It is well known that there are infinitely many primes of the form $a^2+b^2$ (namely all primes congruent to $1$ modulo $4$). On the other hand, Euler raised the problem as to whether there are infinitely many primes of the form $a^2+1$, which is still open (a positive answer is a special case of Bunyakovsky's conjecture). I am wondering whether there are known results in between these cases.

To be precise, I am interested in the following problem: Are there infinitely many primes $p$ of the form $a^2+b^2$ such that $b$ is bounded by a (slowly growing) function of $p$, for example $b = o(\sqrt{p})$?