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A New England Journal of Medicine Yesterday’s study details groundbreaking COVID-19 infections in 39 of 1,497 fully vaccinated Israeli healthcare workers, most cases being mild or moderate, but 19% of symptoms persist for more than 6 weeks.
A team led by researchers at Tel Aviv University used diagnostic tests, antibody tests, genomic sequencing and contact tracing to assess healthcare workers who were symptomatic or had been exposed to a disease. infected person.
All workers had received a second dose of the Pfizer / BioNTech vaccine 11 days before the start of the study on January 20. The study lasted 14 weeks, during which time Israel experienced its third and largest outbreak of COVID-19 cases.
The researchers also matched workers with COVID-19 and antibody concentrations obtained in the week prior to diagnosis with four or five uninfected controls and used generalized estimating equations to predict average antibody levels and the ratio between the levels in the two groups.
A “special challenge”
In total, 2.6% of healthcare workers have had breakthrough COVID-19 infections, of which 67% were mild and 33% were asymptomatic. The most common symptoms were upper respiratory tract congestion (36%), muscle pain (28%), loss of smell or taste (28%), and fever or chills (21%).
“In this study, we found that although the [Pfizer] the vaccine is extremely effective, the rare breakthrough infections have infectious potential and create a particular challenge, as such infections are often asymptomatic and may pose a risk to vulnerable populations, ”the researchers wrote.
Thirty-one percent of infected workers reported persistent symptoms 14 days after their diagnosis, and 19% reported “long COVID” symptoms of loss of smell, cough, fatigue, weakness, shortness of breath, or muscle pain for more than 6 years. weeks. None were hospitalized. Of the 23% of workers who took leave of absence beyond the mandatory 10-day quarantine, four returned to work within 2 weeks and one still had not returned after 6 weeks.
The Alpha (B117) SARS-CoV-2 variant, which was dominant in Israel at the time, was identified in 85% of the samples tested. Of all workers, 74% had a high viral load (cycle threshold [Ct] value less than 30) at some point in their illness, suggesting contagiousness. No secondary infections were identified, which the researchers said suggests that the infected workers were less contagious than their unvaccinated peers.
Unvaccinated people only source of infection
Workers had lower neutralizing antibody levels during the week before diagnosis (peri-infection period) than matched controls (case-control ratio, 0.361). Higher antibody levels were associated with lower infectivity (higher cycle cutoff values).
“Among fully vaccinated health workers, the onset of breakthrough SARS-CoV-2 infections was correlated with neutralizing antibody titers during the peri-infection period,” the authors wrote.
The likely source of COVID-19 infection among the 37 health workers for which data is available was an unvaccinated person, who was a member of the household in 57% of cases. In 30% of cases, the suspected source was a colleague or an unvaccinated patient, of which 7 of 11 were linked to a single hospital outbreak involving an unvaccinated index patient who had received non-invasive positive pressure ventilation before being diagnosed as having the alpha Variant.
Of the total cohort, 46% were nurses, 26% worked in administration or maintenance, 15% were allied health professionals, and 13% were physicians. The average age was 42, 64% were female, and only one person was immunocompromised. The median interval between the second vaccine dose and the diagnosis of COVID-19 was 39 days.
The authors said the results are important in predicting how the expected decrease in SARS-CoV-2 antibody levels after vaccination will affect the clinical outcome of COVID-19, whether a booster dose will be required and whether people vaccinated are protected. “Such predictive ability is particularly important for the development of new vaccines,” they wrote.
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