Protection from reinfection lasts at least 5 months
People who have already contracted Covid-19 gain significant protection from reinfection for at least 5 months, according to a recent study by Public Health England (PHE).
The study was conducted on two matched groups of volunteers – 6,000 who had already been infected and 14,000 who had not – from June to November last year, reports the Financial Times.
Preliminary results of the study released on Thursday found those who had previously contracted Covid-19 had 83% protection from reinfection and 94% protection from symptomatic Covid-19 – similar results to the recent vaccine trials.
Susan Hopkins, PHE senior medical adviser, described results as “strongly encouraging,” although the protection is not complete.
“Natural infection looks as good as a vaccine, which is very good news for the population,” she said.
During the study, 44 people in the previously infected group of 6,000 tested positive at least three months apart, suggesting that they had been “potentially reinfected.” The cases were not considered to be proven reinfections as genomic analysis was not available to confirm whether different viruses were responsible for the different infections.
However, Prof Hopkins still urged caution.
“It is important not to misunderstand these early findings. If you believe you already had the disease and are protected, you can be reassured it is highly unlikely you will develop severe infection but there is still a risk that you could acquire an infection and transmit to others,” she said.
The effectiveness of vaccines was not investigated in the study as they were not approved soon enough to meet the cut-off point of the study. Researchers were also unable to examine chances for reinfection with the new variant of Covid-19.