Skip Navigation

Immunogenicity, Safety, and Cross-Reactivity of an Inactivated, Adjuvanted, Prototype Pandemic Influenza (H5N1) Vaccine: A Phase II, Double-Blind, Randomized Trial

  1. Jiang Wu1,a,
  2. Han-Hua Fang2,a,
  3. Jiang-Ting Chen3,
  4. Ji-Chen Zhou4,
  5. Zi-Jian Feng5,
  6. Chang-Gui Li2,
  7. Yuan-Zheng Qiu3,
  8. Yan Liu3,
  9. Min Lu1,
  10. Li-Ying Liu4,
  11. Shan-Shan Dong3,
  12. Qiang Gao3,
  13. Xiao-Mei Zhang3,
  14. Nan Wang3,
  15. Wei-Dong Yin3, and
  16. Xiao-Ping Dong6
  1. 1Beijing Centers for Diseases Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China
  2. 2National Institute for the Control of Pharmaceuticals and Biological Products, Chinese Center for Disease Control and Prevention, Beijing, China
  3. 3Sinovac Biotech, Chinese Center for Disease Control and Prevention, Beijing, China
  4. 4Huairou Center for Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China
  5. 5Chinese Center for Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China
  6. 6State Key Laboratory for Infectious Disease Prevention and Control, National Institute for Viral Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China
  1. Reprints or correspondence: Dr. Xiao-Ping Dong, Ying-Xin Rd. 100, Beijing (100052), People' Republic of China (dongxp238{at}sina.com); or Dr. Wei-Dong Yin, No.39 Shangdi Western Road, Haidian District, Beijing (100085), People's Republic of China (yinweidong{at}sinovac.com).
 
Next Section

Abstract

Background. Avian influenza A virus H5N1 has the potential to cause a pandemic. Adjuvants and whole-virion vaccines are regarded as antigen sparing for pandemic vaccines.

Methods. A double-blind, randomized trial was performed from 28 August to 22 December 2007 in 402 adults; 301 adults were randomly assigned to receive 2 doses of an inactivated, aluminum-adjuvanted, whole-virion H5N1 vaccine containing 5, 10, or 15 μg of hemagglutinin per dose 28 days apart, and 101 of them received 2 doses of 10 μg of vaccine 14 days apart. The vaccine was manufactured from the recombinant A/Vietman/1194/2004 (NIBRG14) strain. Blood samples were collected for hemagglutination inhibition and microneutralization assays.

Results. All formulations were well tolerated, with no serious adverse events. Most local and systemic reactions were mild or moderate. Immune responses were induced after 1 dose in all vaccination groups. The highest immune response was seen after 2 doses of 15 μg of vaccine, with 90% and 100% seroconversion rates and 90% and 100% of participants having a titer of ⩾1:40 for hemagglutination inhibition and microneutralization assays, respectively. Both the 10- and 15-μg doses met or exceeded European Union licensure criteria. Generally, higher immune responses were elicited in participants vaccinated 28 days apart than those vaccinated 14 days apart. Cross-reaction assays showed that after 2 doses of 10 μg of vaccine, 98% and 87% of participants had a microneutralization titer of ⩾1:40 against heterologous Indonesia and Anhui strains, respectively.

Conclusions. The inactivated, aluminum-adjuvanted, whole-virion H5N1 vaccine not only showed good immunogenicity and safety but also elicited significant cross-reactivity against heterologous H5N1 strains in clade 2.

Trial registration. ClinicalTrials.gov identifier: NCT00535665.

Human influenza pandemic had caused tens of millions of deaths in the last century. The threat of a potential influenza pandemic arose again since the first human infection with avian influenza virus H5N1 was reported in Hong Kong in 1997 [1]. The virus is now widespread among poultry and migratory birds [2]. As of 19 June 2008, there were 385 human cases of H5N1 infection, 243 of which were fatal [3]. Although evidence of person-to-person transmission is rare at present [4], the virus has the potential to cause the next influenza pandemic if it evolves into a strain capable of transmission among persons [5].

