Can I get a vaccine after drinking Simo Decoction?
Dec 02, 2025
Source: Cainiu Health
Dr. Sun Lianqing
Introduction
If Si-Mo-Tang is taken only to relieve mild indigestion or bloating, and there are no other symptoms such as fever, vomiting, or diarrhea, and more than 1–2 days have passed since the last dose (by which time the medication has been mostly metabolized), vaccination is generally acceptable. The ingredients in Si-Mo-Tang are mostly mild traditional Chinese herbs that typically do not cause adverse interactions with vaccines or affect the vaccine's immunogenicity.
Generally, if you have taken Simo Decoction (Simo Tang) for mild digestive issues and have no other discomfort, vaccination is acceptable. However, if there are accompanying symptoms of illness, vaccination should be postponed. If in doubt, it is recommended to consult a healthcare provider in advance. Detailed analysis is as follows:
If Simo Decoction was taken solely to relieve mild indigestion or bloating, and there are no other symptoms such as fever, vomiting, or diarrhea, and more than 1–2 days have passed since the last dose—by which time the medication has mostly been metabolized—vaccination is generally safe. The ingredients in Simo Decoction are typically mild traditional Chinese herbs that usually do not interact negatively with vaccines or affect the vaccine's immunogenicity.
However, if Simo Decoction was taken due to an acute gastrointestinal condition (such as severe diarrhea or vomiting), or if symptoms like fever or fatigue persist during treatment, vaccination should be delayed. During illness, immune function may be compromised; administering a vaccine could worsen symptoms and potentially interfere with the normal production of antibodies. Vaccination should be rescheduled until full recovery and after discontinuation of the medication.
Prior to vaccination, inform the doctor about your use of Simo Decoction and your current health status. If new symptoms develop during medication, promptly communicate with your doctor to adjust the vaccination schedule. After receiving the vaccine, remain under observation for 30 minutes and only leave once no adverse reactions are noted, ensuring safe administration.
