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From Future Microbiology
The Ins and Outs of Universal Childhood Influenza Vaccination
Pieter LA Fraaij; Rogier Bodewes; Albert DME Osterhaus; Guus F Rimmelzwaan
Authors and Disclosures
Posted: 11/08/2011; Future Microbiology. 2011;6(10):1171-1184. © 2011 Future Medicine Ltd.
Influenza viruses continue to cause disease of varying severity among humans. People with underlying disease and the elderly are at increased risk of developing severe disease after infection with an influenza virus. As effective and safe vaccines are available, the WHO has recommended vaccinating these groups against influenza annually. In addition to this recommendation, public health authorities of a number of countries have recently recommended vaccinating all healthy children aged 6–59 months against influenza. Here, we review the currently available data concerning the burden of disease in children, the economical impact of implementing universal vaccination of children, the efficacy of currently available influenza virus vaccines, the theoretical concerns regarding preventing immunity otherwise induced by infections with seasonal influenza viruses, and finally, how to address these concerns.
Influenza viruses are an important cause of respiratory tract infections in humans and cause disease of varying severity and even death. In addition to the annually recurring seasonal influenza outbreaks in moderate climate zones, pandemic outbreaks of influenza occur (worldwide outbreaks of influenza in humans), caused by novel influenza A viruses antigenically distinct from the seasonal influenza viruses. The most infamous example of such a pandemic is the 'Spanish flu', which emerged in 1918 and caused more than 50 million fatal cases worldwide.[1,2] Infections with the 2009 pandemic influenza A/H1N1 viruses displayed a broad spectrum of disease severity ranging from mild to severe disease and death.[3–5] This unpredictability of disease severity is also a hallmark of seasonal influenza outbreaks. Typically, seasonal or interpandemic clinical influenza activity can range from almost absent to more than ten reported influenza cases per 10,000 individuals per week. In addition, during outbreaks, marked differences in the incidence of the disease can be observed between geographical regions.[6] This variability in disease burden depends, in part, on the virus' ability to escape the host's immunosurveillance.[7–9] In this article we focus on vaccination as a measure to protect from seasonal influenza virus infections. Vaccination against pandemic influenza will only be discussed briefly. As a result of selective pressure by virus-neutralizing antibodies, seasonal influenza viruses continue to accumulate amino acid substitutions predominantly in antigenic sites located in the hemagglutinin. As a result, the vaccine needs to be updated regularly and it is recommended to vaccinate annually before the influenza season to protect against the most recent strains of influenza viruses that have emerged. When implemented, annual vaccination against influenza is a powerful tool to reduce morbidity and mortality caused by influenza virus infections.[201] Currently, different types of influenza vaccines are available, including live-attenuated and inactivated (subunit) vaccines. During the pandemic in 2009, adjuvanted subunit vaccines were widely used.[10] For the discussion on the need to vaccinate selected target populations it is pivotal to establish the burden of disease in these patient groups. In this respect the excess morbidity and mortality caused by influenza virus infections during seasonal outbreaks have clearly been shown for individuals aged 60 years and older.[11–13] In addition, the same holds true for individuals, including children, affected by certain medical conditions including cardiopulmonary disease, metabolic disorders, neurological disease and the (iatrogenic) immune compromised.[201] The WHO advises on the vaccination of individuals with one of the aforementioned mentioned risk factors.[10] However, for healthy children these data on the burden of disease are less evident and sometimes even conflicting. In this article we discuss the in and outs of universal childhood influenza vaccination. This will be done in the light of the available relevant literature on the influenza-related disease burden, side effects and efficacy of influenza vaccination in the global pediatric population. In addition, theoretical concerns that were raised recently regarding the prevention of heterosubtypic immunity by annual vaccination of children against seasonal influenza will be discussed.
The Ins and Outs of Universal Childhood Influenza Vaccination
Pieter LA Fraaij; Rogier Bodewes; Albert DME Osterhaus; Guus F Rimmelzwaan
Authors and Disclosures
Posted: 11/08/2011; Future Microbiology. 2011;6(10):1171-1184. © 2011 Future Medicine Ltd.
Influenza viruses continue to cause disease of varying severity among humans. People with underlying disease and the elderly are at increased risk of developing severe disease after infection with an influenza virus. As effective and safe vaccines are available, the WHO has recommended vaccinating these groups against influenza annually. In addition to this recommendation, public health authorities of a number of countries have recently recommended vaccinating all healthy children aged 6–59 months against influenza. Here, we review the currently available data concerning the burden of disease in children, the economical impact of implementing universal vaccination of children, the efficacy of currently available influenza virus vaccines, the theoretical concerns regarding preventing immunity otherwise induced by infections with seasonal influenza viruses, and finally, how to address these concerns.
Influenza viruses are an important cause of respiratory tract infections in humans and cause disease of varying severity and even death. In addition to the annually recurring seasonal influenza outbreaks in moderate climate zones, pandemic outbreaks of influenza occur (worldwide outbreaks of influenza in humans), caused by novel influenza A viruses antigenically distinct from the seasonal influenza viruses. The most infamous example of such a pandemic is the 'Spanish flu', which emerged in 1918 and caused more than 50 million fatal cases worldwide.[1,2] Infections with the 2009 pandemic influenza A/H1N1 viruses displayed a broad spectrum of disease severity ranging from mild to severe disease and death.[3–5] This unpredictability of disease severity is also a hallmark of seasonal influenza outbreaks. Typically, seasonal or interpandemic clinical influenza activity can range from almost absent to more than ten reported influenza cases per 10,000 individuals per week. In addition, during outbreaks, marked differences in the incidence of the disease can be observed between geographical regions.[6] This variability in disease burden depends, in part, on the virus' ability to escape the host's immunosurveillance.[7–9] In this article we focus on vaccination as a measure to protect from seasonal influenza virus infections. Vaccination against pandemic influenza will only be discussed briefly. As a result of selective pressure by virus-neutralizing antibodies, seasonal influenza viruses continue to accumulate amino acid substitutions predominantly in antigenic sites located in the hemagglutinin. As a result, the vaccine needs to be updated regularly and it is recommended to vaccinate annually before the influenza season to protect against the most recent strains of influenza viruses that have emerged. When implemented, annual vaccination against influenza is a powerful tool to reduce morbidity and mortality caused by influenza virus infections.[201] Currently, different types of influenza vaccines are available, including live-attenuated and inactivated (subunit) vaccines. During the pandemic in 2009, adjuvanted subunit vaccines were widely used.[10] For the discussion on the need to vaccinate selected target populations it is pivotal to establish the burden of disease in these patient groups. In this respect the excess morbidity and mortality caused by influenza virus infections during seasonal outbreaks have clearly been shown for individuals aged 60 years and older.[11–13] In addition, the same holds true for individuals, including children, affected by certain medical conditions including cardiopulmonary disease, metabolic disorders, neurological disease and the (iatrogenic) immune compromised.[201] The WHO advises on the vaccination of individuals with one of the aforementioned mentioned risk factors.[10] However, for healthy children these data on the burden of disease are less evident and sometimes even conflicting. In this article we discuss the in and outs of universal childhood influenza vaccination. This will be done in the light of the available relevant literature on the influenza-related disease burden, side effects and efficacy of influenza vaccination in the global pediatric population. In addition, theoretical concerns that were raised recently regarding the prevention of heterosubtypic immunity by annual vaccination of children against seasonal influenza will be discussed.
