I (female, 25) recently realized my boyfriend's cum (male, 26) looks, feels and tastes way more watery than usual. I began noticing this 2 weeks after he got his third Pfizer shot. I'm a bit hesitant about mentioning this issue ti him, but at the same time I'm worried that his cum might have a negative effect on my health. I have not been vaccinated.

Can this be a side effect of the vaccine? Could this pose any harm to me?