Influenza vaccines manufactured from seasonal vaccine strains might not provide protection against H5N1, to which human beings are immunologically naive [6]. Therefore, the development of effective vaccines against H5N1 is considerably urgent. Some influenza pandemic vaccine candidates are being developed and assessed clinically [7–14]. Previous trials assessing H5N3, H9N2, and H2N2 vaccines suggest that 2-dose vaccination and an adjuvant are needed to elicit seroprotective response in naive populations and that whole-virion vaccines would elicit better response than subunit or split-virion vaccines did [7, 8, 14]. A recent study suggested that oil-in-water emulsion vaccines allowed significant dose sparing [13].

In previous a phase I trial, an inactivated, aluminum-adjuvanted, whole-virion H5N1 vaccine manufactured by Sinovac Biotech showed good safety and immunogenicity in adults [12]. This dose-finding phase I trial indicated the necessity of further assessment in a dose confirmatory study to provide in-depth understanding of the vaccine.

In this phase II trial, which included a larger population, we report the effects of dosage and regimen on the immunogenicity and safety of the whole-virion H5N1 vaccine. In addition, we investigate the cross-reactivity of the vaccine.

Previous SectionNext Section

Methods

Participants. From 28 August to 22 December 2007, 402 participants were enrolled from a group of clinically healthy volunteers aged 18–60 years. The main exclusion criteria were current febrile illness; any acute diseases; allergic history to vaccines and eggs; history of hematologic, hepatic, renal, cardiac, or respiratory disease; immunodeficiency; treatment with cytotoxic or immunosuppressive drugs within the past 6 months; receipt of blood, blood-derived products, or any other vaccines within the past 3 months; currently attending or planing to attend any other trials; and being unable to comply with the visit schedule. Woman participants with positive urine pregnancy test results or who planned to be pregnant were excluded.

The trial was approved by the Chinese State Food and Drug Administration and was registered with ClinicalTrials.gov (identifier NCT00535665). All relevant documents were approved by the ethical review committee of Beijing Centers for Diseases Control and Prevention, and all participants provided written informed consent.

Vaccine. The vaccine was an inactivated, whole-virion H5N1 vaccine using recombinant strain NIBRG-14 as seed virus, which was a 2:6 reassortant between A/Vietnam/1194/2004 (H5N1) and A/PR/8/34 (H1N1) [15, 16]. The NIBRG-14 strain was prepared by the UK National Institute for Biological Standards and Control using reverse genetics technology and was recommended as a prototypical influenza pandemic vaccine strain by the European Union Committee for Medicinal Products for Human Use (EU CHMP) [17].

The vaccine was produced in embryonated hens' eggs and formulated with aluminum hydroxide as reported previously [12]. A 0.5-mL dose (monodose in vial) contained 5, 10, or 15 μg of H5N1 antigen without preservative (lots 20070103, 2007012, and 20070101, respectively). Alum (0.25 mg per dose) was already mixed in the vial (i.e., not added at bedside).

Two vaccination regimens were used. The vaccines given on days 0 and 28 were subjected to randomization. A randomized block design was used with a block size of 6 (2:2:2) to maintain balance in the 3 dosages. The randomized vaccines were blindly labeled with sequential numbers. The vaccines (10 μg only) given on days 0 and 14 regimen were openly labeled.

Procedures. The trial profile is shown in figure 1. Among 402 participants enrolled, 301 individuals were stratified by sex and age groups (84, 72, 72, and 73 participants from the age groups of 18–30, 31–40, 41–50, and 51–60 years, respectively) and randomly assigned to 1 of the 3 dosage groups (5, 10, and 15 μg), with 100 or 101 participants per group to receive 2 doses of blind-labeled vaccines 28 days apart. The 101 individuals received 2 doses of openly labeled 10-μg vaccines 14 days apart. The vaccines were administered intramuscularly into the deltoid muscle. Serum samples were collected before each vaccination and 14 and 28 days after the second dose.

