Is this duplication in constructors with initializer lists really necessary?

Am I using initializer lists correctly in my class? There seems to be a lot of code duplication. If I needed another variable, I'd have to add it in three places.

class MyClass {
public:
    MyClass(
        anotherClass _a,
        std::string _b,
        std::string _c,
        float _d
        )
        : a(_a),
        b(_b),
        c(_c),
        d(_d)
    { }
private:
    anotherClass a;
    std::string b;
    std::string c;
    float d;
};