As any parent knows, youngsters are experts at spreading infectious diseases, both among themselves and to adults. So it stands to reason that vaccinating children against the flu would go a long way toward protecting all members of a population. To evaluate the effect of vaccinating children aged six months to 18 years on flu cases in the general population, VIDI member Dr. Ira Longini and colleagues used statistical methods to examine a variety of vaccination strategies for both seasonal and pandemic flu outbreaks.
The researchers modeled the spread of influenza in Los Angeles County, and extrapolated those results to the rest of the U.S. They looked at the effects of various vaccination strategies on flu rates in different age groups as well as in the population as a whole. Using a statistical simulation based on random chance, they modeled the effects of a variety of cases, including nasal spray or intramuscular flu vaccines, coverage levels of 30, 50, or 70 percent children vaccinated, a close or poor match of the vaccine strain to circulating strains, and a range of transmission rates.
The researchers found that in all circumstances examined, the higher the vaccine rate in children, the lower the number of flu incidences in the overall population and in age-specific groups. Approximately 19 million flu cases in a mild influenza season (low rates of transmission) or nearly 100 million cases in a pandemic flu season (high transmission rates) in the U.S. could be prevented if 70 percent of children were vaccinated. These findings may have special importance for pandemic H1N1, as health officials will soon need to decide how to allocate the H1N1 vaccine.
Strategies for pandemic and seasonal influenza vaccination of schoolchildren in the United States. Basta NE, Chao DL, Halloran ME, Matrajt L, Longini IM Jr. Am J Epidemiol. 2009 Sep 15;170(6):679-86