Inactivated Influenza Vaccine Effectiveness in Tropical Africa
Condition: Influenza
MeSH terms: Influenza, Human
Study type: Interventional
Phase: Phase 4

Summary: 
      Influenza, a highly communicable acute respiratory disease, is one of the major infectious
      disease threats to the human population. In Africa, information on the occurrence of
      influenza and its disease burden is seriously lacking. Such data would be important in
      determining the contribution of influenza to the more than two million annual pneumonia
      deaths among children globally, mostly in the developing world, and the potential number of
      deaths that could be prevented by influenza vaccination.

      A single dose of trivalent inactivated influenza vaccine (TIV) is 70 to 90 percent effective
      in preventing influenza in healthy older children and young and middle-aged adults, but is
      less efficacious in young children and the elderly. Young children who suffer substantial
      influenza morbidity and are unlikely to have pre-existing immunity should receive two doses
      of TIV to provide adequate immunity. Because family studies of influenza transmission
      conducted during the 1970's found children to be the main introducers of influenza into
      households, vaccination of children may decrease the chances of spreading influenza to
      contacts. Mass vaccination of schoolchildren has been correlated with reduced respiratory
      illness in unvaccinated persons suggesting that immunization of children on a larger scale
      can affect community epidemics.

      In temperate industrialized countries with seasonal disease, influenza vaccine is given
      annually, prior to the influenza season, and generally targeted to individuals with the
      highest risk of severe disease. Influenza prevention strategies may need to differ in
      tropical developing countries due to a variety of reasons. Given the varying influenza
      circulation patterns, it is unknown which hemisphere vaccine formulation will provide
      year-round protection against the diverse strains that may exist in tropical countries.
      Persons residing in developing countries also may have nutritional deficiencies or underlying
      diseases and infections that affect vaccine immunogenicity. Consideration must be given to
      programmatic issues as well. Adolescent and adult preventive health services are poorly
      developed in many countries, and thus a strategy that targets children may be the most
      feasible option. In addition, vaccinating children may be the most cost-effective option, as
      it has the potential to provide direct benefit to those vaccinated, as well as indirect
      benefits to unvaccinated members of the population. Thus, an influenza vaccine effectiveness
      study in a tropical developing country population will help to elucidate burden of seasonal
      influenza and may inform optimal use of vaccine for either seasonal and pandemic situations.

      Thus, this study in Senegal will to evaluate the direct effects of TIV in reducing the
      occurrence of laboratory-confirmed influenza among children who receive it as well as the
      potential indirect effects experienced by the population as a result of reducing transmission
      among children.
    

Detailed description: 
      The trial will take place in the study area of the Niakhar demographic surveillance system in
      Senegal, a population representative of rural impoverished Africa. Villages will be
      randomized to TIV or a beneficial control vaccine-inactivated polio vaccine-and children 6
      months to 10 years of age will be targeted for vaccination. Four hundred children will be
      further enrolled into an immunogenicity and safety substudy which will measure their immune
      response to vaccination and assess in detail reactions and adverse events to the vaccines in
      these populations. For evaluation of effectiveness, passive and active surveillance will be
      conducted to identify laboratory-confirmed influenza among enrolled children and in the
      population in which they live. Such surveillance will also allow a determination of the rates
      of influenza and a description of the clinical characteristics of the disease in an African
      population. With such epidemiologic data, national and global public health officials will
      have better data for developing future influenza control strategies for either seasonal or
      pandemic influenza.
    

Intervention name(s): seasonal trivalent inactivated influenza vaccine; inactivated polio vaccine
Intervention type(s): Biological; Biological
Intervention description(s): vaccine to be used according to marketed dosage and frequency; vaccine to be used according to marketed dosage and frequency
Other intervention name(s): Vaxigrip; Imovax Polio
Intervention MeSH terms: Vaccines
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Double (Participant, Outcomes Assessor)
Primary purpose: Prevention
Keywords: influenza; influenza vaccine; vaccine effectiveness; cluster randomized; Africa