The difference between cat vaccines of 21 days and 28 days is the efficacy. The longer the time, the less the efficacy. It is best to get the second dose of vaccine between 21 and 28 days, otherwise it is easy to cause the previous vaccine to The efficacy of the medicine disappears and it loses its effect. Cats can start to be vaccinated when they are two months old. During the period of vaccination, the cat cannot be bathed. At the same time, it is necessary to supplement nutrition and improve immunity.