Immunization works by sort of ‘tricking’ the body. When the system is injected with a live or modified strain of the virus, it kicks off certain inflammatory reactions and starts preparing antibodies. This, in turn, leads to side-effects some of which include fever, chills, pain at the injection site, nausea and in some cases, tiredness and fatigue.
Now, while most of the side-effects are usually mild and temporary in nature, they happen after you get two complete doses. Some, such as nausea and fatigue can also occur, but the likelihood of the same is not common.
A lot of these symptoms could also mimic the disease itself but should not be confused to be the same.