In case you're wondering how someone can become infected with COVID-19 after vaccination the answer is simple - immunity doesn't kick in right away. It takes time for vaccines to build up immunity, and the two authorized coronavirus vaccines both require two doses, given several weeks apart, to train the body's immune system. People can be exposed to coronavirus right before being vaccinated, or right after, and there won't be time for the body to develop its defenses. No vaccine is 100% effective, and the makers of coronavirus vaccines are still evaluating whether the shots protect against all infections, or just those that cause symptoms. This is why the CDC and state health authorities continue to advise the vaccinated and unvaccinated public to wear a mask, stay physically distant, wash your hands and avoid social gatherings.