Vaccinology in the post-COVID-19 era.

The COVID-19 pandemic is a shocking reminder of how our world would look in the absence of vaccination. Fortunately, new technologies, the pace of understanding new and existing pathogens, and the increased knowledge of the immune system allow us today to develop vaccines at an unprecedented speed. Some of the vaccine technologies that are fast-tracked by the urgency of COVID-19 may also be the answer for other health priorities, such as antimicrobial resistance, chronic infections, and cancer, that the post-COVID-19 world will urgently need to face. This perspective analyzes the way COVID-19 is transforming vaccinology and the opportunities for vaccines to have an increasingly important role in health and well-being.

H5N1 influenza vaccine formulated with AS03 A induces strong cross-reactive and polyfunctional CD4 T-cell responses.

OBJECTIVE: Adjuvantation of an H5N1 split-virion influenza vaccine with AS03(A) substantially reduces the antigen dose required to produce a putatively protective humoral response and promotes cross-clade neutralizing responses. We determined the effect of adjuvantation on antibody persistence and B- and T-cell-mediated immune responses. METHODS: Two vaccinations with a split-virion A/Vietnam/1194/2004 (H5N1, clade 1) vaccine containing 3.75-30 µg hemagglutinin and formulated with or without adjuvant were administered to groups of 50 volunteers aged 18-60 years. RESULTS: Adjuvantation of the vaccine led to better persistence of neutralizing and hemagglutination-inhibiting antibodies and higher frequencies of antigen-specific memory B cells. Cross-reactive and polyfunctional H5N1-specific CD4 T cells were detected at baseline and were amplified by vaccination. Expansion of CD4 T cells was enhanced by adjuvantation. CONCLUSION: Formulation of the H5N1 vaccine with AS03(A) enhances antibody persistence and induces stronger T- and B-cell responses. The cross-clade T-cell immunity indicates that the adjuvanted vaccine primes individuals to respond to either infection and/or subsequent vaccination with strains drifted from the primary vaccine strain.

AS03(A)-Adjuvanted influenza A (H1N1) 2009 vaccine for adults up to 85 years of age.

BACKGROUND: Vaccination of high-risk groups was started shortly after the emergence of the influenza A (H1N1)2009 pandemic virus. METHODS: Healthy adults were enrolled into 2 age strata: 18-60 years and 160 years, and received monovalent influenza vaccine containing 3.75 microg of A/California/2009 (H1N1) hemagglutinin antigen, adjuvanted with AS03A. Hemagglutination inhibition assay-based antibody titers against H1N1 vaccine were assessed after 1 vaccine dose(primary endpoint), after which subjects were randomized 1:1 to receive no further vaccination or a second dose.Immunogenicity endpoints were European licensure criteria for influenza vaccines. Exploratory analyses assessed the effect of previous seasonal influenza vaccination on responses to the H1N1 vaccine. RESULTS: Licensure criteria for immunogenicity were fulfilled after 1 dose of H1N1 vaccine (N=240). For subjects 18-60 years of age, previous vaccination against seasonal influenza within the preceding 2 seasons resulted in significantly lower geometric mean titers (adjusted for baseline antibody titer) after 1 or 2 doses of H1N1 vaccine (P <.001 and P=.003, respectively). Transient mild or moderate injection-site pain was reported by 87.5%and 65.0% of subjects 18-60 years of age and >60 years of age, respectively, after the first dose, and in 63% of subjects overall after the second dose. CONCLUSIONS: A single dose of 3.75 microg hemagglutinin antigen, AS03A-adjuvanted H1N1 2009 vaccine was immunogenic and well tolerated in adults. In exploratory analyses (of subjects 18-60 years of age), postvaccination antibody titers were lower in subjects who had previously received seasonal influenza vaccination, compared with those who had not. This phenomenon warrants further investigation. CLINICAL TRIALS REGISTRATION: NCT00968526.

Developing Vaccines for SARS-CoV-2 and Future Epidemics and Pandemics: Applying Lessons from Past Outbreaks.

