Coefficient of variation of binomial sum

A vaccine, when it is administered to an individual, produces no side effects with probability $\frac{4}{5}$, mild side effects with probability $\frac{2}{15}$ and severe side effects with probability $\frac{1}{15}$. Assume that the development of side effects is independent across individuals. The vaccine was administered to $1000$ randomly selected individuals. If $X_1$ denotes the number of individuals who developed mild side effects and $X_2$ denotes the number of individuals who developed severe side effects, then the coefficient of variation of $X_1+X_2$ equals __________ (round off to $2$ decimal places)