Pfizer and BioNTech’s coronavirus reduces the risk of becoming ill with COVID-19 by five to 18 times for fully immunized humans, two new studies show.
In a report, only 0.4 percent of health workers in Israel who received both shots of the COVID-19 vaccination later tested positive compared to 7.2 percent of non-vaccinated workers.
This means that healthcare professionals who received both doses were 18 times less likely to become ill.
Meanwhile, in the second study, 1.8 percent of fully vaccinated frontline staff at a Tennessee hospital contracted the virus compared to 8.5 percent of non-vaccinated workers, putting the latter group at a 4.7-fold greater risk of infection.
The results are in line with the 95% efficacy that Pfizer and BioNTech reported from their late-stage clinical trial in December 2020, which led to emergency approval from the Food and Drug Administration (FDA).
Because vaccinated people were not only less likely to get coronavirus, but even get an asymptomatic infection, the results are also a sign that the vaccine can prevent transmission between close contacts.
At a hospital in Tel Aviv, Israel, 5,517 health workers or 82.2% (light blue line) received two doses between December and February and 757, 11.3% (yellow line) were not vaccinated. Of these, 0.4% of those fully vaccinated later tested positive for Covid compared to 7.2% of non-vaccinated humans
In another study at a Tennessee hospital, 2,776 employees, 53.2%, were fully vaccinated, 2,165 employees, 41.5%, were unvaccinated. Of these, 1.8% of the fully vaccinated later tested positive for Covid (yellow line) compared to 8.5% of the unvaccinated workers (blue line)
For the study, published in the Journal of the American Medical Association (JAMA), the Tel Aviv Sourasky Medical Center team collected data from 6,710 of their staff.
Between December 20, 2020 and February 25, 2021, 5,953 or 88.7 percent received at least one dose and 5,517 or 82.2 percent received two doses.
The remaining 757, 11.3 percent, were not vaccinated.
Workers were considered fully vaccinated when it was seven days or later after receiving their final dose.
Of the fully vaccinated staff, 27 of 5,517 or 0.4 percent later tested positive for the virus, as did 55 of 757 or 7.2 percent of the unvaccinated staff.
In the Israel study, only 8 fully vaccinated individuals (solid blue line) were symptomatic and 19 were asymptomatic (dotted blue line) compared with 38 symptomatic non-vaccinated workers (solid yellow line) and 17 asymptomatic workers (dotted yellow line)
Researchers also compared the number of symptomatic and asymptomatic diseases.
Eight of the fully vaccinated people who tested positive had symptoms such as cough, fever and shortness of breath compared to 38 of the non-vaccinated workers.
The team says this shows that the vaccine is not only effective in blocking disease, but if a person becomes ill, it is very unlikely that they will experience symptoms.
They determined that Pfizer’s shots were 97 percent effective in preventing symptomatic disease and 86 percent effective in preventing asymptomatic infection.
In this retrospective cohort study of regularly screened healthcare professionals, 2 doses of [Pfizer] vaccine was associated with significantly lower incidence of both symptomatic and asymptomatic SARS-CoV-2 infection, ‘the authors wrote.
In the Tennessee study, 56.9% of fully vaccinated people were asymptomatic (left, yellow line) and 43.1% were symptomatic (right, yellow line) compared with 42.7% of non-immunized workers who were asymptomatic ( left, blue line) and 57.3%, as before symptomatic (right, blue line)
For the second study, which was also published in JAMA, the team from St Jude Children’s Research Hospital, Memphis, Tennessee, looked at data from 5,217 employees.
Between December 17, 2020 and March 20, 2021, 3,052, 58.5 percent received at least one dose, and 2,776 or 53.2 percent received both doses.
The remaining 2,165 employees or 41.5 percent were unvaccinated.
Nasal swab specimens showed that at least 1.8 percent – 51 out of 2,776 – tested positive at least 10 days after the second dose compared to 8.5 percent – 185 out of 2,165 people.
Similar to the first study, the majority of fully vaccinated people were asymptomatic with 56.9 percent compared to 42.7 percent of non-immunized workers.
‘Unvaccinated workers had higher cumulative incidence of a positive test result than vaccinated workers and higher incidences of positive test results via asymptomatic screening for symptoms or for known exposure,’ the authors wrote.