The COVID-19 pandemic is a stark reminder of the heavy toll that emerging infectious diseases (EIDs) with epidemic and pandemic potential can inflict. Vaccine development, scale-up, and commercialization is a long, expensive, and risky enterprise that requires substantial upfront planning and offers no guarantee of success. EIDs are a particularly challenging target for global health preparedness, including for vaccine development. Insufficient attention has been given to challenges, lessons learned, and potential solutions to support and sustain vaccine industry engagement in vaccine development for EIDs. Drawing from lessons from the most recent Ebola epidemic in the Democratic Republic of the Congo, as well as the 2009 H1N1 influenza, 2014-2016 Ebola, and 2015-16 Zika outbreaks preceding it, we offer our perspective on challenges facing EID vaccine development and recommend additional solutions to prioritize in the near term. The 6 recommendations focus on reducing vaccine development timelines and increasing business certainty to reduce risks for companies. The global health security community has an opportunity to build on the current momentum to design a sustainable model for EID vaccines.

Sustainable vaccine development: a vaccine manufacturer's perspective.

Vaccination remains the most cost-effective public health intervention after clean water, and the benefits impressively outweigh the costs. The efforts needed to fulfill the steadily growing demands for next-generation and novel vaccines designed for emerging pathogens and new indications are only realizable in a sustainable business model. Vaccine development can be fast-tracked through strengthening international collaborations, and the continuous innovation of technologies to accelerate their design, development, and manufacturing. However, these processes should be supported by a balanced project portfolio, and by managing sustainable vaccine procurement strategies for different types of markets. Collectively this will allow a gradual shift to a more streamlined and profitable vaccine production, which can significantly contribute to the worldwide effort to shape global health.

Towards an evidence based approach for the development of adjuvanted vaccines.

In the last two decades, several vaccines formulated with a new generation of adjuvants have been licensed or approved to target diseases such as influenza, hepatitis B, cervical cancer, and malaria. These new generation adjuvants appear to work by delivering a localized activation signal to the innate immune system, which in turn promotes antigen-specific adaptive immunity. Advances in understanding of the innate immune system together with high-throughput discovery of synthetic immune potentiators are now expanding the portfolio of new generation adjuvants available for evaluation. Meanwhile, omics and systems biology are providing molecular benchmarks or signatures to assess vaccine safety and effectiveness. This accumulating knowledge and experience raises the prospect that the future selection of the right antigen/adjuvant combination can be more evidence based and can speed up the clinical development program for new adjuvanted vaccines.

Comment on "CD4+ T cell autoimmunity to hypocretin/orexin and cross-reactivity to a 2009 H1N1 influenza A epitope in narcolepsy".

Scientists from the maker of the Pandemrix vaccine for influenza present their views on results linking epitopes in influenza and narcolepsy.

Narcolepsy and A(H1N1)pdm09 vaccination: shaping the research on the observed signal.

Epidemiological data from several European countries suggested an increased risk of the chronic sleep disorder narcolepsy following vaccination with Pandemrix(™), an AS03-adjuvanted, pandemic A(H1N1)pdm09 influenza vaccine. Further research to investigate potential associations between Pandemrix™ vaccination, A(H1N1)pdm09 influenza infection and narcolepsy is required. Narcolepsy is most commonly caused by a reduction or absence of hypocretin produced by hypocretin-secreting neurons in the hypothalamus, and is tightly associated with HLA-II DQB1*06:02. Consequently, research focusing on CD4(+) T-cell responses, building on the hypothesis that for disease development, T cells specific for antigen(s) from hypocretin neurons must be activated or reactivated, is considered essential. Therefore, the following key areas of research can be identified, (1) characterization of hypothetical narcolepsy-specific auto-immune CD4(+) T cells, (2) mapping epitopes of such T cells, and (3) evaluating potential mechanisms that would enable such cells to gain access to the hypothalamus. Addressing these questions could further our understanding of the potential links between narcolepsy and A(H1N1)pdm09 vaccination and/or infection. Of particular interest is that any evidence of a mimicry-based mechanism could also explain the association between narcolepsy and A(H1N1)pdm09 influenza infection.

