The following is a summary of “Incidence and Predictors of Breakthrough and Severe Breakthrough Infections of SARS-CoV-2 After Primary Series Vaccination in Adults: A Population-Based Survey of 22575 Participants,” published in the May 2023 issue of Infectious Diseases by DeSantis, et al.
Breakthrough infections of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have been well-documented. For a study, researchers sought to estimate the incidence of breakthrough infections across different waves of the pandemic and identify predictors of breakthrough and severe breakthrough infections, defined as those requiring hospitalization.
A total of 89,762 participants underwent longitudinal antibody surveillance. Incidence rates were calculated based on the total person-days contributed by the participants. Logistic regression analysis, adjusted for age and corrected for bias, was used to identify multivariable predictors of breakthrough and severe breakthrough infections.
The incidence of breakthrough infections per 10,000 person-days was estimated at 0.45 (95% CI, 0.38-0.50) during the pre-Delta wave, 2.80 (95% CI, 2.25-3.14) during the Delta wave, and 11.2 (95% CI, 8.80-12.95) during the Omicron wave. Factors associated with an increased risk of breakthrough infections included Hispanic ethnicity (odds ratio [OR] = 1.243; 95% CI, 1.073-1.441 compared to non-Hispanic white), larger household size (OR = 1.251 [95% CI, 1.048-1.494] for 3-5 people vs. 1 person and OR = 1.726 [95% CI, 1.317-2.262] for more than 5 people vs. 1 person), rural living (OR = 1.383; 95% CI, 1.122-1.704 vs. urban living), receiving Pfizer or Johnson & Johnson vaccines compared to Moderna, and having multiple comorbidities. Among the 1,700 breakthrough infections, 1,665 were reported on severity, with 112 (6.73%) classified as severe. Predictors of severe breakthrough infections included higher body mass index, Hispanic ethnicity, vaccine type, asthma, and hypertension.
The incidence of breakthrough infections was significantly higher during the Omicron-dominant wave than earlier waves. Certain subgroups showed a higher burden of severe breakthrough infections. The findings highlighted the need for ongoing monitoring and targeted interventions to mitigate the impact of breakthrough infections.