By booster vaccine nowadays, we generally refer to the new coronavirus vaccine booster shot. The inactivated vaccines against the new coronavirus used in China have a good safety profile. Current studies on booster vaccination show that no serious adverse reactions related to the vaccine have been found in adults aged 18 years and above (including the elderly aged 60 years and above) after vaccination, with the most common adverse reaction being pain at the injection site. Since vaccination booster shots cause local skin damage and drug irritation, some people may experience local reactions at the vaccination site, such as mild redness, swelling, pain, rash, itching, and so on. It is recommended that you do not take a shower within 24 hours of receiving the vaccination booster shot to avoid causing infection at the site of the needle puncture leading to a worsening of the local reaction. If the redness, swelling and pain are more obvious, you can use iodophor to sterilize the area as prescribed by the doctor to avoid causing infection. Other rare side effects, such as fever and allergic reactions, can usually be relieved on their own, while those with serious symptoms are advised to go to the hospital in time to avoid delaying their condition. Vaccination should be administered as long as your condition permits to avoid serious side effects.