Seeking help: B cells adapting to flu variability.

The study of influenza vaccines has revealed potential interactions between preexisting immunological memory and antigenic context and/or adjuvantation. In the face of antigenic diversity, the process of generating B cell adaptability is driven by cross-reactive CD4 memory cells, such as T follicular helper cells from previous infections or vaccinations. Although such "helped" B cells are capable of adapting to variant antigens, lack of CD4 help could lead to a suboptimal antibody response. Collectively, this indicates an interplay between CD4 T cells, adjuvant, and B cell adaptability.

Long-term persistence of humoral and cellular immune responses induced by an AS03A-adjuvanted H1N1 2009 influenza vaccine: an open-label, randomized study in adults aged 18-60 years and older.

This manuscript presents data on the persistence of Hemagglutination Inhibition (HI) immune response against the A/California/7/2009 strain, six and 12 mo after adults received one dose (n = 138) or two doses (n = 102; 21 d apart) of a 3.75 µg Hemagglutinin antigen AS03-adjuvanted H1N1 2009 vaccine (NCT00968526). Two hundred forty subjects (18-60 y: 120;>60 y: 120) were vaccinated. Immunogenicity end points were based on the European licensure criteria for pandemic influenza vaccines. Exploratory analyses assessed the cell-mediated immune response (CMI) up to Month 12 and the influence of previous influenza vaccination on persistence of immune response. At Month 6, the CHMP criteria were met in subjects aged 18-60 y who received one or two vaccine doses and in subjects aged>60 y who received two vaccine doses. At Month 12, the CHMP criteria were met only in subjects aged 18-60 y who received two vaccine doses. Persistence of HI immune response against the vaccine strain was higher in subjects without prior influenza vaccination. Exploratory analyses showed that two doses of the H1N1 2009 vaccine induced persistence of H1N1-specific CD4+ T cells up to Month 6 and memory B cells up to Month 12. In conclusion, HI immune responses persisted up to 12 mo after vaccination with one-dose and two-dose regimens of the AS03-adjuvanted 3.75 µg HA H1N1 2009 pandemic influenza vaccine, although not all three CHMP guidance criteria for both groups were met at Month 6 and Month 12. The CD4+ T cell and B cell responses also persisted up to Month 12.

Effect on cellular and humoral immune responses of the AS03 adjuvant system in an A/H1N1/2009 influenza virus vaccine administered to adults during two randomized controlled trials.

The influence of AS03(A), a tocopherol oil-in-water emulsion-based adjuvant system, on humoral and cell-mediated responses to A/California/7/2009 H1N1 pandemic vaccine was investigated. In two observer-blind studies, a total of 261 healthy adults aged 18 to 60 years were randomized to receive either AS03(A)-adjuvanted H1N1 vaccine containing 3.75 µg hemagglutinin (HA) or nonadjuvanted H1N1 vaccine containing 15 or 3.75 µg HA on days 0 and 21. Hemagglutination inhibition (HI) antibody and T-cell responses were analyzed up to day 42. A first dose of AS03(A)-adjuvanted vaccine (3.75 µg HA) or nonadjuvanted vaccine (15 µg HA) induced HI responses of similar magnitudes that exceeded licensure criteria (e.g., 94 to 100% with titers of ≥ 40). A lower response following 3.75 µg HA without adjuvant was observed (73% with titers of ≥ 40). Following a second dose, geometric mean HI titers at day 42 were higher for AS03(A)-adjuvanted vaccine (636 and 637) relative to nonadjuvanted vaccine (341 for 15 µg HA and 150 for 3.75 µg HA). Over the 42-day period, the increase in frequency of A/H1N1/2009-specific CD4⁺ T cells was significantly higher in the adjuvanted group than in the nonadjuvanted group. There was no evidence of correlation between baseline CD4⁺ T-cell frequencies and day 21 HI antibody titers, while there was some correlation (R = 0.35) between day 21 CD4⁺ T-cell frequencies and day 42 HI titers. AS03(A) adjuvant enhanced the humoral and CD4⁺ T-cell-mediated responses to A/H1N1/2009 vaccine. Baseline A/H1N1/2009-specific CD4⁺ T-cell frequencies did not predict post-dose 1 antibody responses, but there was some correlation between post-dose 1 CD4⁺ T-cell frequencies and post-dose 2 antibody responses.

