COVID-19 Second Dose “Side Effects”

Both COVID-19 vaccines authorized by the FDA for emergency use in the United States elicit a strong immune response and are highly protective. In order to achieve the (exceptional) levels of efficacy touted by clinical trials, it is crucial that recipients receive two doses through immunizations given several weeks apart. The first dose primes the immune system, teaching it to recognize the spike proteins that make the coronavirus unique, thereby beginning the process of building immunity. The second dose boosts and solidifies the immune response to ensure that the body is ready to conquer SARS-CoV2 if it is encountered.

Particularly following the second dose, it is common for recipients to feel symptoms of the body’s immune response to the vaccine. Generally arising within 12-24 hours after the vaccine is administered, symptoms are most often mild and may include pain, swelling, or redness at the injection site, or flu-like symptoms. This is completely normal and should be no cause for alarm. Similarly, worry not if you find yourself in the fortunate minority and experience not a single symptom; older persons are less likely than younger folks to have symptoms and this should have no bearing on the effectiveness of your vaccine. Happily, symptoms of your body’s successful immune response to vaccination typically vanish within 12-36 hours.

CDC expressly recommends against pre-medicating with over-the-counter medications (anti-fever, anti-inflammatory, analgesic, and/or antihistamine) in anticipation of possible post-vaccination symptoms.

While the issue of pre-medication was not specifically investigated in the COVID-19 vaccine clinical trials for either Pfizer or Moderna, there are studies that suggest that pre-medication with antihistamines/antipyretics/NSAIDs may dampen the natural and desired immune response to vaccination.

CDC recommendations:

• If you take Tylenol, NSAIDs (like ibuprofen), or antihistamines (like Claritin) routinely, continue to do so and do not alter your usual medication regimen in anticipation of the vaccine.
• Avoid taking Tylenol, NSAIDs, or antihistamines as pre-medication in anticipation of future symptoms related to the vaccine.
• After your vaccine, if you do have symptoms that are sufficiently uncomfortable to warrant medication according to your usual standards, feel free to take over-the­-counter medications as needed. *

*If you have questions about which over-the-counter medications are safe for you to take based on your current diagnoses, medical history, or current medication regimen, please contact your primary care provider or pharmacist.