Acute respiratory infections result in ~ 1.9 million childhood deaths per year, 20% of the deaths are in India. The disease burden of influenza among children in India is ill defined but is likely substantial. Influenza vaccines are in routine use in children in the US, although licensed in India, they are seldom given. Indeed, it is not known whether influenza vaccine efficacy in a tropical developing country will be the same as in developed countries.

Specific Aim 1. Describe influenza vaccine direct and indirect efficacy.

Specific Aim 2. Define influenza clinical disease and outcomes.

In addition to defining the direct and indirect protective effect of influenza vaccine, these studies will develop capacity for influenza virus study and management in second largest country in the world.