Longevity of the protective immune response induced after vaccination with one or two doses of AS03A-adjuvanted split H5N1 vaccine in ferrets.

It is crucial that a safe and effective pandemic vaccine be rapidly available to combat a new pandemic threat. In this study we investigated the magnitude and persistence of the protective efficacy induced by one or two doses (3.75 µg HA/dose) of AS03(A)-adjuvanted H5N1 A/Indonesia/5/05 split vaccine in a lethal ferret challenge model. All ferrets that received at least one dose of adjuvanted vaccine 4 weeks before homologous challenge survived and showed reduced or undetectable virus replication in the lungs and the upper airways. Ferrets receiving two doses of adjuvanted vaccine 19 and 16 weeks before the challenge also showed high level of protection from replication in the lungs and the upper airways, albeit with only 83% survival. Animals in the control groups (non-adjuvanted vaccine or saline) and animals immunized with one dose of adjuvanted vaccine administered 10 or 16 weeks before challenge showed only 17-33% survival rate after challenge. In conclusion, our observations support the possibility that a single dose of AS03(A)-adjuvanted H5N1 split vaccine can offer a rapid and short term but partial protection against disease. A second dose of the adjuvanted vaccine, which can be given with a flexible injection schedule, was shown to be essential to induce appreciable levels of antibodies and long-term protection.

Pandemic H1N1 vaccine requires the use of an adjuvant to protect against challenge in naïve ferrets.

In the context of an A/H1N1 influenza pandemic situation, this study demonstrates that heterologous vaccination with an AS03-adjuvanted 2008/2009 seasonal trivalent and pandemic H5N1 monovalent split vaccine conferred partial protection in influenza-naïve ferrets after challenge with the influenza pandemic H1N1 A/The Netherlands/602/09 virus. Further, unlike saline control and non-adjuvanted vaccine, it was shown that immunization of naïve ferrets with an AS03-adjuvanted pandemic H1N1 A/California/7/09 influenza split vaccine induced increased antibody response and enhanced protection against the challenge strain, including significant reduction in viral shedding in the upper respiratory tract and reduced lung pathology post-challenge. These results show the need for vaccination with the adjuvanted vaccine to fully protect against viral replication and influenza disease in unprimed ferrets.

Priming with AS03 A-adjuvanted H5N1 influenza vaccine improves the kinetics, magnitude and durability of the immune response after a heterologous booster vaccination: an open non-randomised extension of a double-blind randomised primary study.

An influenza vaccine with cross-immunogenic potential could play a key role in pandemic mitigation by promoting a rapid immune response to infection and/or subsequent vaccination with strains drifted from the primary vaccine strain. Here we assess the role of AS03(A) (an oil-in-water emulsion based Adjuvant System containing tocopherol) in this prime-boost concept using H5N1 as a model shift influenza antigen. In this open, non-randomised study (NCT00506350; an extension of an earlier randomised study) we assessed immunogenicity in nine groups of 35-50 volunteers aged 19-61 years following administration of AS03(A)-adjuvanted split-virion H5N1 vaccine containing 3.75mug of haemagglutinin (HA) from the A/Indonesia/5/2005(IBCDC-RG2) clade 2.1 strain. A single booster dose of vaccine was administered to four groups primed 14 months previously with different HA levels of AS03(A)-adjuvanted clade 1 A/Vietnam/1194/2004 H5N1 vaccine. Two booster doses (given 21 days apart) were administered to four groups primed 14 months previously with different HA levels of non-adjuvanted A/Vietnam/1194/2004 H5N1 vaccine and also to a control group of un-primed subjects. In individuals primed 14 months earlier with AS03(A)-adjuvanted A/Vietnam/1194/2004 vaccines, a single booster dose of AS03(A)-adjuvanted A/Indonesia/5/2005 induced rapid immune responses (licensure criteria met in 7-14 days) comparable to that observed in the un-primed control group following two doses of adjuvanted vaccine. In contrast, individuals primed with non-adjuvanted formulations exhibited minimal immune responses which, even after two doses, were unexpectedly much lower than that observed in un-primed subjects. AS03(A) enhances the initial priming effect of pandemic influenza vaccination enabling a rapid humoral response to single dose boosting with a heterologous strain at 14 months. In contrast, priming without adjuvant appears to inhibit the response to subsequent vaccination with a heterologous strain. These findings should guide the development of vaccines to combat the present influenza A/H1N1 pandemic.

