Please don’t listen to the anti-vaxxers, vaccines are safe, the US-funded ones are 99.9998% reliable to prevent symptomatic infection (literally, read the literature - 1 in 50,000 test subjects did not seem to get antibodies, which could be due to a number of reasons, most likely human error).
The problem sits in the SinoVac/SinoPharm/CoronaVac and other Chinese funded, they’ve proven to be 50% (peer reviewed) to 80% (according to Chinese propaganda) reliable to prevent symptomatic infection, Sputnik V, the Russian one is 90% reliable. This applies to places like some Eastern European and other third world countries that didn’t fund a proper vaccine and rely on the Belt and Road or COVAX project to give them low cost vaccines. The EU is also considering those vaccines for the same reason.
Do note the all vaccines, although reliable, can have some minor side effects and some may trigger allergic reactions, but that is the case for ANY vaccine, from Tetanus to Polio to HPV to COVID. Vaccines also do not work against big variations in the pathogen although the mRNA vaccines have all proven to be reliable against extant COVID-19 variations.
It is also possible that you do not generate antibodies for some unknown reason. It’s also possible that human error (eg bad injection or letting the vaccine out of the freezer or expire) could mean your vaccine doesn’t work properly. That is why you need herd immunity which the US is well above the levels so outbreaks won’t happen anymore.