Effectiveness of mRNA BNT162b2 Covid-19 vaccine up to 6 months

No. It means that every vaccinated person has a 53% reduction in their chance of catching covid-19.

More importantly, this study found that after 6 months, protection against being hospitalized was still very high (93%). So, while vaccinated people may spread it, they're very unlikely to end up in the hospital or die from it.

No, they are not. They still have protection from disease but they may get infected.