New CDC Study Shows Positive Results for COVID-19 Vaccine Safety


Pharmacists can play an important role in educating the public about the safety of the Pfizer and Moderna COVID-19 vaccines.

The Pfizer-BioNTech and Moderna COVID-19 vaccines received Emergency Use Authorization (EUA) on December 11, 2020 and December 18, 2020, respectively.1 A new CDC study is revealing positive information that both COVID-19 vaccines are safe.

The Advisory Committee on Immunization Practices initially recommended in their interim guidance that both health care personnel and residents of long-term care facilities (LTCFs) be offered the COVID-19 vaccine in the initial phase of the vaccination program.2 Vaccine safety monitoring has involved the Vaccine Adverse Event Reporting System (VAERS) and v-safe (active surveillance system).1,3 The v-safe is a smartphone-based surveillance tool that uses text messaging and web surveys to provide personalized health check-ins after receiving a COVID-19 vaccine, and individuals can let the CDC know if they are experiencing any adverse effects.3

The CDC performed a descriptive analysis of safety data for the Pfizer and Moderna COVID-19 vaccines from VAERS and v-safe during the first month of vaccination (December 14, 2020-January 13, 2021). Additionally, 13,794,904 COVID-19 vaccines were administered during the study timeframe.1 There were 6994 adverse event reports through VAERS, of which 90.8% were classified as nonserious and 9.2% were classified as serious.1 The most frequently reported adverse effects were headache (22.4%), fatigue (16.5%), and dizziness (16.5%). There were 113 deaths reported to VAERS, of which 65% were among LTCF residents; however, the available information from the surveillance systems indicated the deaths were not associated with the vaccines.1

Rare cases of anaphylaxis after receiving both vaccines were reported (4.5 reported cases per million doses administered).1 The median age of individuals reporting adverse events through VAERS was 42 years (range = 15-96 years).1

Pfizer COVID-19 vaccine adverse reactions reported to the v-safe system were more frequent after receiving the second dose than after the first.1 Since the Moderna vaccine received its EUA after Pfizer, second dose information was not available at the time of the study for Moderna.1

During the study period, v-safe enrolled 1,602,065 vaccine recipients who completed at least 1 survey, with 50.8% having received Pfizer, and 49.2% received Moderna vaccines.1 Injection site pain, fatigue, headache, myalgia, and chills were frequently reported through v-safe.1 Study limitations include that the VAERS program is based on passive surveillance so there could be bias and underreporting involved.1 V-safe is a voluntary surveillance system that individuals may not be aware of that requires a smartphone, which can also lead to underreporting due to lack of program knowledge or access.1

Pharmacists can play an important role in dispelling COVID-19 vaccine myths and countering vaccine hesitancy. Additionally, pharmacists play a critical role in COVID-19 vaccination especially as the vaccine becomes more widely available through community pharmacies. Pharmacists should report any adverse effects associated with COVID-19 vaccines through VAERS and encourage patients and health care professionals to sign up for v-safe after being vaccinated to assist with safety monitoring.


  • Gee J, Marquez P, Su J, et al. First Month of COVID-19 Vaccine Safety Monitoring—United States, December 14, 2020—January 13, 2021. MMWR Morb Mortal Wkly Rep. ePub: 19 February 2021. DOI:
  • Dooling K, McClung N, Chamberland M, et al. The Advisory Committee on Immunization Practices’ Interim Recommendation for Allocating Initial Supplies of COVID-19 Vaccine—United States, 2020. MMWR Morb Mortal Wkly Rep 2020;69:1857-1859. DOI:
  • CDC. V-safe after vaccination health checker. Updated February 6, 2021. Accessed February 22, 2021.

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