. The total economic burden on outpatient patients with influenza ranges from RMB 801 to RMB 1,320, while the total economic burden on hospitalized influenza patients ranges from RMB 9,832 to RMB 23,833 [1]. In the face of the significant challenge posed by influenza, influenza vaccination is currently recognized worldwide as the most cost-effective and effective means of preventing influenza [1].

However, China's influenza vaccination coverage rate has long remained at an extremely low level. Data indicate that the overall influenza vaccination rate among the Chinese population is less than 4%, representing a significant disparity compared to the approximately 50% vaccination rate observed in the United States [3]. Research findings show that the average annual influenza vaccination rate across the Chinese population stands at only 2%–3%; specifically, the vaccination rate among individuals aged 60 years or older is 3.8%, among people with chronic diseases it is 4.0%, and among children (aged ≤5 years) the average vaccination rate is 26% [4]. This situation is attributable to multiple factors, including insufficient public awareness of influenza and lingering vaccine-related concerns. In reality, with the continuous advancement of vaccine technologies, their efficacy and safety have been thoroughly validated, providing the public with a reliable means of protection.

Influenza vaccination hesitancy: multiple challenges involving cognition, trust, and safety

Vaccine hesitancy is one of the important factors influencing vaccination rates. Studies have shown that the proportion of influenza vaccine hesitancy reaches as high as 55.29% [5]. This vaccine hesitancy is influenced by various factors, including the age, educational background, occupation of the recipient or their guardian, as well as concerns regarding the efficacy and safety of the vaccine [5].

This hesitancy is observed across diverse population groups. Among infants, young children, and preschool-aged children, only 57.2% of respondents are willing to have their children vaccinated against influenza, and merely 39.8% of parents have a correct understanding of the severity of influenza infection [6]. Among pregnant women, 53.6% express hesitation about receiving the influenza vaccine, primarily due to safety concerns and the traditional belief that pharmacological interventions should be avoided during pregnancy [7]. The situation is equally concerning among older adults; even during the peak influenza season, the influenza vaccination rate among residents aged 60 and older stands at only 4.3% [6].

In response to these practical challenges, to enhance vaccination willingness, in addition to strengthening public health education and raising public awareness about influenza and vaccines, it is equally important to provide vaccine products that offer higher safety profiles and broader applicability. Currently, there are three main types of influenza vaccines approved for use in China: split-virus vaccines, subunit vaccines, and live attenuated vaccines [1]. As a third-generation influenza vaccine, the subunit influenza vaccine is derived from conventional split-virus vaccines by isolating only the effective antigens hemagglutinin and neuraminidase; this formulation features higher purity, fewer impurities, fewer adverse reactions, as well as excellent immunogenicity and safety [8].

Coverage of the entire population aged 6 months and older: Evidence on the immunogenicity and safety of the influenza virus subunit vaccine

In 2023, the quadrivalent influenza virus subunit vaccine, independently developed by Ab&B Bio-Tech CO.,LTD.JS (hereinafter referred to as "Ab&B Bio"), was approved for market launch, filling a gap in China's high-end influenza vaccine market; in January 2026, its next-generation trivalent influenza virus subunit vaccine (Huierkangxin 3) was approved, and it received batch release and was officially launched into the market in August [9]. As the first and only subunit influenza vaccine in China suitable for the entire population aged 6 months and older, this vaccine precisely covers the three currently circulating influenza strains: A/H1N1, A/H3N2, and B (Victoria lineage). The relevant research findings have been frequently cited in authoritative domestic clinical practice guidelines; its efficacy and safety have been rigorously validated through rigorous clinical trials and large-scale real-world safety studies involving diverse age groups, demonstrating outstanding performance across all age cohorts [8].

*As of the date of publication*

The "Technical Guidelines for Influenza Vaccination in China (2025–2026)" specify that subunit vaccines may be administered to individuals aged 6 months and older [8]. Based on the latest research evidence, the Guidelines provide clear affirmation of the clinical evidence-based data regarding the immunogenicity and safety of the Ab&B subunit influenza vaccine: In terms of immunogenicity, multiple clinical studies have demonstrated that administration of the subunit influenza vaccine to individuals aged 6 months and older elicits favorable immune responses; among these, infants and young children aged 6–35 months who receive the full-dose (0.5 mL) vaccine exhibit better immunogenicity than those who receive the half-dose (0.25 mL) vaccine. Regarding safety, subunit vaccines, by removing internal viral proteins, possess higher purity of the active antigen component, resulting in superior safety profiles compared to split-virus vaccines; the overall incidence of adverse events following vaccination in individuals aged 18–64 years is lower than that observed with split-virus vaccines and shows a statistically significant difference; furthermore, among children aged 6–35 months, the incidence of systemic adverse reactions following administration of the 0.5 mL quadrivalent influenza subunit vaccine does not differ statistically from that observed with the 0.25 mL dose formulation, while the incidence of local adverse reactions is lower [8].