Figure 1
View larger version:
Figure 1

Profile of a trial of pandemic influenza (H5N1) vaccine

Diary cards were used to record adverse events, including local and systematic events. The diameters of any erythema, swelling, induration, and rash at the injection site were determined by investigators, and axillary temperatures were measured by participants. The adverse events recorded by participants were reviewed by investigators. All adverse events were graded by a standard scale [18].

Serologic assays. All samples were assayed blindly by hemagglutination inhibition (HI) and microneutralization (MN) methods against the homologous NIBRG-14 strain (clade 1). The HI assays were performed in accordance with established procedures using turkey erythrocytes [19], which were used previously in assessment of H5, H9, and H2 vaccines [12, 14, 20]. In brief, samples were treated with cholera filtrate at 36°C for 16 h and then tested in 2-fold dilution starting with a 1:10 dilution. The MN assays were conducted according to a previous report [20]. In brief, 2-fold dilutions of heat-inactivated samples were mixed with NIBRG-14 and incubated at 33°C for 60 min and then added to Madin-Darby canine kidney cells and cultured at 33°C for 5 days. Hemagglutination activity in the supernatant was tested, and the MN titer was calculated by the Reed-Muench method [21].

A subset that included 156 participants was selected blindly for cross-reaction assays before the beginning of titration against homologous NIBRG-14, who all completed the visit schedule and were from 1 of the 3 dosage groups for the regimen given on days 0 and 28. To maintain balance in the 3 dosages, the 156 participants (52 per dosage) were picked by block (block size, 6) (i.e., 26 blocks were picked, which were equally distributed by age and sex, with 48, 36, 36, and 36 participants from the age groups of 18–30, 31–40, 41–50, and 51–60 years, respectively, with a 1:1 sex ratio in each group). The cross-reactivity was assayed against 3 heterologous H5N1 strains, including IBCDC-RG2 (A/Indonesia/5/2005-A/PR/8/34, clade 2.1), NIBRG-23 (A/turkey/Turkey/1/2005-A/PR/8/34, clade 2.2), and IBCDC-RG5 (A/Anhui/1/2005-A/PR/8/34, clade 2.3), which were reassortants derived by reverse genetics and recommended by the World Health Organization as H5N1 candidate vaccine viruses [22]. The MN cross-reaction was not performed against NIBRG-23, because the quantity of the samples was too low. For simplicity, the 4 strains are named Vietnam, Indonesia, Turkey, and Anhui in this article.

The HI and MN titers <1:10 were recorded as 1:5. All samples were assayed in duplicate and double-checked by 2 persons (C.-G.L. and Q.G.).

Statistical analysis. Our planned sample size of 400, with 100 participants per group, was chosen on the basis of the lower limit of 2-sided 95% CIs of HI seroconversion rate in a previous phase I trial (56% in the 10-μg group) [12] and the criteria (40%) issued by the US Food and Drug Administration (FDA) [23]. To detect a 16% increase (56% vs. 40%), at least 74 assessable participants per group were needed to provide 80% power and a 2-sided significance level of .05. Our target was to enroll 100 participants per group to reach at least 95 assessable individuals, which could detect a 16% increase in the lower limit of the 95% CI with 89% power and a .05 significance level.

The prespecified primary immunologic end point was the HI seroconversion rate after 2 doses. Participants were considered to have undergone HI seroconversion when their titers were <1:10 before vaccination and a ⩾1:40 after vaccination or their titers were ⩾1:10 before vaccination and they had at least a 4-fold increase after vaccination according to EU CHMP [24]. Other end points of HI included geometric mean titer (GMT), postvaccination-to-prevaccination GMT ratio, and se-ro-pro-tec-tion rate (⩾1:40). The MN titers were expressed by GMT, seroconversion rate (arbitrarily defined similar to that of HI), GMT ratio, and proportion of participants having a titer ⩾1:40.

