Immunologists and infectious disease experts say it is not unexpected that second-dose reactions to the Pfizer and/or Moderna vaccine are more intense than the first. “The first time the immune system comes into contact with something, it is getting primed” said Purvi Parikh, MD, an immunologist at NYI Langone Health in New York City. “That goes for everything, from vaccines to allergies. It is rare on the first time to have a strong reaction. After that, the immune system recognizes it, so you have a much stronger reaction.”

In both Pfizer’s and Moderna’s phase II trial data, systemic adverse events were reported more frequently after dose 2 than dose 1. For the latter, rates were 54.9% versus 42.2% for placebo after the first dose and 79.4% versus 36.5% for placebo after the second dose. Fever, headache, fatigue, myalgia, arthralgia, and chills were far more common after the second dose compared with the first dose and with all placebo doses.

Most reactions to the vaccine resolve within 36 hours, a much easier course than having COVID-19! It won’t necessarily be easy, but if it was everyone would be doing it.

Stay the course, stay well, mask up, get vaccinated, and stay tuned!