Infants and young children aged 6–35 months: The full-dose subunit vaccine elicits a superior immune response with fewer local adverse reactions.

Infants and young children represent a high-risk population for influenza and are a key target group for vaccination. To evaluate the safety and immunogenicity of an influenza virus subunit vaccine in infants and young children aged 6–35 months, researchers conducted a multicenter, randomized, blinded, positively controlled phase III clinical trial. A total of 2,772 healthy infants and young children aged 6–35 months were enrolled in this study. By comparing the subunit vaccine group (0.5 mL) with the split-virus vaccine group (0.25 mL), the results demonstrated [10]:

In terms of immunogenicity, compared to the split-virus vaccine, the subunit vaccine group demonstrated a significant increase in the geometric mean titers (GMT) against all three influenza virus strains—H1N1, H3N2, and B/Yamagata (B/Y) (P<0.05); a significant increase in the seroconversion rate (SCR) against all four influenza virus types—H1N1, H3N2, B/Y, and B/Victoria (B/V) (P<0.01); and a significant increase in the antibody protection rate (as measured by hemagglutination inhibition [HI] antibody titers ≥1:40) against all three influenza virus types—H1N1, H3N2, and B/V (P<0.01). These findings indicate that the subunit vaccine exhibits favorable immunogenicity and is not inferior to the split-virus vaccine [10].

Regarding safety, the overall incidence rate of adverse reactions (from the first dose to 30 days after the second dose) was 29.64% for both the subunit vaccine and the whole-cell vaccine; the majority of adverse reactions occurred within the first 7 days after vaccination (including within 30 minutes), and there was no statistically significant difference between the two groups. Additionally, the local adverse reaction incidence rate in the subunit vaccine group was lower than that in the whole-cell vaccine group (P <0.05), amounting to only 54% of the incidence rate observed in the whole-cell vaccine group [10].

As demonstrated, the full-dose subunit influenza vaccine developed by Ab&B Bio exhibits favorable immunogenicity and safety profiles in children aged 6–35 months, providing optimal protection for this population. Notably, Huierkangxin-3 is currently the only trivalent subunit influenza vaccine approved in China for use in infants and young children aged 6–35 months [9], which breaks away from the traditional practice of reducing the pediatric dose by half and instead recommends a uniform full-dose administration of 0.5 mL across all age groups. Parents no longer need to worry about choosing the appropriate vaccine formulation.

Individuals aged ≥3 years: enhanced immune response and reduced risk of adverse vaccination reactions

For individuals aged 3 years and older, a randomized, multicenter, double-blind, placebo-controlled Phase III clinical trial involving 3,000 participants provided robust evidence. Participants were stratified into four age groups—3–8 years, 9–17 years, 18–64 years, and ≥65 years—and within each group, they were further randomly assigned in a 1:1 ratio to receive either a subunit vaccine (0.5 mL) or a whole-cell vaccine (0.5 mL). The study results [11] showed:

Regarding immunogenicity, in individuals aged 3 years and older, the GMT for the quadrivalent subunit influenza vaccine against the four vaccine strains (H1N1, H3N2, B/V, and B/Y) was higher than that observed in the control group; with respect to seroconversion (SCR), the seroconversion rates for all four vaccine strains were higher than those in the control group; in particular, the SCR for the H1N1, B/V, and B/Y strains was significantly higher than that in the control group, with a statistically significant difference. These findings demonstrate favorable immunogenicity, enabling the vaccine to provide recipients with more effective protection [11].

In terms of safety, the quadrivalent subunit influenza vaccine can further reduce the incidence of adverse reactions following immunization and demonstrates superior safety profile [11]:

  • Among adults aged 18–64 years who received vaccination within 0–30 days after administration, the overall incidence of adverse reactions was significantly lower than that in the control group, amounting to only 58% of the control group's incidence rate;
  • Among children aged 3–8 years who received vaccination, the incidence of febrile reactions within 0–30 days post-vaccination was significantly lower than that in the control group—only 46% of the control group's incidence rate.

