Pandemic preparedness through vaccine development for avian influenza viruses

Figures & data

Figure 1. Cumulative global cases and deaths of human infections with H5N1, H7N9, and H9N2 avian influenza viruses reported to the World Health Organization (WHO). Cases and deaths are cumulative from the first reported case of each virus subtype in humans until February 22, 2024. Numbers on top of the bars indicate how many cases and deaths have been reported to the WHO. Note: as of February 22, 2024, two deaths have been reported from H9N2 infections according to the WHO. Due to the limited scale of the figure, these deaths are not visually represented, but the number is included in the graph.

Figure 2. (a) H5N1, H7N9, and H9N2 influenza subtypes from avian sources can infect humans and cause disease. Sustained human-to-human transmission of these subtypes has not been observed but is required to the emergence of pandemic viruses which could further spread within the human population. (b) vaccine development and vaccination of humans can prevent infections and the generation of pandemic viruses, improving pandemic preparedness and management against avian influenza viruses. This figure was created with BioRender.com.

Table 1. Available candidate vaccine viruses for pandemic preparedness against the H5N1, H7N9, and H9N2 subtypes for the northern hemisphere influenza seasons 2024–2025.

Candidate vaccine virus	Antigenic prototype	Subtype	Clade	Institution responsible
SJRG-161052	A/Vietnam/1203/2004	H5N1	1	SJCRH, CDC
IDCDC-RG34B	A/Cambodia/X0810301/2013	H5N1	1.1.1	CDC
SJRG-166614	A/duck/Hunan/795/2002	H5N1	2.1	SJCRH
IDCDC-RG2	A/Indonesia/5/2005	H5N1	2.1.3.2	CDC
IBCDC-RG7	A/chicken/India/NIV33487/2006	H5N1	2.2	CDC
IDCDC-RG11	A/Egypt/2321-NAMRU3/2007	H5N1	2.2.1	CDC
IDCDC-RG13	A/Egypt/3300-NAMRU3/2008	H5N1	2.2.1.1	CDC
IDCDC-RG30	A/Hubei/1/2010	H5N1	2.3.2.1a	CDC
SJ0009	A/chicken/Guiyang/1153/2016	H5N1	2.3.2.1d	SJCRH
IDCDC-RG6	A/Anhui/1/2005	H5N1	2.3.4	CDC
IDCDC-RG35	A/Guizhou/1/2013	H5N1	2.3.4.2	CDC
SJRG-165396	A/goose/Guiyang/337/2006	H5N1	4	SJCRH
IDCDC-RG25A	A/chicken/Vietnam/NCVD-016/2008	H5N1	7.1	CDC
IDCDC-RG63A	A/duck/Bangladesh/17D1012/2018	H5N1	2.3.2.1a	CDC
IDCDC-RG78A	A/American wigeon/South Carolina/22000345-001/2021-like	H5N1	2.3.4.4b	CDC
NIID-002	A/Ezo red fox/Hokkaido/1/2022-like	H5N1	2.3.4.4b	NIID, Japan
IDCDC-RG56N	A/Guangdong/17SF003/2016	H7N9	n/a*	CDC
IDCDC-RG56B	A/Hong Kong/125/2017	H7N9	n/a*	CDC
IDCDC-RG32A	A/Shanghai/2/2013	H7N9	n/a*	CDC
IDCDC-RG33A	A/Anhui/1/2013	H7N9	n/a*	CDC
IDCDC-RG64A	A/Gansu/23277/2019-like	H7N9	n/a*	CDC
IBCDC-2	A/chicken/Hong Kong/G9/97	H9N2	Y280/G9	CDC
IBCDC-RG26	A/Hong Kong/33982/2009	H9N2	G1	CDC
IDCDC-RG31	A/Bangladesh/994/2011	H9N2	G1	CDC
SJ008	A/Hong Kong/308/2014	H9N2	Y280/G9	SJCRH
IDCDC-RG61A	A/Anhui-Lujiang/39/2018	H9N2	Y280/G9	CDC
IDCDC-RG66A	A/Oman/2747/2019	H9N2	G1	CDC

Only one candidate vaccine virus per clade is shown for H5N1 viruses, except clade 2.3.4.4b. * n/a: not available. CDC: Centers for Disease Control and Prevention; SJCRH: St. Jude Children’s Research Hospital; NIID: National Institute of Infectious Diseases, Japan.

