Most people who have contracted the coronavirus are protected against re-infection for at least six months, according to a new study published by Danish researchers in the Lancet medical journal. That immunity, however, diminishes significantly with age.
The study’s authors said that the research underscores the importance of vaccinating elderly populations but also previously infected individuals as the pandemic wears on.
Researchers analyzed data from Denmark’s national testing and surveillance program, under which nearly 70 percent of the population was tested for the coronavirus last year. They found that natural infection reduced the chances of getting the virus again by about 80 percent in people younger than 65 — and that there was no evidence of that protection weakening over a six-month period.
In those older than 65, a first bout with the virus offered just 47 percent protection against repeat infection. The study did not look at the chances of re-infection from new virus variants, including those first identified in Brazil, Britain and South Africa.
In a commentary published alongside the study, two British immunologists at the Imperial College London called the results “concerning” and emphasized the necessity of ramping up vaccination programs.
“The quality, quantity, and durability of protective immunity elicited by natural infection with SARS-CoV-2 are poor relative to the much higher levels of virus-neutralizing antibodies and T cells induced by the vaccines currently being administered globally,” Rosemary Boyton and Danny Altmann wrote. “The hope of protective immunity through natural infections might not be within our reach, and a global vaccination program with high efficacy vaccines is the enduring solution.”