To decide how best to allocate and prioritize vaccines for highly infectious diseases, such as the flu, it’s important to know which groups of people are the most infectious and susceptible to that disease. As with many easily communicable diseases, children seem to be great vectors for spreading the flu, and the 2009 pandemic H1N1 strain was no exception. To better understand the effect of age on H1N1 transmission, VIDD postdoctoral fellow Dr. Jonathan Sugimoto, along with VIDD members Dr. Ira Longini and Dr. Betz Halloran and assistant member Dr. Yang Yang, studied an outbreak of novel H1N1 influenza in a youth camp near Olympia, Wash. in April 2009.
Nearly 100 children from four different schools attended the camp, and Public Health – Seattle King County and the U.S. Centers for Disease Control and Prevention gathered data on how many kids in the camp got sick, and then how many of their family members came down with the flu after the children returned home. Sugimoto and his colleagues then used that data to look at the transmission of clinical H1N1 in the camp and in households. The camp study and other corroborating studies found high rates of secondary transmission among groups of children, such as in schools and camps, but as compared to seasonal flu and previous flu pandemics, Sugimoto and colleagues found lower than expected rates of transmission of H1N1 flu in households. 51 percent of children in the camp got sick, but a lower percentage of the sick children’s family members came down with the flu after being exposed. Part of this is due to the age effect, Sugimoto said, where children appear to be more susceptible to flu in general. But that doesn’t fully explain the low transmission rates they saw in households. One possibility is that analyses of flu transmission may underestimate the number of household members that are already immune to novel H1N1, Sugimoto said.
Sugimoto’s study reinforces the view that influenza vaccines should be heavily targeted toward school-aged children.
Sugimoto JD, Borse NN, Ta ML, Stockman LJ, Fischer GE, Yang Y, Halloran ME, Longini IM Jr, Duchin JS. The Effect of Age on Transmission of 2009 Pandemic Influenza A (H1N1) in a Camp and Associated Households. Epidemiology. 2011 Mar;22(2):180-187.