Breakthrough COVID-19 infections were rare in fully vaccinated individuals, but the average breakthrough occurred just under 50 days after complete vaccination.
COVID-19 vaccination has been invaluable in controlling the pandemic. However, vaccine rollout was disproportionate across countries and communities, leading to unmitigated incidence rates that drove the continued mutation of the COVID-19 virus.
The emergence of new COVID-19 variants, as well as the natural waning of vaccine efficacy, has led to breakthrough infections among full vaccinated persons. One study, presented as a poster during the IDWeek 2022 conference, evaluated the rate of breakthrough infections.
The study was conducted in Sangamon County, Illinois, a central region with a rural and urban population of 195000. The investigators utilized data from the Sangamon County Department of Public Health to examine breakthrough infections. Information included total number of COVID-19 infections, type of vaccine received, ages of the infected, and time elapsed after complete vaccination. “Complete vaccination” was defined as 14 days after the second dose of Pfizer-BioNTech or Moderna, or 14 days after a single dose of the Johnson & Johnson COVID-19 vaccine.
The investigators found that 87086 COVID-19 infections were recorded in Sangamon County, with 44.58% of the entire population infected. Of all these infections, 0.036% were breakthrough infections among fully vaccinated persons. The average time to infection after complete vaccination was 49.13 days, with a standard deviation of 23.38.
This county-wide study found breakthrough infections among fully vaccinated persons to be very rare. The study authors credited this low rate to “the high efficacy of the vaccines.”
This study is somewhat limited, as it did not account for breakthrough rate across different variants and specific patient characteristics. However, the recorded high efficacy of vaccines suggests a need to continue refining vaccination strategies to prevent further COVID-19 mutations.
This study, “Local Experience of Breakthrough SARS-CoV-2 Infections After Full Vaccination,” was presented by Ahmed A. Khan, MD, at IDWeek 2022, held October 19-23, 2022, in Washington, D.C.