A past COVID-19 infection was associated with an 84 percent lower risk of reinfection among more than 25,000 healthcare workers in the U.K., according to a study published April 9 in The Lancet.
The study, led by researchers at Public Health England, enrolled 25,661 public hospital employees from June 18 to Dec. 31, 2020. Study participants were tested for COVID-19 every two to four weeks for about seven months. They also underwent antibody testing upon their enrollment and after every four weeks.
About 32.3 percent of study participants had either had antibodies at enrollment or had a previous positive COVID-19 or antibody test. The remaining 67.7 percent did not have antibodies or previously test positive for COVID-19.
Of the 8,278 employees who had a previous COVID-19 infection, researchers found 1.9 percent were likely reinfected between June 18, 2020, and Jan. 11, 2021. In contrast, 9.8 percent of the 17,383 employees who hadn't been previously infected contracted the virus during the study period.
The incidence density for the previously infected group was 7.6 new infections per 100,000 person-days, compared to 57.3 per 100,000 for the group that was not previously infected.
"Using a COVID-19 symptomatic case definition aligned with positive PCR results, previous infection reduced the incidence of infection by at least 90 percent and even when we included all possible and probable reinfections reduced the incidence of reinfection by at least 84 percent," researchers said.
They noted that most reinfections involving healthcare workers have not been confirmed and are still undergoing further serological investigation. This process has been hindered by scarce data and a lack of samples from previous infections, they said.
To view the full study, click here.
More articles on public health:
Fully vaccinated but COVID-19 positive? 4 notes on breakthrough case prevalence
1 in 4 American adults don't want a COVID-19 vaccine: NPR
COVID-19 death rates by state: April 12