Generally, a few hours to 24 hours after the vaccination, some patients may experience local reactions such as redness, swelling, itching and pain at the injection site due to individual differences and the inherent characteristics of the vaccine itself. The extent of redness and swelling after vaccination is generally small, and only a few people have redness and swelling of more than 3 cm in diameter, which may be accompanied by muscle pain to the point of not being able to lift the arm. For some patients with heavy redness and muscle pain, it may be caused by inflammation of the nearby lymph nodes or lymph vessels. In addition, some patients may have swelling or hard nodes after vaccination because the adsorbent in the vaccine is not fully absorbed at the injection site, which may stimulate the growth of connective tissue. However, these reactions are generally idiosyncratic and do not occur in everyone. The time of self-resolution also depends on the individual’s constitution. Redness and swelling infiltration will subside in 48-72 hours; pain, pressure and soreness will subside in 2-7 days; hard nodes will subside in 7 days to 2-3 months; lymph node enlargement and lymphangitis will last from 24 hours to about 7-14 days. Patients with redness and itchiness in the arms after vaccination can be temporarily observed and care should be taken not to scratch the injection site to avoid local infection and aggravation of local discomfort. Patients with redness, swelling and itching that is too extensive or lasts too long may have secondary infection and should seek medical attention and report the situation to the vaccination unit.