The incidence of adverse events was expressed in terms of the number and proportion of individuals reporting adverse events. Pearson's χ2 test or Fisher's exact test was used to compare relevant groups. The HI and MN titer distributions were described with reverse cumulative distribution curves. Spearman's correlation coefficient was used to assess the correlation between the HI and MN titers. Statistical analysis was performed by intension to treatment. The significance level was .05 (2-sided).

Previous SectionNext Section

Results

Among 402 participants enrolled, 301 participants were randomly assigned to receive 2 doses of 5, 10, or 15 μg of the vaccine 28 days apart. The remaining 101 participants received 2 doses of 10 μg of vaccine 14 days apart. The demographic details are summarized in table 1. No statistical differences were found in age and sex in the 4 vaccination groups. All participants received the first dose, completed the safety observation, and were included in safety set. Thirteen participants withdrew before the second dose because of noncompliance with the schedule. The 389 participants who received 2 doses, attended all visits, and donated the planned 4 blood samples were included in the per protocol set. The safety set ( n=402 ) was used for safety analysis and the per protocol set ( n=389 ) for immunogenicity analysis.

Figure 2
View larger version:
Figure 2

Reverse cumulative distribution curve of titers against the recombinant A/Vietnam/1194/2004 strain (NIBRG-14), as determined by the hemagglutination inhibition assay (A) and the microneutralization assay (B) 14 days after administration of the second dose.

Table 1
View larger version:
Table 1

Demographic characteristics of the study population.

Before vaccination, 6 of 389 participants included in immunogenicity analysis showed a detectable (⩾1:10) HI titer, 2 of whom also had a detectable (⩾1:10) MN titer. The GMTs before vaccination were statistically similar among the 4 groups ( P=.331 and .082 for HI and MN, respectively).

All vaccine formulations were well tolerated, without immediate allergic reactions or serious adverse events. The adverse reactions are given in table 2. A total of 136 participants (34%) reported adverse reactions, all of which resolved within 72 h. The incidences of adverse reactions did not show statistic differences ( P=.080 ) among the 4 groups. The adverse reactions after the second dose were remarkably fewer than after the first dose (10% vs. 31%; P<.001 ).

Table 2
View larger version:
Table 2

Participants with adverse reactions after 1 or both vaccinations.

The incidences of local and systemic reactions were 23% and 24%, respectively (table 2). Pain at the injection site was the most common local reaction (22%), followed by swelling (2%) and induration (2%). Other local reactions were less common. The incidences of pain, swelling, and induration did not show statistical differences among the 4 groups ( P=.220 , .528, and .406, respectively). Fatigue was the most common systemic reaction (10%), followed by fever (8%) and headache (8%). Most of the fatigue and headache were mild (8% and 7%, respectively) or moderate (2% and 1%, respectively). All of the fever was mild (temperature, 37.1°C–37.5°C; 5%) or moderate (temperature, 37.6°C–39.0°C; 4%). Except for the incidence of fever, which was higher in the 15-μg group, the incidences of fatigue and headache did not show statistical differences among the 4 groups ( P=.960 and .739, respectively).

The results of the HI assays against the homologous Vietnam strain are summarized in table 3 and figure 2A . A clear dose-dependent relationship was observed in all 3 groups of subjects who received vaccine on days 0 and 28. Fourteen days after 2 doses of the 15-μg vaccine, a GMT of 1:91 and 90% seroconversion and seroprotection rates were achieved. Fourteen days after 2 doses, the 10-μg vaccine induced a GMT of 1:63 and 78% seroconversion and seroprotection rates for persons who received the vaccine on days 0 and 28, in contrast to 1:42 and 55% for persons who received the vaccine on days 0 and 14 ( P=.001 ). However, the difference between the 2 regimens was statistically less significant at 28 days after 2 doses ( P=.109 and .049).

Table 3
View larger version:
Table 3

Hemagglutination inhibition antibody response against the homologous Vietnam strain.

