High Prevalence of Delta-Vaccine Breakthrough Infections in Fully Vaccinated Individuals

Strategic Insights -

In a preprint abstract published on medrxiv.org, researchers describe the characteristics of vaccine breakthrough infections (VBI) in fully vaccinated individuals in France during the Delta wave. A total of 1,630 VBI cases from patients fully vaccinated between February and July were included in the study. The analysis revealed that the Delta variant represented 94.1% of the 1,366 samples sequenced, with most cases being symptomatic (mainly mild symptoms) with no difference according to the vaccine strategy. The study found that up to 50% of VBI cases were classified as early-VBI, occurring less than one month after full immunization, and that people aged 14-49 were overrepresented in early VBI cases for certain vaccine strategies.

Key Takeaways:

  • A total of 1,630 VBI cases from patients fully vaccinated between February and July were included in the study.
  • The Delta variant represented 94.1% of the 1,366 samples sequenced.
  • Most VBI cases were symptomatic (mainly mild symptoms) with no difference according to the vaccine strategy.
  • Up to 50% of VBI cases were classified as early-VBI, occurring less than one month after full immunization.
  • People aged 14-49 were overrepresented in early VBI cases for certain vaccine strategies, such as BNT162b2 and mRNA-1273.
  • The median RT-PCR Ct values at diagnosis were significantly different between symptomatic and asymptomatic cases only for the BNT162b2 group.
  • The study highlights the potential for relaxation of barrier gestures to contribute to the spread of VBI in young patients.

Statistics:

  • 94.1% of 1,366 samples sequenced were the Delta variant.
  • Up to 50% of 1,630 VBI cases were classified as early-VBI.
  • 73.92% of BNT162b2 VBI cases occurred in people aged 14-49, compared to 37.87% of non-early VBI cases.
  • 77.78% of mRNA-1273 VBI cases occurred in people aged 14-49, compared to 46.67% of non-early VBI cases.
  • The median RT-PCR Ct values at diagnosis were 17.7 (15.07, 20.51) for symptomatic BNT162b2 cases and 19.00 (16.00, 23.00) for asymptomatic BNT162b2 cases.

Sources:

  • medrxiv.org/content/10.1101/2021.12.05.21267301v1