SARS-CoV-2 vaccine breakthrough infections with the alpha variant are asymptomatic or mildly symptomatic among health care workers

• Published in: Nature communications Vol. 12; no. 1; pp. 6032 - 7
• Main Authors: Rovida, Francesca, Cassaniti, Irene, Paolucci, Stefania, Percivalle, Elena, Sarasini, Antonella, Piralla, Antonio, Giardina, Federica, Sammartino, Josè Camilla, Ferrari, Alessandro, Bergami, Federica, Muzzi, Alba, Novelli, Viola, Meloni, Alessandro, Cutti, Sara, Grugnetti, Anna Maria, Grugnetti, Giuseppina, Rona, Claudia, Daglio, Marinella, Marena, Carlo, Triarico, Antonio, Lilleri, Daniele, Baldanti, Fausto
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 15.10.2021; Nature Publishing Group; Nature Portfolio
• Subjects: 631/250/590/2293; 631/326/596/4130; 692/308/575; Antibodies; Antibodies, Viral - blood; Antigens; Asymptomatic; Asymptomatic Infections - epidemiology; BNT162 Vaccine; Case-Control Studies; Clinical trials; Contact tracing; COVID-19; COVID-19 - diagnosis; COVID-19 - epidemiology; COVID-19 - prevention & control; COVID-19 - virology; COVID-19 Nucleic Acid Testing - statistics & numerical data; COVID-19 vaccines; COVID-19 Vaccines - administration & dosage; Female; Gene sequencing; Genomes; Health care; Health Personnel - statistics & numerical data; Humanities and Social Sciences; Humans; Immunization Schedule; Incidence; Infections; Lymphocytes T; Male; Medical personnel; multidisciplinary; Prospective Studies; RNA, Viral - genetics; RNA, Viral - isolation & purification; SARS-CoV-2 - genetics; SARS-CoV-2 - immunology; SARS-CoV-2 - isolation & purification; SARS-CoV-2 - pathogenicity; Science; Science (multidisciplinary); Severe acute respiratory syndrome coronavirus 2; Severity of Illness Index; Vaccines; Viral diseases; Whole genome sequencing
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-021-26154-6

Vaccine breakthrough SARS-CoV-2 infection has been monitored in 3720 healthcare workers receiving 2 doses of BNT162b2. SARS-CoV-2 infection is detected in 33 subjects, with a 100-day cumulative incidence of 0.93%. Vaccine protection against acquisition of SARS-CoV-2 infection is 83% (95%CI: 58–93%) in the overall population and 93% (95%CI: 69-99%) in SARS-CoV-2-experienced subjects, when compared with a non-vaccinated control group from the same Institution, in which SARS-CoV-2 infection occurs in 20/346 subjects (100-day cumulative incidence: 5.78%). The infection is symptomatic in 16 (48%) vaccinated subjects vs 17 (85%) controls (p = 0.01). All analyzed patients, in whom the amount of viral RNA was sufficient for genome sequencing, results infected by the alpha variant. Antibody and T-cell responses are not reduced in subjects with breakthrough infection. Evidence of virus transmission, determined by contact tracing, is observed in two (6.1%) cases. This real-world data support the protective effect of BNT162b2 vaccine. A triple antigenic exposure, such as two-dose vaccine schedule in experienced subjects, may confer a higher protection. Several COVID-19 vaccines have shown good efficacy in clinical trials. Here, the authors provide real world effectiveness data in a group of BNT162b2 vaccinated health care workers and find that breakthrough infections are asymptomatic or mild.