New Study Compares Safety Profile of mRNA Vaccines with Influenza Vaccines

Min Seo Kim, MD

According to a new study, mRNA vaccination revealed no significant safety concerns in real-world settings. In fact, compared to influenza vaccines, mRNA COVID-19 vaccines showed an overall safety profile that patterned a lower risk of serious adverse events following immunization (AEFI).

This study focused on the comparative safety of mRNA COVID-19 vaccines to influenza vaccines. A pharmacovigilance analysis of WHO international data base conducted by a team of investigators including, Min Seo Kim, MD, College of Medicine, Korea University, Samsung Advanced Institute for Health Sciences and Technology (SAIHST), Sungkyunkwan University, Samsung Medical Center.

“To the best of our knowledge,” investigators wrote, “this is the first post-implementation pharmacovigilance study to investigate a diverse range of adverse reactions and provide comparative views for COVID-19 mRNA vaccines and influenza vaccine.”

The Results

The safety profile of novel mRNA COVID-19 vaccines varied from the safety profile of influenza vaccines. Systemic reactions like chill, myalgia, and fatigue appeared to be more noticeable with the mRNA COVID-19 vaccine, whereas the influenza vaccine showed more injection site reactogenicity events.

Investigators found that mRNA COVID-19 vaccines displayed a significantly higher risk for a few manageable cardiovascular complications including hypertensive crisis, and supraventricular tachycardia, compared with the influenza vaccines.

Although a higher risk was found for these cardiovascular complications, the mRNA COVID-19 vaccines showed lower risk of neurological complications like syncope, neuralgia, loss of consciousness, guillain-barre syndrome, gait disturbance, visual impairment, and dyskinesia, compared with the influenza vaccines.

Overall, the survival rate was higher among vaccinated individuals compared with those who were not vaccinated.

Individuals who had been vaccinated with the mRNA COVID-19 vaccine experienced fewer deaths than those not exposed to the vaccine (IC 0.25, -1.66; ROR, 0.38; 95% CI, 0.31-0.46). Individuals who had been vaccinated with the influenza vaccine also experienced fewer deaths than those who had not received the influenza vaccine (IC 0.25, -2.22; ROR, 0.26; 95% CI, 0.21-0.31).

The Motivation

The mRNA vaccines are based on new technologies that had not been available to the general population until the COVID-19 pandemic. While each vaccine had extraordinarily encouraging efficacy in the clinical trials, there have also been concerns about their safety in real-world settings.

There has been a high volume of research conducted on the 2 mRNA COVID-19 vaccines developed by Pfizer-BioNTech and Moderna, however, comparing the safety profile of mRNA vaccinated individuals with otherwise vaccinated individuals enabled a more relevant assessment of the safety of mRNA vaccination, according to investigators.

So far, the previous studies involving the mRNA COVID-19 vaccines have mainly looked at the comparison between vaccinated and unvaccinated control. Investigators said this could possibly have highlighted the adverse event risks with mRNA COVID-19 vaccination.

The Study

Investigators conducted a large post-implementation pharmacovigilance using VigiBase, a World Health Organization (WHO) global deduplicated individual case safety reports (ICSR) database.

This database has collected adverse event reports from more than 130 countries and 23 million ICSRs since its beginning in 1967. Any medical event that followed immunization and did not have a causal relationship with the usage of the vaccine was described as an adverse event following immunization.

Investigators gathered adverse events following immunization cases that occurred from the beginning of 2020-January 2021. This included any adverse event following immunization associated with the 2 mRNA COVID-19 vaccines as well as influenza vaccines for comparison.

Of the reports collected from clinical trials, 0.5% experienced an adverse event following immunization with one of the mRNA COVID-19 vaccines and 4.8% experienced and adverse event following immunization with an influenza vaccine.

The results indicate that even though there are variations among the types of risks associated with the different vaccines, the overall safety profile of the mRNA COVID-19 vaccines display a lower risk for serious adverse events following immunization compared with the influenza vaccines.

This study, “Comparative safety of mRNA COVID-19 vaccines to influenza vaccines: a pharmacovigilance analysis of WHO international database”, was published in the Journal of Medical Virology.