Figure 3. Summary of animal data for H5N1, H7N9, and H9N2 vaccines tested in mice, ferrets, and non-human primates. The figure categorizes vaccines by platform (inactivated, live attenuated, and alternative) and uses color-coded boxes for each category. It is important to note that only data from vaccines discussed in this review for each animal model are included. While other platforms exist, they are not discussed in detail within this manuscript. This figure was created with BioRender.com.

Table 2. Summary of clinical trials for H5N1, H7N9, and H9N2 avian influenza vaccines.

Subtype	Vaccine Description	Doses (Ag)	Phase	Outcomes	Trial ID	Reference
H5N1	Inactivated whole virus adjuvanted (aluminum hydroxide)	1.25, 2.5, 5, 10, 15, and 30 μg	1, 2/3	Safe and well-tolerated; two doses generated high levels of neutralizing antibodies	NCT00356798 NCT02612909	94 96
H7N9	Inactivated whole virus adjuvanted (aluminum hydroxide)	7.5, 15, and 30 μg	1/2	Safe and immunogenic; two doses induced an HI titer above 40 in 98.2% of participants	NCT03369808	97
H9N2	Inactivated whole virus nonadjuvanted	3.75, 7.5, 15, 30, and 45 µg	1/2	Safe and well-tolerated; 52.8% to 88.9% of participants developed antibody levels predictive of protection	NCT01320696	98
H5N1*	Split virus	90 µg is approved. Tested: 7.5, 15, and 30 µg	1/2, 3	Safe and well-tolerated in all age groups; elicited neutralizing and HI titers; licensed in the US	NCT00457509 NCT00415129	102 103 105
H5N1*	Split virus adjuvanted (AS03)	3.75 µg is approved.	1/2, 3, 4	Safe and well-tolerated; high neutralizing seroconversion rates; elicited robust antibody responses against homologous and heterologous strains; licensed in the US	NCT00510874 NCT00616928 NCT01730378 NCT01788228 NCT01310413	107 108 109
H5N1*	Subunit vaccine adjuvanted (MF59)	7.5 µg is approved. Tested: 3.75 µg	1/2, 3, 4	Safe and well-tolerated; high seroconversion rates, elicited neutralizing antibodies and HI titers; licensed in the US	NCT01776554 NCT02839330 NCT00812019 NCT01776541	111 112 113 114
H7N9	Subunit vaccine adjuvanted	3.75, 7.5, and 15 µg	1	Safe; adjuvant was necessary to increase HI titers	NCT01928472 NCT03682120	n/a
H9N2	Subunit vaccine adjuvanted	3.75, 7.5, 15, and 30 µg	1	Safe and well-tolerated; prime induced protective levels of antibodies	NCT00133471	99
H7N9	Split virus adjuvanted (oil-in-water IB160 or SE)	3.75, 7.5, and 15 µg	1	Safe and well-tolerated; adjuvanted formulations elicited a significantly greater increase in antibody titers	NCT03330899	115
H7N9	Split virus adjuvanted (AS03)	2.78, 3.75, and 5.08 µg	1, 2	Enhanced immune responses and good tolerability were observed compared to unadjuvanted or alum-adjuvanted formulations	NCT01999842 NCT03318315	116 117
H9N2	Split virus adjuvanted (AS03)	1.9, 3.75, and 15 µg	1/2	Safe and well-tolerated; the adjuvanted vaccine generated a seroconversion rate of ≥ 98.1%, both higher than the unadjuvanted vaccine	NCT01659086	118
H5N1	Live attenuated cold-adapted	10^6.7 and 10^7.5 TCID50	1/2	Safe, restricted in replication; IgA and IgG were detected by ELISA in the serum	NCT00347672 NCT00488046	121
H7N9	Live attenuated cold-adapted	10^7.5 TCID50	1	Safe and well-tolerated; increase in neutralizing antibodies, serum IgG and IgA, mucosal IgA, CD4+, and CD8+ virus-specific T cells	NCT02480101 NCT03739229 NCT01995695 NCT02274545	125 126 127
H9N2	Live attenuated cold-adapted	10^Citation7 and 2 × 10^Citation7 TCID50	1	Well-tolerated, exhibited an attenuated phenotype; Following two doses, 92% of participants showed greater than a 4-fold increase in HI titers, with 79% having a similar increase in neutralizing antibody titers	NCT00110279	128
H5N1	Virus-like particle	5, 10, and 20 µg	1, 2	Well-tolerated; nearly 96% of individuals in the higher dose groups developed neutralizing antibody responses	NCT00984945 NCT01991561	140 147
H7N9	Virus-like particle	5, 15, and 30 µg	1	Well-tolerated; robust HI and neutralizing antibody responses	NCT01897701	141
H7N9	mRNA	10, 25, and 50 µg	1	Safe and well-tolerated; 100% of participants seroconverted against the H7N9 strain.	NCT03076385 NCT03345043	146
H5N1	Recombinant, protein-based adjuvanted (SE) Recombinant, protein-based adjuvanted (GLA/SE)	3.8, 7.5 and 15 µg 3.8, 7.5, 15, 45, 135 µg	1/2 1/2	Well-tolerated; 70% of participants receiving adjuvant seroconverted. Well-tolerated and immunogenic; GLA/SE improved serum antibody responses	NCT01612000 NCT01147068	148 149
H7N9	Recombinant, protein-based adjuvanted (SE or MF59)	7.5, 15, and 30 µg	1/2	Strong induction of anti-H7 antibodies; lacking neutralizing antibodies	NCT02464163 NCT05608005	150

