Inactivated Influenza Vaccine Effectiveness in Tropical Africa

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.

Timeline

Start

2009-05

Primary completion

2012-12

Completion

2013-04

Publications

• Niang MN, Sugimoto JD, Diallo A, Diarra B, Ortiz JR, Lewis KDC, Lafond KE, Halloran ME, Widdowson MA, Neuzil KM, Victor JC. Estimates of Inactivated Influenza Vaccine Effectiveness Among Children in Senegal: Results From 2 Consecutive Cluster-Randomized Controlled Trials in 2010 and 2011. Clin Infect Dis. 2021 Jun 15;72(12):e959-e969. doi: 10.1093/cid/ciaa1689.
• Diallo A, Diop OM, Diop D, Niang MN, Sugimoto JD, Ortiz JR, Faye EHA, Diarra B, Goudiaby D, Lewis KDC, Emery SL, Zangeneh SZ, Lafond KE, Sokhna C, Halloran ME, Widdowson MA, Neuzil KM, Victor JC. Effectiveness of Seasonal Influenza Vaccination in Children in Senegal During a Year of Vaccine Mismatch: A Cluster-randomized Trial. Clin Infect Dis. 2019 Oct 30;69(10):1780-1788. doi: 10.1093/cid/ciz066.

Drugs

Indications