Babies crying at night after vaccination may be related to fright, excessive hunger, drug reaction, intestinal cramps and so on. 1. Scaring: If the baby is frightened during the daytime when taking vaccination, the baby may not sleep soundly at night and may cry at night. 2. Excessive hunger: some babies may feel hungry after vaccination and may cry in the middle of the night because of hunger. 3. Drug reaction: some babies will be vaccinated, which will cause muscle pain with fever, redness and swelling at the injection site and other discomforts, which is likely to cause babies to cry. 4. Intestinal spasm: If the baby’s gastrointestinal smooth muscle spasm is caused by intestinal spasm, it may cause pain and crying. As you can see, there are many reasons why babies cry at night after vaccination, and if the crying continues unabated, it is recommended to consult a doctor to find out the cause and give appropriate treatment.