(HealthDay News) — Breakthrough severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections among fully vaccinated healthcare workers are mainly mild or asymptomatic, according to a study published online July 28 in the New England Journal of Medicine.
Moriah Bergwerk, M.B., B.S., from the Ministry of Health in Israel, and colleagues identified SARS-CoV-2 breakthrough infections by performing an evaluation of symptomatic healthcare workers or those with known infection exposure. Patients with breakthrough infection with antibody titers obtained within a week prior to detection of SARS-CoV-2 were matched with four to five uninfected controls.
The researchers identified 39 SARS-CoV-2 breakthrough infections among 1,497 fully vaccinated healthcare workers. Neutralizing antibody titers were lower in case patients during the peri-infection period than in matched uninfected controls (case-to-control ratio, 0.361). There was an association noted for higher peri-infection neutralizing antibody titers with lower infectivity. Of the breakthrough cases, most were mild or asymptomatic, but persistent symptoms (more than six weeks) occurred in 19%. In 85% of samples tested, the B.1.1.7 (alpha) variant was found. Overall, 74% of case patients had a high viral load at some point during their infection; only 17 of these patients (59%) had a positive result on concurrent antigen-detecting rapid diagnostic testing. There were no reports of secondary infections.
“Although the BNT162b2 vaccine is extremely effective, rare breakthrough infections carry an infectious potential and create a special challenge, since such infections are often asymptomatic and may pose a risk to vulnerable populations,” the authors write.