Furthermore, a Phase IV clinical trial utilizing over 42,000 real-world data points (n=42,881) based on an active surveillance approach further confirmed the favorable safety profile of this vaccine in individuals aged ≥3 years; the incidence rate of adverse reactions (ADR) following vaccination was 6.83 per 1,000, and no vaccine-related serious adverse events were reported [12].

brief summary

Influenza vaccination represents the most effective and cost-efficient public health measure for preventing influenza. Currently, the influenza vaccination coverage rate in China remains at an extremely low level—less than 4% across the general population, merely 3.8% among individuals aged 60 years or older, 4.0% among people with chronic diseases, and only 26% among children aged ≤5 years; concerns regarding vaccine safety are one of the primary influencing factors. The third-generation subunit influenza vaccine employs a precision purification process to remove impurity proteins from the viral structure while retaining high-purity hemagglutinin and neuraminidase surface antigens, thereby reducing the risk of adverse reactions without compromising immunogenicity.

As China's first and only subunit influenza vaccine designed to cover the entire population aged 6 months and older, the launch of Huierkangxin III addresses the gap in the country's supply of high-quality influenza vaccines across all age groups. Multiple clinical studies have demonstrated its efficacy and safety profile in eliciting immune responses among individuals of all age ranges; furthermore, large-scale active surveillance data collected post-approval further support its favorable safety profile. Selecting an influenza vaccine with a proven safety record helps bolster public confidence in vaccination and represents an important measure in advancing influenza prevention and control efforts and safeguarding public health.

References

  1. National Health Commission of the People's Republic of China. Clinical Diagnosis and Treatment Guidelines for Influenza (2025 Edition) [EB/OL]. (2025-01-20).
  2. Gong Hui, Shen Xin, Yan Han, et al. Estimation of the disease burden of seasonal influenza in China, 2006–2019 [J]. National Medical Journal of China, 2021,101(8):560–567.
  3. Jiang Youshan, Cao Yinglin, Feng Luzhao, et al. Multi-dimensional approaches to advancing vaccination policies and promoting the adoption of influenza vaccines in China [R]. Kunshan Duke University Vaccine Delivery Research Innovation Laboratory, September 2023.
  4. Chen Chen, Liu Guo'en, Zeng Guang. Current status, issues, challenges and response strategies regarding the disease burden of influenza in China [J]. Chinese Journal of Public Health, 2022,38(11):1494–1498.
  5. Jia Yachao, Hou Qian, Yang Yuzhen, et al. Analysis of influenza vaccine hesitancy among individual social media users in China and its underlying causes (March 2021 – March 2024) [J]. China Vaccines and Immunization, 2025,31(1):14–19.
  6. Zhao Shuangyu, Dong Shuheng, Li Xinchen, et al. Current status and influencing factors of vaccine hesitancy among priority populations for influenza vaccination in China [J]. Chinese Journal of Preventive Medicine, 2021,22(10):798–803.
  7. Tao Y, Sun N, Wang Y, Tao Y, Sun N, Wang Y, et al. Influencing factors of pregnant women's willingness to receive influenza vaccination in China[J]. Vaccines, 2025, 13(4): 376.
  8. National Immunization Program Technical Working Group – Influenza Vaccine Working Group. Technical Guidelines for Influenza Vaccination in China (2025–2026) [J]. Chinese Journal of Epidemiology, 2025,46(12):2097–2107.
  9. National Medical Products Administration. Trivalent Influenza Virus Subunit Vaccine (Huirkangxin 3) – Drug Registration Certificate [Z]. 2026.
  10. Huang L L, Li G F, Zhang Y H, Huang L L, Li G F, Zhang Y H, et al. The safety and immunogenicity of a quadrivalent influenza subunit vaccine in healthy children aged 6-35 months: a randomized, blinded and positive-controlled phase III clinical trial[J]. Vaccines, 2025, 13(5): 467.
  11. Zhang Y H, Wang Y X, Jia C Y, Zhang Y H, Wang Y X, Jia C Y, et al. Immunogenicity and safety of an egg culture-based quadrivalent inactivated non-adjuvanted subunit influenza vaccine in subjects ≥3 years: a randomized, multicenter, double-blind, active-controlled phase III, non-inferiority trial[J]. Vaccine, 2022.
  12. Wei M W, Pan Y, Wang K N, Wei M W, Pan Y, Wang K N, et al. Post-marketing active surveillance of adverse events following quadrivalent subunit influenza vaccine in healthy participants aged ≥ 3 years in China[J]. Infectious Diseases and Therapy, 2026, 15: 1763-1778.

 

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