This table includes clinical trials, across all phases, with published results or results posted online. Trial IDs can be found at clinicaltrials.gov. * Vaccines that have been licensed for use in the United States by the United States Food and Drug Administration (FDA). Ag: antigen. AS03: adjuvant system 03; IB160: oil-in-water adjuvant emulsion; SE: stable emulsion; GLA/SE: glucopyranosyl lipid A/stable emulsion. n/a: a publication related to the clinical trial was not available.

Lin J, Zhang J, Dong X, Fang H, Chen J, Su N, Gao Q, Zhang Z, Liu Y, Wang Z. et al. Safety and immunogenicity of an inactivated adjuvanted whole-virion influenza a (H5N1) vaccine: a phase I randomised controlled trial. Lancet. 2006;368(9540):991–7. doi:10.1016/S0140-6736(06)69294-5.

 PubMed Web of Science ®Google Scholar

Duong TN, Thiem VD, Anh DD, Cuong NP, Thang TC, Huong VM, Chien VC, Phuong NTL, Montomoli E, Holt R. et al. A phase 2/3 double blinded, randomized, placebo-controlled study in healthy adult participants in Vietnam to examine the safety and immunogenicity of an inactivated whole virion, alum adjuvanted, A(H5N1) influenza vaccine (IVACFLU-A/H5N1). Vaccine. 2020;38(6):1541–50. doi:10.1016/j.vaccine.2019.11.059.

 PubMed Web of Science ®Google Scholar

Wang S, Xie Z, Huang L, Zhou X, Luo J, Yang Y, Li C, Duan P, Xu W, Chen D. et al. Safety and immunogenicity of an alum-adjuvanted whole-virion H7N9 influenza vaccine: a randomized, blinded, clinical trial. Clin Microbiol Infect. 2020;27(5):775–81. doi:10.1016/j.cmi.2020.07.033.

 Web of Science ®Google Scholar

Aichinger G, Grohmann-Izay B, van der Velden MV, Fritsch S, Koska M, Portsmouth D, Hart MK, El-Amin W, Kistner O, Barrett PN. et al. Phase I/II randomized double-blind study of the safety and immunogenicity of a nonadjuvanted vero cell culture-derived whole-virus H9N2 influenza vaccine in healthy adults. Clin Vaccine Immunol. 2015;22(1):46–55. doi:10.1128/CVI.00275-14.

