TUESDAY, Dec. 28, 2021 (HealthDay News) — Full COVID-19 vaccination status is associated with a reduced risk for breakthrough infection, while persons with immune dysfunction have an increased risk for breakthrough infection, according to a study published online Dec. 28 in JAMA Internal Medicine.

Jing Sun, M.D., M.P.H., Ph.D., from the Johns Hopkins University Bloomberg School of Public Health in Baltimore, and colleagues identified the incidence rate and incidence rate ratio for COVID-19 breakthrough infection after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccination in a retrospective cohort study. The sample included 664,722 persons who had received at least one dose of a SARS-CoV-2 vaccine between Dec. 10, 2020, and Sept. 16, 2021.

The researchers found that among fully vaccinated individuals, the overall incidence rate for breakthrough infection was 5.0 per 1,000 person-months. After the delta variant became the dominant SARS-CoV-2 strain, the incidence rate increased (incidence rate before versus after June 20, 2021: 2.2 versus 7.3/1,000 person-months). Full vaccination was associated with a reduced risk for breakthrough infection compared with partial vaccination (adjusted incidence rate ratio, 0.72). A breakthrough infection after full vaccination was more likely among older people and women. The rate of breakthrough infection was higher for people with HIV infection, rheumatoid arthritis, and solid organ transplant (adjusted incidence rate ratios, 1.33, 1.20, and 2.16, respectively).

“The findings support the use of alternative vaccine strategies (e.g., additional doses or immunogenicity testing) and nonpharmaceutical interventions (e.g., mask wearing) even after full vaccination for people with immune dysfunction,” the authors write.

Several authors disclosed financial ties to the biopharmaceutical industry.

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