Increased substitution rate in H5N1 avian influenza viruses during mass vaccination of poultry

Benefit-cost analysis of a H7N9 vaccination program in poultry in Guangxi, China

China launched a H7N9 vaccination program in poultry, starting from the Guangxi and Guangdong provinces in July 2017, followed by other provinces in September 2017, as a response to a steep increase of H7N9 influenza human infections from September 2016. Since then, H5-H7 bivalent vaccine has been used in the nationwide avian influenza compulsory vaccination program to replace the existing H5N1 vaccine. However, the economic returns of the H7N9 vaccination program in China have never been adequately assessed. This study was designed to evaluate the economic value of the H7N9 vaccination program in Guangxi by assessing the benefits and costs of the program compared to not vaccinating against H7N9. A benefit-cost analysis (BCA) was undertaken to evaluate the adoption of a vaccination program against H7N9 in each of three consecutive years from July 2017 to June 2020 with the baseline scenario (the absence of H7N9 vaccination in the 12-month period July 2016 to June 2017). Both animal and public health perspectives were included in the BCA framework and took account of both the private and public sectors. Benefit-Cost Ratio (BCR) of the three-year H7N9 vaccination program was 18.6 (90 %PI: 15.4; 21.8), and total Net Present Values reached to CNY 1.63 billion (90 %PI: 1.37 billion; 1.89 billion). The extra revenue generated by the yellow broiler industry comprised 93.8 % of the total benefits after adoption of H7N9 vaccination program in Guangxi. While cost-savings in public health and animal health expenditure avoided were 3.6 % and 2.6 %, respectively. Total costs arising from adoption of the revised vaccination program over the three years were CNY 12.46 million (90 %PI: 11.49 million; 14.14 million), CNY 34.87 million (90 %PI: 31.88 million; 40.06 million), and CNY 44.28 million (90 %PI: 39.66 million; 52.27 million), respectively. Sensitivity analysis found the yellow broiler wholesale prices contributed 97.7 % of the variance of the total NPV of three vaccination years. The study results demonstrate the significant economic advantage of implementing a vaccination program against H7N9 in Guangxi. It also offers a new set of evidence to China's H7N9 vaccination policy and debates around economic values of conducting routine avian influenza vaccination.

A mixed methods study of stakeholders' practices and attitudes on avian influenza H7N9 vaccination for the yellow broiler industry in Guangxi, China

In response to a sudden increase in H7N9 human infections, China introduced an H5/H7 bivalent inactivated vaccine for poultry in Guangxi and Guangdong provinces in July 2017, which subsequently became integrated into the existing compulsory national H5N1 vaccination programme from September 2017. Although the vaccination programme effectively reduced H7N9 infections in humans and poultry, there are ongoing arguments against continuing this long-term vaccination. These discussions have drawn policymakers to think about the possibility of stopping routine vaccination for H7N9 avian influenza viruses (AIVs) in China; however, they have not considered the poultry industry stakeholders' practices on and attitudes towards this vaccination. This study investigated H7N9 vaccination practices in the yellow broiler industry in Guangxi and stakeholders' attitudes on H7N9 vaccination, using a mixed methods design. The study found H7N9 vaccination was well adopted in the yellow broiler industry in Guangxi regardless of the source of the vaccines. Most stakeholders believed vaccination was the best measure to control H7N9 and H5N1 AIVs, and they showed a strong willingness to continue with vaccination even without government subsidies or freely provided vaccines. The motivations by stakeholders for using vaccines to control H7N9 and H5N1 were different due to the epidemiological differences between the two strains. Understanding poultry industry stakeholders' practices and attitudes on H7N9 vaccination has important practical implications in planning vaccination policies, particularly when considering the possibility of vaccination withdrawal.

Potential of live pathogen vaccines for defeating the COVID-19 pandemic: History and mechanism

The whole world has entered a terrible crisis with a huge and increasing number of human deaths and economic losses in fighting the pandemic of COVID‐19 caused by the novel coronavirus termed SARS‐CoV‐2. The live pathogen vaccine (LPV) strategy, which originated in ancient China for fighting smallpox, has been applied successfully by US military recruits for decades to control acute respiratory diseases caused by types 4 and 7 adenoviruses. This strategy has also been widely employed in veterinary medicine. These facts suggest a fast way out of the current pandemic crisis, namely that SARS‐CoV‐2 could be directly used as a live vaccine. Beyond the two traditional mechanisms to guarantee the LPV's safety (the LPV seed strain is properly selected; the LPV is inoculated bypassing the respiratory sites of pathology), three novel mechanisms to further ensure the LPV's safety are available (the virus replication is inhibited with early use of an antiviral drug; symptomatic LPV recipients are cured with convalescent plasma; the LPV is inoculated in the hot season). This LPV strategy has multiple potential advantages over other options and could reduce morbidity and mortality greatly as well as the economic loss caused by the pandemic. The safety and efficacy of this strategy should be investigated strictly using animal experiments and clinical trials, and even if the experiments and trials all support the strategy, it should be implemented with enough caution.

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The world has entered a terrible crisis in fighting the COVID‐19 pandemic.

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Live pathogen vaccines (LPV) have defeated infectious diseases caused by adenoviruses.

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The LPV strategy has been widely employed in veterinary medicine.

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The LPV strategy could be a way out of the COVID‐19 pandemic crisis.

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Five mechanisms can be employed to ensure the safety of the LPV of SARS‐CoV‐2.

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The LPV strategy should be examined with animal experiments and clinical trials.