 PubMedGoogle Scholar

Bresson JL, Perronne C, Launay O, Gerdil C, Saville M, Wood J, Höschler K, Zambon MC. Safety and immunogenicity of an inactivated split-virion influenza A/Vietnam/1194/2004 (H5N1) vaccine: phase I randomised trial. Lancet. 2006;367(9523):1657–64. doi:10.1016/S0140-6736(06)68656-X.

 PubMed Web of Science ®Google Scholar

Levie K, Leroux-Roels I, Hoppenbrouwers K, Kervyn AD, Vandermeulen C, Forgus S, Leroux‐Roels G, Pichon S, Kusters I. An adjuvanted, low-dose, pandemic influenza a (H5N1) vaccine candidate is safe, immunogenic, and induces cross-reactive immune responses in healthy adults. J Infect Dis. 2008;198(5):642–9. doi:10.1086/590913.

 PubMed Web of Science ®Google Scholar

Lazarus R, Kelly S, Snape MD, Vandermeulen C, Voysey M, Hoppenbrouwers K, Hens A, Van Damme P, Pepin S, Leroux-Roels I. et al. Antibody persistence and booster responses to split-virion H5N1 avian influenza vaccine in young and elderly adults. PLOS ONE. 2016;11(11):e0165384. doi:10.1371/journal.pone.0165384.

 PubMed Web of Science ®Google Scholar

Langley JM, Frenette L, Ferguson L, Riff D, Sheldon E, Risi G, Johnson C, Li P, Kenney R, Innis B. et al. Safety and cross-reactive immunogenicity of candidate AS03-adjuvanted prepandemic H5N1 influenza vaccines: a randomized controlled phase 1/2 trial in adults. J Infect Dis. 2010;201(11):1644–53. doi:10.1086/652701.

 PubMed Web of Science ®Google Scholar

Langley JM, Risi G, Caldwell M, Gilderman L, Berwald B, Fogarty C, Poling T, Riff D, Baron M, Frenette L. et al. Dose-sparing H5N1 A/Indonesia/05/2005 pre-pandemic influenza vaccine in adults and elderly adults: a phase III, placebo-controlled, randomized study. J Infect Dis. 2011;203(12):1729–38. doi:10.1093/infdis/jir172.

 PubMed Web of Science ®Google Scholar

Izurieta P, Kim WJ, Wie SH, Lee J, Lee JS, Drame M, Vaughn DW, Schuind A. Immunogenicity and safety of an AS03-adjuvanted H5N1 pandemic influenza vaccine in Korean adults: a phase IV, randomized, open-label, controlled study. Vaccine. 2015;33(24):2800–7. doi:10.1016/j.vaccine.2015.04.027.

 PubMed Web of Science ®Google Scholar

Chanthavanich P, Anderson E, Kerdpanich P, Bulitta M, Kanesa-Thasan N, Hohenboken M. Safety, tolerability and immunogenicity of an MF59-adjuvanted, Cell Culture-derived, A/H5N1, subunit influenza virus vaccine: results from a Dose-finding Clinical Trial in healthy pediatric subjects. Pediatr Infect Dis J. 2019;38:757–64. doi:10.1097/INF.0000000000002345.

 PubMed Web of Science ®Google Scholar

Peterson J, Van Twuijver E, Versage E, Hohenboken M. Phase 3 randomized, multicenter, placebo-controlled study to evaluate safety, immunogenicity, and lot-to-lot consistency of an adjuvanted cell culture-derived, H5N1 subunit influenza virus vaccine in healthy adult subjects. Vaccines. 2022;10(4):497. doi:10.3390/vaccines10040497.

 Web of Science ®Google Scholar

Frey SS, Versage E, Van Twuijver E, Hohenboken M. Antibody responses against heterologous H5N1 strains for an MF59-adjuvanted cell culture–derived H5N1 (aH5n1c) influenza vaccine in adults and older adults. Hum Vaccin Immunother. 2023;19(1):2193119. doi:10.1080/21645515.2023.2193119.

 PubMed Web of Science ®Google Scholar

Frey SE, Shakib S, Chanthavanich P, Richmond P, Smith T, Tantawichien T, Kittel C, Jaehnig P, Mojares Z, Verma B. et al. Safety and Immunogenicity of MF59-Adjuvanted Cell Culture–derived A/H5N1 subunit influenza virus vaccine: Dose-Finding Clinical Trials in adults and the elderly. Open Forum Infect Dis. 2019;6(4):ofz107. doi:10.1093/ofid/ofz107.

