Pfizer Reports Only Mild-to-Moderate Side Effects of COVID-19 Vaccine in Late-Stage Trial

Pfizer reported early safety data yesterday from its phase 3 COVID-19 vaccine trial, saying the vaccine prompted mostly mild to moderate adverse reactions in patients.

In an investor call yesterday, Kathrin Jansen, Pfizer’s head of vaccine R&D, presented interim safety results from participants who had received one or two 30-mcg doses of BNT162b2 or a placebo as of Aug. 27.

Thirty-eight percent of participants ages 18-64 given one dose of the vaccine experienced fatigue, while 35 percent experienced headache and 15 percent experienced chills, she said. In addition, approximately 11 percent of patients experienced fever, chills and joint pain. These numbers were lower among participants aged 65-85.

In addition, 36 percent of participants ages 18-64 given a second dose experienced fatigue, 28 percent experienced headache and 18 percent experienced muscle pain. Again, these percentages were lower among those in the older age cohort.

While most adverse events between the groups were mild or moderate, more patients who received two doses experienced more serious cases than those only given one, Jansen said.

She noted that an independent data monitoring committee conducts weekly reviews of the safety data and it has not raised any concerns to date.

Meanwhile, Pfizer announced via Twitter yesterday that the trial has hit its initial enrollment target of 30,000 participants, making it the first phase 3 COVID-19 vaccine study to reach full enrollment. Pfizer and BioNTech, the vaccine’s developer, have already submitted a protocol to the FDA to expand enrollment to 44,000 patients (DID, Sept. 14).  As of Sept. 14, 12,000 participants had received a second dose. — Jordan Williams