I will be visiting Spain soon and there is a rule in place that US citizens must present proof of vaccination (or other forms of documentation). Spain has mandated that the initial vaccine "expires" after 270 days and therefore you are required to get a booster. I have indeed received my booster but this was also more that 270 days ago for me. So my question is, does the 270 day expiration also apply to booster shots? As in, do I need to receive another booster since my last one was 290 days ago? Thanks!