 PubMed Web of Science ®Google Scholar

Stephenson I, Nicholson KG, Gluck R, Mischler R, Newman RW, Palache AM, Verlander NQ, Warburton F, Wood JM, Zambon MC. et al. Safety and antigenicity of whole virus and subunit influenza A/Hong Kong/1073/99 (H9N2) vaccine in healthy adults: phase I randomised trial. Lancet. 2003;362(9400):1959–66. doi:10.1016/S0140-6736(03)15014-3.

 PubMed Web of Science ®Google Scholar

Vanni T, Thome BC, Sparrow E, Friede M, Fox CB, Beckmann AM, Huynh C, Mondini G, Silveira DH, Viscondi JYK. et al. Dose-sparing effect of two adjuvant formulations with a pandemic influenza A/H7N9 vaccine: a randomized, double-blind, placebo-controlled, phase 1 clinical trial. PLOS ONE. 2022;17(10):e0274943. doi:10.1371/journal.pone.0274943.

 PubMed Web of Science ®Google Scholar

Ortiz JR, Spearman PW, Goepfert PA, Cross K, Buddy Creech C, Chen WH, Parker S, Overton ET, Dickey M, Logan HL. et al. Safety and immunogenicity of monovalent H7N9 influenza vaccine with AS03 adjuvant given sequentially or simultaneously with a seasonal influenza vaccine: a randomized clinical trial. Vaccine. 2022;40(23):3253–62. doi:10.1016/j.vaccine.2022.03.055.

 PubMed Web of Science ®Google Scholar

Madan A, Segall N, Ferguson M, Frenette L, Kroll R, Friel D, Soni J, Li P, Innis BL, Schuind A. Immunogenicity and safety of an AS03-adjuvanted H7N9 pandemic influenza vaccine in a randomized trial in healthy adults. J Infect Dis. 2016;214(11):1717–27. doi:10.1093/infdis/jiw414.

 PubMed Web of Science ®Google Scholar

Madan A, Collins H, Sheldon E, Frenette L, Chu L, Friel D, Drame M, Vaughn DW, Innis BL, Schuind A. et al. Evaluation of a primary course of H9N2 vaccine with or without AS03 adjuvant in adults: a phase I/II randomized trial. Vaccine. 2017;35(35):4621–8. doi:10.1016/j.vaccine.2017.07.013.

 PubMed Web of Science ®Google Scholar

Rudenko L, Desheva J, Korovkin S, Mironov A, Rekstin A, Grigorieva E, Donina S, Gambaryan A, Katlinsky A. Safety and immunogenicity of live attenuated influenza reassortant H5 vaccine (phase I–II clinical trials). Influenza Other Respir Viruses. 2008;2(6):203–9. doi:10.1111/j.1750-2659.2008.00064.x.

 PubMed Web of Science ®Google Scholar

Rudenko L, Isakova-Sivak I, Naykhin A, Kiseleva I, Stukova M, Erofeeva M, Korenkov D, Matyushenko V, Sparrow E, Kieny M-P. et al. H7N9 live attenuated influenza vaccine in healthy adults: a randomised, double-blind, placebo-controlled, phase 1 trial. Lancet Infect Dis. 2016;16(3):303–10. doi:10.1016/S1473-3099(15)00378-3.

 PubMed Web of Science ®Google Scholar

Kiseleva I, Isakova-Sivak I, Stukova M, Erofeeva M, Donina S, Larionova N, Krutikova E, Bazhenova E, Stepanova E, Vasilyev K. et al. A phase 1 randomized placebo-controlled study to assess the safety, immunogenicity and genetic stability of a new potential pandemic H7N9 live attenuated influenza vaccine in healthy adults. Vaccines. 2020;8(2):296. doi:10.3390/vaccines8020296.

