(Reuters) – Data from health care workers at medical centers in the United States and Israel are confirming the effectiveness of both the Pfizer and Moderna vaccines against COVID-19.
Theas in the New England Journal of Medicine.
Pooled employee data from the University of California, San Diego, and the University of California, Los Angeles, health systems shows that during a system of aggressive testing, conducted during a surge of COVID-19 cases in the general population, the rate of new infections among the staff dropped dramatically, beginning the second week after the first dose was given.
Testing showed new cases among 2.5% of those tested within the first week after the first dose, 1.2% during the second week, 0.7% in the third week, 0.4% during the week after the second dose was given and less than 0.2% in the second week after the second dose.
The absolute risk of testing positive for COVID-19 among the health care workers was higher than what might have been expected from the initial data for the Pfizer and Moderna vaccines, but the workers were being tested regularly and aggressively, and there was a surge of community infections at the time, the researchers said.
The original Pfizer trial did not test asymptomatic volunteers and there was only a single screening of asymptomatic people before the second dose was administered in the Moderna study.
“The rarity of positive test results 14 days after administration of the second dose of vaccine is encouraging and suggests that the efficacy of these vaccines is maintained outside a trial setting,” said the team, led by Jocelyn Keehner, MD, of University of California San Diego Health.
In North Texas, where workers were also vaccinated in the midst of the largest COVID-19 surge the region had seen, 2.61% of unvaccinated employees developed the infection versus 1.82% of partially vaccinated workers and 0.05% of fully vaccinated employees.
The effect on the workforce “has been dramatic,” said the research team led by William Daniel, MD, of the University of Texas Southwestern Medical Center in Dallas.
“We observed a greater than 90% decrease in the number of employees who are either in isolation or quarantine,” they said. “This decrease has preserved the workforce when it was most needed” during the surge.
At Hadassah Hebrew University Medical Center in Jerusalem, in a community with a high incidence of COVID-19 infections, data from vaccinated health care workers shows that the Pfizer vaccine seemed to offer major protection against the U.K. variant of the disease, known as B.1.1.7.
Vaccination “results in a major reduction of new cases of COVID-19 among those who received two doses of the vaccine, even when a surge of the B.1.1.7 variant was noted in up to 80% of cases,” said Shmuel Benenson, MD, of Hadassah Hebrew and colleagues.
“These findings suggest that widespread and effective vaccination among healthcare workers provides a safe environment,” they said, “even in the presences of a high rate of SARS-CoV-2 infection in the community.”
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