Published originally on TrialSite New Staff on Apr. 28, 2022, 7:30 p.m.

Belgium researchers embarked on a study that hopefully can shape future vaccination programs targeting COVID-19. In a recently published study, these scientists assessed the risk factors associated with developing COVID-19 after vaccination. The results of which were presented at this year’s European Congress of Clinical Microbiology & Infectious Diseases (ECCMID) in Lisbon, Portugal, (23-26 April).  It turns out the mRNA-based vaccines afford more protection than those immunized with the AstraZeneca/Oxford viral vector vaccine.  

So, what are breakthrough infections? They are characterized when the pathogen evades vaccine-induced bodies, thereby infecting the inoculated person. In this study, Dr. Veerle Stouten and colleagues at Sciensano, the National Public Health Institute of Belgium, investigated the incidence of breakthrough infections associated with four different COVID-19 vaccine brands. These brands included Pfizer/BioNTech (BNT162b2), Moderna (mRNA-1273), Oxford/AstraZeneca (ChAdOx1) and Janssen (Ad26.COV2.S).

The Study

More than 80% of adults in Belgium were fully vaccinated (received two doses) by August 11, 2021.

The study included all people in Belgium aged 18-plus who were fully vaccinated against COVID-19 between February 1 and December 5, 2021. The 8,062,000 participants were followed up for an average of 150 days, from 14 days after their second dose.

4.6% of the participants (373,070) were reported to have a breakthrough infection. This figure does not, however, take into account how long each participant was followed-up after the study. When this is factored in, the incidence rate is 11.2 per 100 person-years. This means that if participants were followed up for one year, 11.2 would be expected to develop a breakthrough infection. 

Results

Researchers share that “breakthrough infections were more common in those who had received viral vector vaccines than mRNA vaccines. Those who had previously had Covid had a lower risk of breakthrough infections.”

Overall, those vaccinated with a viral vector vaccine (Oxford/AstraZeneca or Janssen) had a higher risk of a breakthrough infection than those vaccinated with an mRNA vaccine (Pfizer/BioNTech or Moderna).

In addition, “There was a higher incidence of breakthrough infections in younger age groups (18-64 year olds) than in older age groups (65-84 or 85-plus year olds), which might be due to differences in social behavior.”

Natural immunity also comes into play here. Researchers observed from the analysis that “those with a prior COVID-19 infection before vaccination were 77% less likely to have a breakthrough infection than those who hadn’t had Covid previously.”

Significant Implications

Such information regarding breakthrough infections can be helpful when designing vaccination programs, including decisions about who would benefit most from a booster dose and the timing and type of vaccine to be used. 

Dr. Stouten adds: “We identified risk factors associated with breakthrough infections, such as vaccination with adenoviral-vector vaccines, which could help inform future decisions on booster vaccination strategies internationally.

Lead Research/Investigator

Dr. Veerle Stouten, Department of Epidemiology and Public Health, Sciensano, Brussels, Belgium

Belgium researchers embarked on a study that hopefully can shape future vaccination programs targeting COVID-19. In a recently published study, these scientists assessed the risk factors associated with developing COVID-19 after vaccination. The results of which were presented at this year’s European Congress of Clinical Microbiology & Infectious Diseases (ECCMID) in Lisbon, Portugal, (23-26 April).  It turns out the mRNA-based vaccines afford more protection than those immunized with the AstraZeneca/Oxford viral vector vaccine.  

So, what are breakthrough infections? They are characterized when the pathogen evades vaccine-induced bodies, thereby infecting the inoculated person. In this study, Dr. Veerle Stouten and colleagues at Sciensano, the National Public Health Institute of Belgium, investigated the incidence of breakthrough infections associated with four different COVID-19 vaccine brands. These brands included Pfizer/BioNTech (BNT162b2), Moderna (mRNA-1273), Oxford/AstraZeneca (ChAdOx1) and Janssen (Ad26.COV2.S).