How to construct one sided CI for Superiority Randomized Controlled Trial?

If your assumption before doing the superiority test is that timely vaccination is more likely to occur with text messages, report the upper limit of the CI on the ratio of the text-messaged group to the non-text-messaged group. This limit is also known as $U$, and will generally be some number above 1, as will your risk ratio. A simple estimate is $$U = frac{p_1}{p_2} ~ exp left( 1.64 sqrt{frac{1-p_1}{n p_1} + frac{1-p_2}{n p_2}} right)$$ where $p_1$ is the proportion of timely-vaccinated people in the text-messaged group, $p_2$ the corresponding proportion in the non-messaged group, and $n$ is the number of subjects. If you have unbalanced data, see Table I and equation 24 here. And if you need a more sophisticated approach (for example, not relying on the normal approximation), see pages 7-10 here.

A word of warning before you continue with your superiority test: is it really appropriate? See here.