The MN assays against the Vietnam strain also showed a similar dose-dependent relationship, time profile, and regimen effect (table 4 and figure 2B ). Fourteen days after receipt of 2 doses, GMTs of 1:97–1:222 were achieved in the 4 groups, and most participants experienced seroconversion (91%–100%) and developed a titer of ⩾1:40 (94%–100%). The highest MN titer was detected in the 15-μg group. In general, receipt of vaccine on days 0 and 28 induced a higher response than did receipt on days 0 and 14. Spearman's correlation coefficients between the HI and MN titers were 0.784–0.864 in the 4 groups, with an average correlation coefficient of 0.821.

Table 4
View larger version:
Table 4

Microneutralization antibody response against the homologous Vietnam strain.

The HI cross-reactions showed 65% seroconversion and se-ro-pro-tec-tion rates against the heterologous Indonesia and Anhui strains after 2 doses of the 10-μg vaccine, in contrast to the 73% seroconversion and seroprotection rates against the homologous Vietnam strain (table 5). The MN cross-reactions showed that after 2 doses of the 10-μg vaccine, 90%, 96%, and 85% of participants experienced seroconversion and 96%, 98% and 87% of participants had a titer of ⩾1:40 against the Vietnam, Indonesia, and Anhui strains, respectively. Although the MN titer against the Indonesia strain was statistically higher than that against the Vietnam strain ( P=.017 ), the MN seroconversion rates and proportions of participants who had a titer ⩾1:40 were statistically similar ( P=.434 and .558, respectively) between the 2 strains. Obvious cross-reactions were also detected against Indonesia and Anhui strains in the 5- and 15-μg groups, for which 29% and 75% (for HI) and 58% and 92% (for MN) of participants experienced seroconversion after receipt of 2 doses (data not shown), respectively. However, the cross-reactions against the Turkey strain were much weaker (table 5).

Table 5
View larger version:
Table 5

Cross-reactivity against H5N1 drifted strains at 28 days after 2 doses of the 10-μg vaccine (n = 52).

Previous SectionNext Section

Discussion

Whole-virion seasonal influenza vaccines are generally believed to be more reactogenic than their split-virion counterparts. However, our results indicated that the inactivated, aluminum-adjuvanted, whole-virion H5N1 vaccine prepared from NIBRG-14 had a good safety profile in adults. Most adverse reactions were mild or moderate and resolved within 24 h. There was no evidence that dosage affected reactogenicity. Thirteen participants withdrew from the study before they had received second dose, none because of adverse reactions. In view of the high risk caused by the H5N1 virus and the substantial benefit of an effective vaccine, the safety profile of the H5N1 vaccine is acceptable. Further study is ongoing to evaluate the whole-virion H5N1 vaccine in younger participants.

Corresponding well with the results of the phase I trial [12], we confirm herein that 2 doses of whole-virion H5N1 vaccine were needed and that both the 10- and 15-μg doses met EU CHMP criteria for GMT ratio (>2.5), seroconversion rate (>40%), and seroprotection rate (>70%) of HI antibody [15, 24]. For the licensure of H5N1 vaccine, the FDA released more-stringent criteria for HI seroconversion rate (lower limit of 95% CI, ⩾40%) and seroprotection rate (lower limit of 95% CI, ⩾70%) [23]. After administration of 2 doses, the 10-μg dose (both 2 regimens) met the FDA criterion for seroconversion rate and the 15-μg dose met the 2 FDA criteria.

In the context of the immunological criteria of pandemic vaccines, HI and MN assays are variable and poorly standardized, and no correlation of protection is established, making it challenging to use them for licensure. The protection criteria of ⩾1:40 for the HI titer, which is applied to the evaluation of seasonal influenza vaccines, may not be valid for pandemic influenza vaccines. Alternative criteria assumed to correlate with protection in a pandemic situation may need to be justified and redefined. The development of antibody standards is important. However, with no other evidence-based criteria at present, the EU CHMP anticipated that pandemic candidate vaccines should at least be able to elicit responses to meet all 3 of the criteria set for seasonal vaccines. It seems reasonable to assume that the fulfillment of the current 3 criteria is likely to be predictive of clinical benefit.