Genetic evolution and transmission dynamics of clade 2.3.2.1a highly pathogenic avian influenza A/H5N1 viruses in Bangladesh

Asian lineage A/H5N1 highly pathogenic avian influenza viruses (HPAIVs) have been responsible for continuous outbreaks in Bangladesh since 2007. Although clades 2.2.2 and 2.3.4.2 HPAIVs have disappeared since poultry vaccination was introduced in 2012, clade 2.3.2.1a viruses have continued to be detected in Bangladesh. In this study, we identified A/H9N2 (n = 15), A/H5N1 (n = 19), and A/H5N1-A/H9N2 (n = 18) mixed viruses from live bird markets, chicken farms, and wild house crows (Corvus splendens) in Bangladesh from 2016 to 2018. We analyzed the genetic sequences of the H5 HPAIVs, to better understand the evolutionary history of clade 2.3.2.1a viruses in Bangladesh. Although seven HA genetic subgroups (B1-B7) and six genotypes (G1, G1.1, G1.2, G2, G2.1, and G2.2) have been identified in Bangladesh, only subgroup B7 and genotypes G2, G2.1, and G2.2 were detected after 2016. The replacement of G1 genotype by G2 in Bangladesh was possibly due to vaccination and viral competition in duck populations. Initially, genetic diversity decreased after introduction of vaccination in 2012, but in 2015, genetic diversity increased and was associated with the emergence of genotype G2. Our phylodynamic analysis suggests that domestic Anseriformes, including ducks and geese, may have played a major role in persistence, spread, evolution, and genotype replacement of clade 2.3.2.1a HPAIVs in Bangladesh. Thus, improvements in biosecurity and monitoring of domestic Anseriformes are needed for more effective control of HPAI in Bangladesh.

Control of avian influenza in China: Strategies and lessons

In recent decades, multiple subtypes (i.e. H9N2, H5N1 and H7N9) of avian influenza virus (AIV) have become widespread in China, which has caused enormous economic losses and posed considerable threats to public health. In this review, with the aim to provide insights into and guidelines for the control of AIV spread in China and globally in the future, we analysed the reasons why AIV has persisted in China based on socio-economic features, including poultry biosecurity, live bird markets, live bird transportation, wild birds, poultry waterfowl, poultry density, poultry population and infected birds. We also described the present status of the AIV subtypes H9, H5 and H7 in China to elucidate the effectiveness of the strategies currently employed in China (i.e. culling, mass vaccination and biosecurity improvement) to control the disease based on a literature review and our unpublished surveillance data collected over a 12-year period from 2007 to 2018. We then summarized the lessons to be learned from the control experience in China, including whether culling of infected birds is of limited value for disease control and whether improved biosecurity is a better option than culling and vaccination for the long-term control of AIV, and when the vaccine strain should be updated.

Assessment of China's H5N1 routine vaccination strategy

In this study, a simulation model was used to assess the epidemiological and economic impacts of the routine vaccination strategy for H5N1 in China at the national level. The results of the simulation show that a routine vaccination strategy at the national level could have a substantial impact on decreasing H5N1 outbreaks; it could therefore markedly reduce the severity and duration of an H5N1 epidemic at the national level in China. Under a routine vaccination programme, when a flock is infected, the number of depopulated birds could be reduced by approximately 91%, the outbreak duration could be reduced by one-fourth, and the probability of an H5N1 outbreak could be reduced to 51.5%. Although the use of vaccination has obvious benefits, if indirect costs were not considered, the mean direct cost of simulated disease control without vaccination was only 1.36% of the cost of the routine vaccination strategy, and this former approach would have saved 57 billion yuan for all poultry in China from 2004 to 2012. Traditional H5N1 control strategies with culling programmes at the national level represented a better choice for China.

Visualization of Alternative Functional Configurations of Influenza Virus Hemagglutinin Facilitates Rapid Selection of Complementing Vaccines in Emergency Situations

Successful immunization against avian influenza virus (AIV) requires eliciting an adequate polyclonal response to AIV hemagglutinin (HA) subunit 1 (HA1) epitopes. Outbreaks of highly-pathogenic (HP) AIV subtype H5N1 can occur in vaccinated flocks in many endemic areas. Protection against emerging AIV is partly hindered by the limitations of vaccine production and transport, the use of leaky vaccines, and the use of multiple, and often antigenically-diverse, vaccines. It was hypothesized that the majority of alternative functional configurations (AFC) within the AIV HA1 can be represented by the pool of vaccine seed viruses currently in production because only a finite number of AFC are possible within each substructure of the molecule. Therefore, combinations of commercial vaccines containing complementing structural units (CSU) to each HA1 substructure can elicit responses to the totality of a given emerging AIV HA1 substructure isoforms. Analysis of homology-based 3D models of vaccine seed and emerging viruses facilitated the definition of HA1 AFC isoforms. CSU-based plots were used to predict which commercial vaccine combinations could have been used to cover nine selected AFC isoforms on recent Egyptian HP AIV H5N1 outbreak viruses. It is projected that expansion of the vaccine HA1 3D model database will improve international emergency responses to AIV.

Natural history of highly pathogenic avian influenza H5N1

The ecology of highly pathogenic avian influenza (HPAI) H5N1 has significantly changed from sporadic outbreaks in terrestrial poultry to persistent circulation in terrestrial and aquatic poultry and potentially in wild waterfowl. A novel genotype of HPAI H5N1 arose in 1996 in Southern China and through ongoing mutation, reassortment, and natural selection, has diverged into distinct lineages and expanded into multiple reservoir hosts. The evolution of Goose/Guangdong-lineage highly pathogenic H5N1 viruses is ongoing: while stable interactions exist with some reservoir hosts, these viruses are continuing to evolve and adapt to others, and pose an un-calculable risk to sporadic hosts, including humans.