A vaccine manufacturer's approach to address medical needs related to seasonal and pandemic influenza viruses.

Vaccination is considered to be one of the most effective tools to decrease morbidity as well as mortality caused by influenza viruses. For the prevention of seasonal influenza, Fluarix and FluLaval have been marketed since 1987 and 1992, respectively. Both vaccines have consistently been shown to meet or exceed the regulatory criteria for immunogenicity against the three strains H1N1, H3N2 and B, have a good safety profile, and are recommended for vaccinating children and adults of all ages. For the prevention of pandemic influenza, GlaxoSmithKline (GSK) has obtained licensure of a pre-pandemic vaccine, Prepandrix. This split-virus H5N1 adjuvanted with AS03, a proprietary oil-in-water emulsion-based adjuvant system, has demonstrated broad immunity against drifted H5N1 strains and has been shown to be effective in preventing mortality and viral shedding in animal studies. The influenza vaccine portfolio of GSK addresses specific medical needs related to seasonal or pandemic influenza viruses, which remain an important public health threat worldwide.

Broad Clade 2 cross-reactive immunity induced by an adjuvanted clade 1 rH5N1 pandemic influenza vaccine.

BACKGROUND: The availability of H5N1 vaccines that can elicit a broad cross-protective immunity against different currently circulating clade 2 H5N1 viruses is a pre-requisite for the development of a successful pre-pandemic vaccination strategy. In this regard, it has recently been shown that adjuvantation of a recombinant clade 1 H5N1 inactivated split-virion vaccine with an oil-in-water emulsion-based adjuvant system also promoted cross-immunity against a recent clade 2 H5N1 isolate (A/Indonesia/5/2005, subclade 2.1). Here we further analyse the cross-protective potential of the vaccine against two other recent clade 2 isolates (A/turkey/Turkey/1/2005 and A/Anhui/1/2005 which are, as defined by WHO, representatives of subclades 2.2 and 2.3 respectively). METHODS AND FINDINGS: Two doses of the recombinant A/Vietnam/1194/2004 (H5N1, clade 1) vaccine were administered 21 days apart to volunteers aged 18-60 years. We studied the cross-clade immunogenicity of the lowest antigen dose (3.8 microg haemagglutinin) given with (N = 20) or without adjuvant (N = 20). Immune responses were assessed at 21 days following the first and second vaccine doses and at 6 months following first vaccination. Vaccination with two doses of 3.8 microg of the adjuvanted vaccine induced four-fold neutralising seroconversion rates in 85% of subjects against A/turkey/Turkey/1/2005 (subclade 2.2) and 75% of subjects against A/Anhui/1/2005 (subclade 2.3) recombinant strains. There was no response induced against these strains in the non-adjuvanted group. At 6 months following vaccination, 70% and 60% of subjects retained neutralising antibodies against the recombinant subclade 2.2 and 2.3 strains, respectively and 40% of subjects retained antibodies against the recombinant subclade 2.1 A/Indonesia/5/2005 strain. CONCLUSIONS: In addition to antigen dose-sparing, adjuvantation of inactivated split H5N1 vaccine promotes broad and persistent cross-clade immunity which is a pre-requisite for a pre-pandemic vaccine. TRIAL REGISTRATION: ClinicalTrials.gov NCT00309634.

Vaccine adjuvant systems containing monophosphoryl lipid A and QS21 induce strong and persistent humoral and T cell responses against hepatitis B surface antigen in healthy adult volunteers.