An obvious dose-response relationship was seen. A dose of 15 μg induced a higher response than the 10- and 5-μg doses did. However, compared with the 10-μg dose, the 15-μg dose induced 15% higher (from 78% to 90%) seroconversion and seroprotection rates, with the cost of an additional 50% antigen content. Taking into account the cost-effectiveness ratio and the fact that the 10-μg dose elicited a response that met all 3 EU CHMP criteria, it is reasonable to consider that the 10-μg dose would be more effective.

Administration of the vaccine on days 0 and 21 and on days 0 and 28 has been studied previously [10–13]. However, the effect of the interval of 2 vaccinations on the immunogenicity and safety remains unsettled. Our study found that the interval of 2 vaccinations did not significantly influence the safety profile but affected the immune response. To the best of our knowledge, this is the first study of H5N1 vaccines to compare 2 vaccination regimens. Higher immune responses were observed when persons received vaccine doses 28 days apart. However, receipt of vaccine on days 0 and 14 can induce satisfactory immune response in a shorter interval (i.e., more quickly), which would be the preferred choice for the immunologically naive persons who are about to encounter the H5N1 virus. In addition, when used as emergent vaccination for a high-risk population, the speed of response would be an important consideration of public health planners. Administration of vaccine on days 0 and 14 would be more suitable in those situations.

Cross-reactivity against drifted strains is a common concern for H5N1 vaccine, because H5N1 viruses have genetically and antigenically distinct groups. Moreover, H5N1 viruses are undergoing antigenic drift, further complicating vaccine development. Good cross-reactivity may make a H5N1 vaccine acceptable in more regions. Immunologically naive populations may benefit from the priming of the vaccine even if the circulating virus in the next influenza pandemic is not closely matched to the vaccine virus. Our results showed that the whole-virion vaccine prepared by the recombinant Vietnam strain induced cross-reactivity against H5N1 strains from different phylogenic clades. Response against the Indonesia and Anhui strains was comparable to that against the Vietnam strain. However, the cross-reactive response against the Turkey strain was relatively lower. A previous trial with an oil-in-water emulsion–adjuvanted, split-virion vaccine showed obvious cross-reactivity against the recombinant Indonesia strain in MN, but this was not demonstrated with HI assays [13]. The cross-reactivity against the recombinant Indonesia strain presented herein appeared to be better than that induced by an aluminum-adjuvanted split vaccine [25], which might be because of the whole-virion vaccine used in this study. It has been suggested that underestimation of cross-reactivity could result from use of reverse-genetic viruses instead of wild-type viruses in MN assays [25]. We did not use wild-type viruses because of unavailable Containment Level 4 containment. If this suggestion is confirmed, the cross-reactivity of the whole-virion vaccine would be more significant when used with wild-type strains.

During a pandemic, the demand for vaccines will far outstrip the manufacturing capacity, which is why the World Health Organization encourages investigation into antigen-sparing strategies, including the use of adjuvants and whole-virion vaccines [26]. Combined with previous phase I trial data, the results presented herein show that the aluminum-adjuvanted, whole-virion H5N1 vaccine is of good immunogenicity, safety, and cross-reactivity, which makes the vaccine a satisfactory alternative for deployment and stockpile before the next pandemic outbreak.

Previous SectionNext Section

Acknowledgments

We appreciate the UK National Institute for Biological Standards and Control and the US Centers for Disease Control and Prevention for kindly providing the virus strains and reference standards.

Financial support. Ministry of Science and Technology of the People's Republic of China (2004BA519A66), Beijing Municipal Science & Technology Commission (Z07000200540702), and Sinovac Biotech.

Manuscript preparation. Sinovac Biotech had a role in study design, monitoring, interpretation of data, and writing of the report.

Potential conflicts of interest. N.W., Y.Z.Q., Y.L., J.T.C., S.S.D., Q.G., X.M.Z., and W.D.Y. are employed by Sinovac Biotech. All other authors: no conflicts.

