July 23 (UPI) -- Vaccinating fewer than half of the teachers at a large urban school district led to a 95% reduction in COVID-19 test positivity rates among staff members when they returned for in-person classes, according to data released Friday by the Centers for Disease Control and Prevention.
A vaccination initiative in Philadelphia to inoculate the city's 22,808 public school teachers between Feb. 23 and April 3 resulted in 46% becoming fully vaccinated, the data showed.
From March 21, when in-person classes resumed, through April 23, fewer than 1% of the more than 34,000 virus tests performed on the teachers were positive.
Test positivity rates were less than 0.1% among teachers who were fully vaccinated, compared with 1.2% for those who had received one-dose of the shot and nearly 2% for those who were unvaccinated, according to the CDC.
These results occurred when the Philadelphia's daily COVID-19 incidence was between 29 and 33 cases per 100,000 people in the general population.
"During a period of relatively high community transmission, weekly ... testing of school staff members in the School District of Philadelphia, one of the country's largest public school districts, revealed significantly fewer infections among vaccinated school staff members compared with those who were unvaccinated," the agency researchers wrote.
"Efforts to promote COVID-19 vaccination among school staff members before the upcoming 2021-22 school year will be foundational to ensure a safe learning environment," they said.
Teachers were considered fully vaccinated if they received both doses of the two-shot COVID-19 vaccine from Pfizer-BioNTech, according to the agency.
The vaccination program was coordinated by the city public health department and Children's Hospital of Philadelphia and offered to all of city's public school teachers, the agency said.
"Current CDC recommendations indicate that fully vaccinated persons with no known exposure to COVID-19 and no COVID-19-compatible symptoms can be exempted from routine testing programs," the CDC researchers wrote.
"Therefore, schools with high rates of staff member vaccination coverage might be able to implement in-person learning without the need for routine testing programs," they said.