Immune dysfunction linked to 'substantial risk' for breakthrough COVID-19 infection
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Although vaccines reduce the overall risk for COVID-19 regardless of immune status, patients with immune dysfunction are at a “substantial risk” for breakthrough infection versus those without, according to data.
Specifically, the researchers found that patients with rheumatoid arthritis, HIV infection or solid organ transplant had a higher rate of breakthrough infection despite being fully vaccinated against COVID-19.
“Persons with immune dysfunction were largely excluded from SARS-CoV-2 vaccine clinical trials, creating a large evidence gap,” Jing Sun, MD, MPH, PhD, of the Johns Hopkins Bloomberg School of Public Health, in Baltimore, told Healio. “So, our observational study using a nationally representative electronic medical record database provided real-world evidence on risk and incidence rates for breakthrough infection and vaccine effectiveness among these vulnerable populations.”
To analyze the incidence rate, and incidence rate ratio, for COVID-19 breakthrough infection following vaccination in individuals with or without immune dysfunction, Sun and colleagues conducted a retrospective cohort study of data from the National COVID Cohort Collaborative (N3C). According to the researchers, N3C is a partnership overseen by the NIH National Center for Advancing Translational Sciences, which has developed a centralized registry based on electronic medical records including COVID-19 clinical data supplied by academic medical centers across the United States.
The researchers included a total of 664,722 individuals who received at least one dose of a COVID-19 vaccine between Dec. 10, 2020, and Sept. 16, 2021, with 4,436,139 person-months of follow-up, in their sample. Among these individuals, 633,365 — or 95.3% — completed all recommended doses. In all, 35,512 individuals in the total sample — or 5.3% — had immune dysfunction. For this study, immune dysfunction was defined as having HIV infection, multiple sclerosis, RA, solid organ transplant or bone marrow transplant.
Breakthrough infection was defined as COVID-19 contraction on or after the 14th day of vaccination. Infection risk following full or partial vaccination was assessed for patients with and without immune dysfunction using Poisson regression models. The regression models were controlled for study period — before or after the emergence of the delta variant in late June 2021 — as well as full vaccination status, infection prior to vaccination, demographics, geographic location and comorbidities.
According to the researchers, who published their findings in JAMA Internal Medicine, the overall incidence rate for COVID-19 breakthrough infection was 5 per 1,000 person-months among fully vaccinated persons, but was higher after the delta variant became the dominant strain. The incidence rate before June 20, 2021, was 2.2 per 1,000 person-months (95% CI, 2.2-2.2), compared with 7.3 (95% CI, 7.3-7.4) after that date.
Full vaccination was associated with a 28% reduced risk for breakthrough infection, compared with partial vaccination (adjusted IRR = 0.72; 95% CI, 0.68-0.76). Patients with a breakthrough infection after full vaccination were more likely to be older and women. Patients with HIV infection (adjusted IRR = 1.33; 95% CI, 1.18-1.49), RA (adjusted IRR = 1.2; 95% CI, 1.09-1.32) and solid organ transplant (adjusted IRR = 2.16; 95% CI, 1.96-2.38) demonstrated a higher rate of breakthrough infection, compared with those without immune dysfunction.
“As expected, persons with immune dysfunction have a higher incidence rate and higher risk of breakthrough infection after their COVID-19 vaccination, compared to people without immune dysfunction,” Sun said. “Although persons with immune dysfunction have a higher risk of breakthrough infection, we observed there is reduced disease severity in the breakthrough infection cases, compared to the pre-vaccine COVID-19 cases, regardless of patients' immune status.”
“These findings suggest that persons with immune dysfunction still have a substantial risk of COVID-19 infection even after their full vaccination,” she added. “Therefore, continued use of nonpharmaceutical interventions — eg, mask-wearing, social distancing, avoidance of travel and crowds — and alternative vaccine strategies — eg, additional doses or immunogenicity testing — should be recommended in clinical practice.”
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