Vaccines are the only way to prevent viral diseases like that caused by Covid 19 infection. Multiple vaccines that can effectively protect against illness caused by Covid 19 virus have already been developed and are being administered to people all over the world. But, a small number of people may get the Covid 19 disease even after being vaccinated. One of the reasons for getting Covid 19 infection after vaccination may be due to a new variant of the virus that the vaccine is not very effective against. Some people may have already been infected by the Covid 19 virus before taking the vaccine doses. Most of the Covid 19 vaccines take a couple of weeks to work, therefore a vaccinated person may become infected with the virus because the vaccine has not had enough time to produce anti-Covid 19 antibodies. Frontline workers and healthcare professionals may catch the disease even after being vaccinated due to continuous exposure to Covid 19 patients. Although vaccines are not 100 percent efficient at preventing Covid 19 virus infection, the risk of patients falling severely ill, being hospitalized or dying is reduced to a great extent because of the protection offered by vaccines. A vaccinated person is likely to suffer a mild Covid 19 illness or be entirely asymptomatic. Therefore, it is important to remember that the vaccines currently being used against Covid 19 may not prevent infection by the Covid 19 virus, the transmission of the virus but will protect against serious disease and fatalities.