A randomised, double-blind study assessing the potential of four adjuvants in combination with recombinant hepatitis B surface antigen has been conducted to evaluate humoral and cell-mediated immune responses in healthy adults after three vaccine doses at months 0, 1 and 10. Three Adjuvant Systems (AS) contained 3-O-desacyl-4'-monophosphoryl lipid A (MPL) and QS21, formulated either with an oil-in-water emulsion (AS02B and AS02V) or with liposomes (AS01B). The fourth adjuvant was CpG oligonucleotide. High levels of antibodies were induced by all adjuvants, whereas cell-mediated immune responses, including cytolytic T cells and strong and persistent CD4(+) T cell response were mainly observed with the three MPL/QS21-containing Adjuvant Systems. The CD4(+) T cell response was characterised in vitro by vigorous lymphoproliferation, high IFN-gamma and moderate IL-5 production. Antigen-specific T cell immune response was further confirmed ex vivo by detection of IL-2- and IFN-gamma-producing CD4(+) T cells, and in vivo by measuring increased levels of IFN-gamma in the serum and delayed-type hypersensitivity (DTH) responses. The CpG adjuvanted vaccine induced consistently lower immune responses for all parameters. All vaccine adjuvants were shown to be safe with acceptable reactogenicity profiles. The majority of subjects reported local reactions at the injection site after vaccination while general reactions were recorded less frequently. No vaccine-related serious adverse event was reported. Importantly, no increase in markers of auto-immunity and allergy was detected over the whole study course. In conclusion, the Adjuvant Systems containing MPL/QS21, in combination with hepatitis B surface antigen, induced very strong humoral and cellular immune responses in healthy adults. The AS01B-adjuvanted vaccine induced the strongest and most durable specific cellular immune responses after two doses. These Adjuvant Systems, when added to recombinant protein antigens, can be fundamental to develop effective prophylactic vaccines against complex pathogens, e.g. malaria, HIV infection and tuberculosis, and for special target populations such as subjects with an impaired immune response, due to age or medical conditions.

Cross-protection against lethal H5N1 challenge in ferrets with an adjuvanted pandemic influenza vaccine.

BACKGROUND: Unprecedented spread between birds and mammals of highly pathogenic avian influenza viruses (HPAI) of the H5N1 subtype has resulted in hundreds of human infections with a high fatality rate. This has highlighted the urgent need for the development of H5N1 vaccines that can be produced rapidly and in sufficient quantities. Potential pandemic inactivated vaccines will ideally induce substantial intra-subtypic cross-protection in humans to warrant the option of use, either prior to or just after the start of a pandemic outbreak. In the present study, we evaluated a split H5N1 A/H5N1/Vietnam/1194/04, clade 1 candidate vaccine, adjuvanted with a proprietary oil-in- water emulsion based Adjuvant System proven to be well-tolerated and highly immunogenic in the human (Leroux-Roels et al. (2007) The Lancet 370:580-589), for its ability to induce intra-subtypic cross-protection against clade 2 H5N1/A/Indonesia/5/05 challenge in ferrets. METHODOLOGY AND PRINCIPAL FINDINGS: All ferrets in control groups receiving non-adjuvanted vaccine or adjuvant alone failed to develop specific or cross-reactive neutralizing antibodies and all died or had to be euthanized within four days of virus challenge. Two doses of adjuvanted split H5N1 vaccine containing >or=1.7 microg HA induced neutralizing antibodies in the majority of ferrets to both clade 1 (17/23 (74%) responders) and clade 2 viruses (14/23 (61%) responders), and 96% (22/23) of vaccinees survived the lethal challenge. Furthermore lung virus loads and viral shedding in the upper respiratory tract were reduced in vaccinated animals relative to controls suggesting that vaccination might also confer a reduced risk of viral transmission. CONCLUSION: These protection data in a stringent challenge model in association with an excellent clinical profile highlight the potential of this adjuvanted H5N1 candidate vaccine as an effective tool in pandemic preparedness.