Beating the flu: could children be the answer?

The influenza emergency in the United States is not over and its bill is running on. After less than one week from the announcement of the Food and Drug Administration (FDA) approval of Flublok, the first trivalent seasonal influenza vaccine produced with help of recombinant DNA technology, new data (1) arrived from Centers of Disease Control and Prevention (CDC) about the impact of seasonal influenza vaccines on U.S. population. The estimated vaccine effectiveness (VE) was 62% (95% confidence intervals [CIs] = 51%–71%), a moderate effectiveness. Mitigating the outbreak still represents the imperative to follow for trying to limit the damage to economy and health. The vaccine should be administered to all people aged > 6 months, including the healthy children. This choice goes along with a series of economic and medical reasons (2). Children are the major source for the spreading and the vaccination not only reduces the effects and complications in vaccinated children, but could also contain the diffusion to unvaccinated subjects, their relatives and household members (herd immunity). Evaluating the safety and the effectiveness in this category of population is essential (3,4) to routinely consider their inclusion in a worldwide vaccination programme against the influenza. Currently just two options are available for children vaccination. A recent meta-analysis published on The Lancet Infectious Diseases shows how the Trivalent inactivated vaccines (TIV),currently the only preparations indicated for children over 6 months, present a variable protection depending on the seasons (5), while the Live-attenuated influenza vaccines (LAIV) turn out to have a greater efficacy in children compared to adults. However, just one study is available about the efficacy of TIV in children aged 6-24 months in two different seasons (1999-2000 and 2000-2001) with an efficacy range from 66% to -7% (95% CI)(6).

At the present moment in the UK and other European countries, influenza vaccination is only provided for babies over 6 months with long-term health conditions. According to World Health Organization (7), although the major childhood mortality occurs in developing countries, children under 2 years present a high burden of influenza with possible severe respiratory and hemodynamic consequences and high rates of hospitalization. Moreover, children who attend day care centres and schools represent a dangerous carrier for the community.

Are the children an overlooked target for our prevention programmes? Existing concerns (8) about the safety and effectiveness of influenza vaccines, especially in children under two years, should be addressed in more standardized studies in order to provide clearer vaccination guidelines.

References

1. Centers for Disease Control and Prevention (CDC). Early estimates of seasonal influenza vaccine effectiveness – United States, january 2013.  MMWR Morb Mortal Wkly Rep. 2013;62:32-5.
2. Salleras L, Navas E, Torner N, Prat AA, Garrido P, Soldevila N, Domínguez A. Economic benefits of inactivated influenza vaccines in the prevention of seasonal influenza in children. Hum Vaccin Immunother. 2013 ;9.
3. Cochrane Database Syst Rev. Vaccines for preventing influenza in healthy children. 2012;8:CD004879.
   
4. Prutsky GJ, Domecq JP, Elraiyah T, Wang Z, Grohskopf LA, Prokop LJ, Montori VM, Murad MH. Influenza vaccines licensed in the United States in healthy children: a systematic review and network meta-analysis (Protocol). 2012 ;1:65.
5. Osterholm MT, Kelley NS, Sommer A, Be- longia EA. Efficacy and effectiveness of influ-enza vaccines: a systematic review and meta- analysis. Lancet Infect Dis 2012;12:36-44.
6. Belshe RB, Mendelman PM, Treanor J, et al. The efficacy of live attenuated, cold-adapted, trivalent, intranasal infl uenzavirus vaccine in children. N Engl J Med 1998; 338: 1405–12
7. Vaccines against influenza. Who position paper. Wkly Epidemiol Rec. 2012;87:461-76.
8. Rowhani-Rahbar A, Klein NP, Baxter R. Assessing the safety of influenza vaccination in specific populations: children and the elderly.  Expert Rev Vaccines. 2012 ;11:973-84.

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