Genetic Sequencing of Breakthrough Severe Acute Respiratory Syndrome Coronavirus 2 Infections in Fully Vaccinated Healthcare Workers

Abstract

Abstract Introduction Since the identification of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), several efforts have been made to prevent infection, culminating in the development of highly effective vaccines. However, as genetic variants of the virus have emerged, concerns have arisen regarding potential limitations of available vaccines. Methods In this article, we evaluated SARS-CoV-2 breakthrough infections among 520 healthcare workers in a 950-bed hospital from March 1, 2021, to October 31, 2021, and stratified them according to the type of vaccine received. We tested for associations between Alpha and Delta strains of SARS-CoV-2 and clinical characteristics. Results During the study period, only 0.85% of the patients with breakthrough infection vaccinated with messenger RNA (mRNA)-1273 required hospitalization, whereas none of patients vaccinated with BNT162b2 required admission. No association was noted between the variant isolated and the type of vaccination (P = 0.474). The cycle threshold was significantly lower for Delta strain infections compared with Alpha strain infections (P = 0.0144 for gene N1 and P = 0.0271 for gene N2), reflecting a significantly higher viral burden at the time of diagnosis of Delta strain infection. We observed that, at the time of diagnosis, almost all vaccinated patients had developed antispike antibodies, whereas slightly more than half had anti-N antibodies. Discussion We noted that vaccination remains an important preventive measure to protect patients from severe SARS-CoV-2 infection. The mRNA-1273 and BNT162b2 mRNA vaccines seem equally effective in minimizing the severity of breakthrough infections. Serologic patterns suggest that antispike antibodies may be more critical for protection than antinucleocapsid antibodies.