Researcher analyzed COVID-19 testing data among hospital staff at University of California Irvine Health in Orange County.
They found that positive cases among the workers had a steep drop off once they started getting the second shot of either the Pfizer-BioNTech or Moderna vaccine.
After three weeks, the rate of positive cases had fallen by 94 percent.
COVID cases dramatically dropped in the weeks after the second dose became available to UCI hospital employees
Test positivity rate dropped to zero in the weeks following the second dose’s availability
For the study, published in JAMA Network Open, the team gathered data from November 2020 to March 2021.
At the hospital, employees were tested if they reported symptoms of COVID-19, and there was also randomly administered asymptomatic testing performed every week.
From November into early January, the trend of cases detected among employees followed county-wide trends.
While the county recorded 2,000 cases per day in late November to 4,000 per day in late December, the hospital saw about 10 per day in November and 18 in December.
The second dose became available to staff in the first week of January and, a week later, cases in the hospital began to diverge from the county.
After one week, daily cases in the hospital fell from 18 per day to eight, marking a 55 percent drop.
Daily cases fell to three after two weeks, an 85 percent decrease, and all the way down to one new case a day after three weeks, which is a reduction of 94 percent.
Case rates remained at that level through March.
During this period, county-wide cases were falling as well, as the vaccine was first beginning to make impact in the local community.
County-wide cases were not falling anywhere near as quickly as those among hospital employees, though.
‘These findings are consistent with past experience with other viral respiratory infections, such as influenza and measles, in which vaccination reduces overall infection rates, viral shedding, and both symptomatic and asymptomatic transmission,’ the authors wrote.
The researchers findings are consistent with nationwide trends.
As more people in America have gotten vaccinated, cases have begun to drop.
According to data from the Centers for Disease Control and Prevention, 67.2 percent of American adults, and 55.1 percent of all Americans, have received at least one shot of a COVID-19 vaccine.
More than 150 million Americans, or 47 percent of the population, are fully vaccinated.
Vaccine demand was at its highest in April, where 45 million Americans got at least their first dose of the vaccine in one month.
Daily cases across the country have fallen by nearly 80 percent since April 15, from 70,000 a day on average to around 15,000 a day.
There are some fears that cases will soon be trending in the wrong direction again, though.
With the Indian ‘Delta’ variant – a more contagious virus strain of COVID – now taking over as the dominant strain in the U.S., some fear cases my rise once again among the unvaccinated.
There is also data from Israel that shows the Pfizer vaccine, which is the most common one in America, may only have 64 percent efficacy against the strain.