Skip to Main Content
Skip Nav Destination

CDC updates clinicians on COVID-19 vaccines, safety monitoring, patient questions

March 10, 2021

Editor's note:For the latest news on COVID-19, visit 

All authorized and recommended COVID-19 vaccines have demonstrated high efficacy against severe COVID-19, and they have undergone the most intensive safety monitoring in U.S. history, federal health officials said Tuesday.

During a Centers for Disease Control and Prevention (CDC) webinar, clinicians reviewed COVID-19 vaccine safety and effectiveness as well as strategies to address patient questions and concerns about the Moderna, Pfizer-BioNTech and Janssen/J&J vaccines.

Patients can expect to experience — and should be counseled about — common symptoms after vaccination, said Tom Shimabukuro, M.D., M.P.H., M.B.A., vaccine safety team lead for COVID-19 response at the CDC.

He said the mRNA vaccines from Moderna and Pfizer-BioNTech are “fairly reactogenic.” Vaccine recipients can experience pain and systemic reactions such as headache, fatigue, myalgia, chills, fever, joint pain or nausea, especially after the second dose. These symptoms are consistent with what was observed during clinical trials.

Deaths after vaccination have been reported, but Dr. Shimabukuro said no safety signals or concerning patterns have emerged. Among the deaths that have been investigated, none have been causally linked to the vaccine, according to a report in Morbidity and Mortality Weekly Report.

Details on COVID-19 vaccine safety and monitoring presented during the webinar were based on analysis from mid-February, when 55 million people had received one dose of any COVID-19 vaccine.

Experts also highlighted the following:

  • Efficacy in preventing hospitalization was 89% or greater for all vaccines.
  • No vaccinated person died due to COVID-19 during the trials. There were eight COVID-19-associated deaths in placebo recipients.
  • The Vaccine Adverse Reporting System (VAERS) found that of 104,000 reports for both mRNA vaccines combined, 94% were classified as nonserious. That number is similar to what typically is observed with other vaccines administered to adults (e.g., flu, shingles, pneumonia).
  • Anaphylaxis reports were rare: 4.7 cases per million doses of Pfizer-BioNTech vaccine administered and 2.5 cases per million following the Moderna vaccine (from mid-December 2020 to mid-January 2021).
  • There have been no unexpected pregnancy or infant outcomes related to COVID-19 vaccination during pregnancy. (Pregnant women were not included in preauthorization clinical trials.) Most VAERS reports involved adverse events such as local and systemic reactions in people who were not pregnant.

Information also was presented on phase III trials. Janssen/J&J vaccine phase III trial results are not comparable with the mRNA vaccines because the trial was conducted under different conditions (calendar time, geography, etc.), according to Kathleen Dooling, M.D., M.P.H., CDC medical officer and co-lead, Advisory Committee on Immunization Practices COVID-19 Vaccines Work Group, COVID-19 Response.

Use of the one-dose Janssen/J&J vaccine is an effective strategy, Dr. Dooling said. The product allows for jurisdictional flexibility, supports rapid vaccination and increases in population immunity, does not single out any group, and allows individuals to be vaccinated with the earliest vaccine available.

Safety monitoring

The CDC is using established and new safety monitoring systems, including the v-safe system, a new smartphone-based active surveillance program it implemented for the COVID-19 vaccine. Providers are encouraged to offer it to patients, who can enroll online.

Safety monitoring also is ongoing in pregnant women and includes the v-safe COVID-19 Vaccine Pregnancy Registry — for v-safe participants who report vaccination in the periconception period. The registry is studying potential health effects like pregnancy outcomes, complications and problems with newborns.

Vaccine confidence

Health officials offered guidance on how clinicians can address vaccine hesitancy in their patients.

Public confidence in and acceptance of the COVID-19 have increased in the last few months, according to Kaiser Family Foundation research. In February, 55% were vaccinated or planning to get the vaccine when available, up from 34% who had expressed willingness to be vaccinated as of December. The percentage of those taking a wait-and-see approach was 22% in February, down from 39% in December.

“Despite these gains, hesitance remains an issue of those respondents who remain in the wait-and-see group,” said Lt. Stephen Perez, Ph.D., clinical lead, Vaccine Confidence Team, CDC.

Brief and consistent messaging is key, he said.

Elements of effective vaccine conversations include empathy and understanding, being prepared for questions, making a strong recommendation, addressing misinformation and proactively explaining side effects. Culturally responsive messaging also is important. Providers can make information available through channels and in formats and languages for diverse audiences, and establish community partnerships.

Close Modal

or Create an Account

Close Modal
Close Modal