A: It is generally recommended NOT to pretreat with fever reducers prior to vaccine administration, but if you develop a fever or feel uncomfortable after the vaccine you can take over the counter medicines. Pretreating may decrease the immune response to the vaccine.
Acetaminophen and ibuprofen work by dampening the immune response. Ibuprofen is in a class of therapeutics called nonsteroidal anti-inflammatory drugs (NSAIDs). It works by inhibiting the COX-1 and COX-2 proteins that are found in immune cells such as macrophages. COX-1 and COX-2 generate prostaglandins that act as immune signalers to cause inflammation. Acetaminophen works by reducing levels of prostaglandins (although interestingly the exact mechanism of acetaminophen has not been figured out despite its long and widespread use). By inhibiting this pathway by taking over the counter agents, immune cells are less activated.
There have been clinical research that tested fever reducers aka antipyretic agents with administration of a vaccine. In some trials, the levels of antibodies generated by vaccines were reduced when an antipyretic agent was taken prior to vaccine administration. There were still antibodies generated at levels that were protective, but the levels were less. Taking fever reducers prior to the vaccines resulted in the vaccine not generating the full potential of the immune response and protective antibody generation. Taking antipyretic agents after receiving the vaccine, such as 4 hours later, did not have this effect. Also this reduction of antibodies was more commonly observed with initial vaccine shots and not observed with booster injections.
Please note the information contained here for informational purposes and is not medical advice. Please contact your health care provider for advice especially if you take chronic administration of anti-inflammatory agents for disease.
Current recommendation from the CDC is not to pretreat with antipyretic agents but it is acceptable to take OTC drugs to alleviate symptoms post vaccination. This recommendation has changed over time as some studies have shown decreased antibody responses to vaccines with pre-treatment with antipyretic agents. Taking OTC medications for fever after vaccination does not impact antibodies levels.
Nice review article of trials that tested antipyretic agents with vaccination
Review of mechanism of action for acetaminophen and prostanoid pathway (with nice illustration)