 Web of Science ®Google Scholar

Sobhanie M, Matsuoka Y, Jegaskanda S, Fitzgerald T, Mallory R, Chen Z, Luke C, Treanor J, Subbarao K. Evaluation of the safety and immunogenicity of a Candidate pandemic live attenuated influenza vaccine (pLAIV) against influenza A(H7N9). J Infect Dis. 2016;213(6):922–9. doi:10.1093/infdis/jiv526.

 PubMed Web of Science ®Google Scholar

Kosik I, Yewdell JW. Influenza hemagglutinin and neuraminidase: Yin–Yang Proteins coevolving to thwart immunity. Viruses. 2019;11(4):346. doi:10.3390/v11040346.

 PubMed Web of Science ®Google Scholar

Karron RA, Callahan K, Luke C, Thumar B, McAuliffe J, Schappell E, Joseph T, Coelingh K, Jin H, Kemble G, et al. A live attenuated H9N2 influenza vaccine is well tolerated and immunogenic in healthy adults. J Infect Dis. 2009;199(5):711–6. doi:10.1086/596558.

 PubMed Web of Science ®Google Scholar

Landry N, Ward BJ, Trepanier S, Montomoli E, Dargis M, Lapini G, Vézina L-P. Preclinical and clinical development of plant-made virus-like particle vaccine against avian H5N1 influenza. PloS One. 2010;5(12):e15559. doi:10.1371/journal.pone.0015559.

 PubMed Web of Science ®Google Scholar

Pillet S, Aubin E, Trepanier S, Poulin JF, Yassine-Diab B, Ter Meulen J, Ward BJ, Landry N. Humoral and cell-mediated immune responses to H5N1 plant-made virus-like particle vaccine are differentially impacted by alum and GLA-SE adjuvants in a phase 2 clinical trial. NPJ Vaccines. 2018;3(1):3. doi:10.1038/s41541-017-0043-3.

 PubMedGoogle Scholar

Chung KY, Coyle EM, Jani D, King LR, Bhardwaj R, Fries L, Smith G, Glenn G, Golding H, Khurana S. et al. ISCOMATRIX™ adjuvant promotes epitope spreading and antibody affinity maturation of influenza a H7N9 virus like particle vaccine that correlate with virus neutralization in humans. Vaccine. 2015;33(32):3953–62. doi:10.1016/j.vaccine.2015.06.047.

 PubMed Web of Science ®Google Scholar

Feldman RA, Fuhr R, Smolenov I, Mick Ribeiro A, Panther L, Watson M, Senn JJ, Smith M, Almarsson Ӧ, Pujar HS. et al. mRNA vaccines against H10N8 and H7N9 influenza viruses of pandemic potential are immunogenic and well tolerated in healthy adults in phase 1 randomized clinical trials. Vaccine. 2019;37(25):3326–34. doi:10.1016/j.vaccine.2019.04.074.

 PubMed Web of Science ®Google Scholar

Treanor JJ, Chu L, Essink B, Muse D, El Sahly HM, Izikson R, Goldenthal KL, Patriarca P, Dunkle LM. Stable emulsion (SE) alone is an effective adjuvant for a recombinant, baculovirus-expressed H5 influenza vaccine in healthy adults: a phase 2 trial. Vaccine. 2017;35(6):923–8. doi:10.1016/j.vaccine.2016.12.053.

 PubMed Web of Science ®Google Scholar

Treanor JJ, Essink B, Hull S, Reed S, Izikson R, Patriarca P, Goldenthal KL, Kohberger R, Dunkle LM. Evaluation of safety and immunogenicity of recombinant influenza hemagglutinin (H5/Indonesia/05/2005) formulated with and without a stable oil-in-water emulsion containing glucopyranosyl-lipid a (SE+GLA) adjuvant. Vaccine. 2013;31(48):5760–5. doi:10.1016/j.vaccine.2013.08.064.

 PubMed Web of Science ®Google Scholar

Stadlbauer D, Rajabhathor A, Amanat F, Kaplan D, Masud A, Treanor JJ, Izikson R, Cox MM, Nachbagauer R, Krammer F. et al. Vaccination with a recombinant H7 hemagglutinin-based influenza virus vaccine induces broadly reactive antibodies in humans. mSphere. 2017;2(6). doi:10.1128/mSphere.00502-17.

 PubMed Web of Science ®Google Scholar