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The Possible Impact of Vaccination for Seasonal Influenza on Emergence of Pandemic Influenza via Reassortment.

Abstract

BACKGROUND

One pathway through which pandemic influenza strains might emerge is reassortment from coinfection of different influenza A viruses. Seasonal influenza vaccines are designed to target the circulating strains, which intuitively decreases the prevalence of coinfection and the chance of pandemic emergence due to reassortment. However, individual-based analyses on 2009 pandemic influenza show that the previous seasonal vaccination may increase the risk of pandemic A(H1N1) pdm09 infection. In view of pandemic influenza preparedness, it is essential to understand the overall effect of seasonal vaccination on pandemic emergence via reassortment.

METHODS AND FINDINGS

In a previous study we applied a population dynamics approach to investigate the effect of infection-induced cross-immunity on reducing such a pandemic risk. Here the model was extended by incorporating vaccination for seasonal influenza to assess its potential role on the pandemic emergence via reassortment and its effect in protecting humans if a pandemic does emerge. The vaccination is assumed to protect against the target strains but only partially against other strains. We find that a universal seasonal vaccine that provides full-spectrum cross-immunity substantially reduces the opportunity of pandemic emergence. However, our results show that such effectiveness depends on the strength of infection-induced cross-immunity against any novel reassortant strain. If it is weak, the vaccine that induces cross-immunity strongly against non-target resident strains but weakly against novel reassortant strains, can further depress the pandemic emergence; if it is very strong, the same kind of vaccine increases the probability of pandemic emergence.

CONCLUSIONS

Two types of vaccines are available: inactivated and live attenuated, only live attenuated vaccines can induce heterosubtypic immunity. Current vaccines are effective in controlling circulating strains; they cannot always help restrain pandemic emergence because of the uncertainty of the oncoming reassortant strains, however. This urges the development of universal vaccines for prevention of pandemic influenza.

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  • Authors+Show Affiliations

    ,

    Modelling and Economics Unit, Centre for Infectious Disease Surveillance and Control, Public Health England, London, United Kingdom; Medical Research Council Centre for Outbreak Analysis and Modelling, Department of Infectious Disease Epidemiology, Imperial College School of Public Health, London, United Kingdom.

    ,

    Respiratory Diseases Department, Centre for Infectious Disease Surveillance and Control, Public Health England, London, United Kingdom.

    ,

    Statistics Unit, Centre for Infectious Disease Surveillance and Control, Public Health England, London, United Kingdom; Medical Research Council Biostatistics Unit, University Forvie Site, Cambridge, United Kingdom.

    ,

    Modelling and Economics Unit, Centre for Infectious Disease Surveillance and Control, Public Health England, London, United Kingdom; Medical Research Council Centre for Outbreak Analysis and Modelling, Department of Infectious Disease Epidemiology, Imperial College School of Public Health, London, United Kingdom; NIHR Health Protection Research Unit in Modelling Methodology, Department of Infectious Disease Epidemiology, Imperial College School of Public Health, London, United Kingdom.

    ,

    Statistics Unit, Centre for Infectious Disease Surveillance and Control, Public Health England, London, United Kingdom.

    Medical Research Council National Institute for Medical Research, Mill Hill, London, United Kingdom.

    Source

    PloS one 9:12 2014 pg e114637

    Pub Type(s)

    Journal Article

    Language

    eng

    PubMed ID

    25494180

    Citation

    TY - JOUR T1 - The Possible Impact of Vaccination for Seasonal Influenza on Emergence of Pandemic Influenza via Reassortment. AU - Zhang,Xu-Sheng, AU - Pebody,Richard, AU - De Angelis,Daniela, AU - White,Peter J, AU - Charlett,Andre, AU - McCauley,John W, Y1 - 2014/12/10/ PY - 2014/05/06/received PY - 2014/11/12/accepted PY - 2014/12/11/entrez PY - 2014/12/11/pubmed PY - 2014/12/11/medline SP - e114637 EP - e114637 JF - PloS one JO - PLoS ONE VL - 9 IS - 12 N2 - BACKGROUND: One pathway through which pandemic influenza strains might emerge is reassortment from coinfection of different influenza A viruses. Seasonal influenza vaccines are designed to target the circulating strains, which intuitively decreases the prevalence of coinfection and the chance of pandemic emergence due to reassortment. However, individual-based analyses on 2009 pandemic influenza show that the previous seasonal vaccination may increase the risk of pandemic A(H1N1) pdm09 infection. In view of pandemic influenza preparedness, it is essential to understand the overall effect of seasonal vaccination on pandemic emergence via reassortment. METHODS AND FINDINGS: In a previous study we applied a population dynamics approach to investigate the effect of infection-induced cross-immunity on reducing such a pandemic risk. Here the model was extended by incorporating vaccination for seasonal influenza to assess its potential role on the pandemic emergence via reassortment and its effect in protecting humans if a pandemic does emerge. The vaccination is assumed to protect against the target strains but only partially against other strains. We find that a universal seasonal vaccine that provides full-spectrum cross-immunity substantially reduces the opportunity of pandemic emergence. However, our results show that such effectiveness depends on the strength of infection-induced cross-immunity against any novel reassortant strain. If it is weak, the vaccine that induces cross-immunity strongly against non-target resident strains but weakly against novel reassortant strains, can further depress the pandemic emergence; if it is very strong, the same kind of vaccine increases the probability of pandemic emergence. CONCLUSIONS: Two types of vaccines are available: inactivated and live attenuated, only live attenuated vaccines can induce heterosubtypic immunity. Current vaccines are effective in controlling circulating strains; they cannot always help restrain pandemic emergence because of the uncertainty of the oncoming reassortant strains, however. This urges the development of universal vaccines for prevention of pandemic influenza. SN - 1932-6203 UR - https://www.unboundmedicine.com/medline/citation/25494180/The_Possible_Impact_of_Vaccination_for_Seasonal_Influenza_on_Emergence_of_Pandemic_Influenza_via_Reassortment_ L2 - http://dx.plos.org/10.1371/journal.pone.0114637 ER -