Previous SectionNext Section

Footnotes

  • ↵a J.W. and H.-H.F. contributed equally to the work.

  • Received October 14, 2008.
  • Accepted December 16, 2008.
Previous Section
 

References

  1. ↵
    1. Claas EC,
    2. Osterhaus AD,
    3. van Beek R,
    4. et al
    . Human influenza A H5N1 virus related to a highly pathogenic avian influenza virus. Lancet 1998;351:472-7.
    CrossRefMedlineWeb of Science
  2. ↵
    World Health Organization. H5N1 avian influenza: timeline of major events. Geneva: World Health Organization. 2008. Available at: http://www.who.int/entity/csr/disease/avian_influenza/timeline2008_04_09.pdf. Accessed 4 May 2008.
  3. ↵
    World Health Organization. Cumulative number of confirmed human cases of avian influenza A/(H5N1) reported to WHO. 2008. Available at: http://www.who.int/csr/disease/avian_influenza/country/cases_table_2008_06_19/en/index.html. Accessed 4 July 2008.
  4. ↵
    1. Ungchusak K,
    2. Auewarakul P,
    3. Dowell SF,
    4. et al
    . Probable person-to-person transmission of avian influenza A (H5N1). N Engl J Med 2005;352:333-40.
    CrossRefMedlineWeb of Science
  5. ↵
    World Health Organization Global Influenza Program Surveillance Network. Evolution of H5N1 avian influenza viruses in Asia. Emerg Infect Dis 2005;11:1515-21.
    MedlineWeb of Science
  6. ↵
    1. Wood JM
    . Selection of influenza vaccine strains and developing pandemic vaccines. Vaccine 2002;20:40-4.
  7. ↵
    1. Nicholson KG,
    2. Colegate AE,
    3. Podda A,
    4. et al
    . Safety and antigenicity of non-adjuvanted and MF59-adjuvanted influenza A/Duck/Singapore/97 (H5N3) vaccine: a randomised trial of two potential vaccines against H5N1 influenza. Lancet 2001;357:1937-43.
    CrossRefMedlineWeb of Science
  8. ↵
    1. Stephenson I,
    2. Nicholson KG,
    3. Glück R,
    4. 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;362:1959-66.
    CrossRefMedlineWeb of Science
    1. Treanor JJ,
    2. Wilkinson BE,
    3. Masseoud F,
    4. et al
    . Safety and immunogenicity of a recombinant hemagglutinin vaccine for H5 influenza in humans. Vaccine 2001;19:1732-7.
    CrossRefMedlineWeb of Science
  10. ↵
    1. Treanor JJ,
    2. Campbell JD,
    3. Zangwill KM,
    4. Rowe T,
    5. Wolff M
    . Safety and immunogenicity of an inactivated subvirion influenza A (H5N1) vaccine. N Engl J Med 2006;354:1343-51.
    CrossRefMedlineWeb of Science
    1. Bresson JL,
    2. Perronne C,
    3. Launay O,
    4. et al
    . Safety and immunogenicity of an inactivated split-virion influenza A/Vietnam/1194/2004 (H5N1) vaccine: phase 1 randomized trial. Lancet 2006;367:1657-64.
    CrossRefMedlineWeb of Science
  12. ↵
    1. Lin J,
    2. Zhang J,
    3. Dong X,
    4. et al
    . Safety and immunogenicity of an inactivated adjuvanted whole-virion influenza A (H5N1) vaccine: a phase I randomised controlled trial. Lancet 2006;368:991-7.
    CrossRefMedlineWeb of Science
  13. ↵
    1. Leroux-Roels I,
    2. Borkowski A,
    3. Vanwolleghem T,
    4. et al
    . Antigen sparing and cross-reactive immunity with an adjuvanted rH5N1 prototype pandemic influenza vaccine: a randomised controlled trial. Lancet 2007;370:580-9.
    CrossRefMedlineWeb of Science
  14. ↵
    1. Hehme N,
    2. Engelmann H,
    3. Kunzel W,
    4. Neumeier E,
    5. Sanger R
