Raising Awareness of Reactogenicity Crucial in COVID-19 Vaccine Rollout

Public perception about potential side effects could complicate efforts to reassure the public about safety in the rollout of the first vaccines against the coronavirus disease 2019 (COVID-19), some health officials say.

Phase 3 trials have demonstrated safety and immunogenicity of the first vaccine candidates, including messenger RNA (mRNA) vaccines from Pfizer/BioNTech and Moderna. Still, some adverse events are expected.

“For some vaccines (mRNA), if you experience reactogenicity after the first shot, it’s generally worse for the 2nd (booster) dose,” Deborah Fuller, professor of microbiology at University of Washington School of Medicine, told Contagion®. “The biggest concern to me is that people who experience a degree of reactogenicity after their first shot may not come back for the booster dose.”

Fuller said side effects of the COVID-19 vaccines are similar to other vaccines, including pain and soreness at the injection site, slight swelling, and possible fever.

“In some cases, a person may not feel well enough to go to work,” Fuller said. “This actually indicates the vaccine is working. The immune responses we make to a pathogen when we’re exposed is what makes us feel like we’re coming down with something. Vaccines mimic an infection without causing a disease so this reactogenicity is normal.”

On Thursday, the U.S. Food and Drug Administration will hold a public forum on BNT162b2, the two-dose messenger RNA (mRNA) vaccine from Pfizer and BioNTech. Data submitted to the FDA showed that adverse events included fever, fatigue, headache, chills, vomiting, diarrhea, and new or worsened muscle/joint pain.

Investigators reported 3 serious adverse events related to the vaccine: shoulder injury, ventricular arrhythmia, and lymphadenopathy.

Investigators studying the Moderna COVID-19 vaccine, mRNA-1273 reported no serious adverse events during the trial or at day 57.

While serious adverse events are rare and usually temporary, health officials are bracing for possible responses from the public and working to manage expectations and educate the public to ward off fear and a potential backlash against the vaccines.

An article in Science noted that while fewer than 2% of recipients of the Pfizer and Moderna vaccines developed severe fevers, that would amount to 700000 of the 35 million people expected to receive the vaccines globally by the end of December. Severe fever and aches could be alarming for those who aren’t prepared for them and could exacerbate vaccine hesitancy driven by the speed of development and other uncertainties.

Clinicians should be prepared to answer questions from patients and distribute pamphlets explaining reactogenicity, what to expect within the range of normal effects and what might be considered a severe reaction will likely be distributed with the vaccine, similar to other vaccines.

“For a new vaccine, I think it will be important that clinicians review the key points with their patients – what is in the range of typical and what to do if they experience something more severe,” Fuller said. “With a mass vaccination, clinics will probably need a hot line for people to call if they experience any reactions of concern. Clinicians will also need a system of follow-up with their patients to ensure the concerns about reactogenicity doesn’t put them off getting the vaccine or coming back for the boost.”