    . Pandemic preparedness: lessons learnt from H2N2 and H9N2 candidate vaccines. Med Microbiol Immunol 2002;191:203-8.
    CrossRefMedline
  15. ↵
    1. Wood JM,
    2. Robertson JS
    . From lethal virus to life-saving vaccine: developing inactivated vaccines for pandemic influenza. Nat Rev Microbiol 2004;2:842-7.
    CrossRefMedlineWeb of Science
  16. ↵
    1. Nicolson C,
    2. Major D,
    3. Wood JM,
    4. Robertson JS
    . Generation of influenza vaccine viruses on Vero cells by reverse genetics: an H5N1 candidate vaccine strain produced under a quality system. Vaccine 2005;23:2943-52.
    CrossRefMedlineWeb of Science
  17. ↵
    European Committee for Proprietary Medicinal Products. Guideline on dossier structure and content for pandemic influenza vaccine marketing authorisation application (CPMP/VEG/4717/03). London, England: European Agency for the Evaluation of Medicinal Products. 2004.
  18. ↵
    Division of Microbiology and Infectious Diseases. Adult toxicity table. Available at: http://www3.niaid.nih.gov/NR/rdonlyres/401FA10C-8DF2-4162-8B21-2554129F4294/0/dmidadulttox.doc. Accessed 4 January 2008.
  19. ↵
    1. Kendal AP,
    2. Pereira MS,
    3. Skehel J
    . Concepts and procedures for laboratory based influenza surveillance. Geneva, Switzerland: World Health Organization. 1982.
  20. ↵
    1. Hehme N,
    2. Engelmann H,
    3. Kuenzel W,
    4. Neumeier E,
    5. Sanger R
    . Immunogenicity of a monovalent, aluminum-adjuvanted influenza whole virus vaccine for pandemic use. Virus Res 2004;103:163-71.
    CrossRefMedlineWeb of Science
  21. ↵
    1. Reed LJ,
    2. Muench HA
    . A simple method of estimating fifty percent endpoints. Am J Hyg 1938;27:493-0000.
  22. ↵
    WHO. Antigenic and genetic characteristics of H5N1 viruses and candidate H5N1 vaccine viruses developed for potential use as pre-pandemic vaccines. 2008. Available at: http://www.who.int/csr/disease/avian_influenza/guidelines/summaryH520070403.pdf. Accessed 26 March 2008.
  23. ↵
    US Food and Drug Administration. Guidance for industry: clinical data needed to support the licensure of pandemic influenza vaccines. 2008. Available at: http://www.fda.gov/cber/gdlns/panfluvac.htm. Accessed 4 January 2008.
  24. ↵
    European Committee for Proprietary Medicinal Products. Note for guidance on harmonisation of requirements for influenza vaccines (CPMP/BWP/214/96). London: European Agency for the Evaluation of Medicinal Products. 1997.
  25. ↵
    1. Höschler K,
    2. Gopal R,
    3. Andrews N,
    4. et al
    . Cross-neutralisation of antibodies elicited by an inactivated split-virion influenza A/Vietnam/1194/2004 (H5N1) vaccine in healthy adults against H5N1 clade 2 strains. Influenza Other Respir Viruses 2008;1:199-206.
    CrossRefWeb of Science
  26. ↵
    World Health Organization. Development and evaluation of influenza pandemic vaccines: report of WHO expert meeting. Initiative for Vaccine Research, Global Influenza Programme. 2008. Available at: http://www.who.int/vaccine_research/documents/Report%20021105.pdf. Accessed 4 January 2008.
| Table of Contents

This Article

  1. Clin Infect Dis. (2009) 48 (8): 1087-1095. doi: 10.1086/597401
  1. AbstractFree
  2. » Full Text (HTML)Free
  3. Full Text (PDF)Free

Classifications

Share

  1. Email this article

Navigate This Article

Current Issue

  1. March 1, 2012 54 (5)
  1. Clinical Infectious Diseases
  1. Alert me to new issues

Most