New Study Sheds Light on COVID-19 Reinfection Rates

A surprising number of people who test positive for COVID-19 can be reinfected. A new study published in The Lancet revealed, in Denmark, as many as one in five young and middle-aged Danes who were exposed to COVID-19 twice were reinfected.

Denmark has an extensive and inclusive healthcare system and employed an aggressive, free-of-charge PCR COVID-19 testing strategy in 2020 that included approximately 4 million individuals, or about 69% of the population.

According to Fast Company, the study found just 0.65% who tested positive for COVID-19 in the spring were reinfected later in the year. But since only 2% of the total population were infected with the virus, a surprising number did become reinfected.

People over the age of 65 had only 47% protection against reinfection, said the study authors.

"Natural protection, especially among older people, cannot be relied on," they wrote, calling for continued social distancing and vaccination for that population. The scientists found natural protection continued for at least six months.

However, experts point out the study did not say if variants of SARS-CoV-2 could be responsible for the rash of reinfections or if the study participants had any symptoms of the virus.

According to Kaiser Health News, other coronaviruses cause reinfection. The common cold is a case in point. But so far, as of February 2021, fewer than 50 cases of COVID-19 reinfection have been documented by a global reinfection tracker and only 5 cases have been confirmed in America.

A published case study revealed a 25-year-old man in Washoe County, Nevada, suffered two episodes of COVID-19, one in April and the second at the beginning of June 2020. Genetic testing showed the viruses that caused his two bouts of COVID-19 were different, so it was not a case of one prolonged illness. In fact, the second time around he had a worse outcome from the disease.

Researchers said, while infection with SARS-CoV-2, the virus that causes COVID-19, does elicit an immune response, we do not know why some people are still susceptible to reinfection or how long immunity lasts.

According to Mic, our lack of knowledge about the novel coronavirus makes it difficult to predict how the human immune system will respond even if antibodies are present to combat the disease. The Nevada incident was not isolated as another distinct case of reinfection was noted in South America. That person was also reportedly sicker the second time around.

The Centers for Disease Control and Prevention has published guidelines on what constitutes reinfection. According to the CDC, people who develop symptoms of COVID-19 more than 90 days after the initial infection might potentially be reinfected. The agency suggests test specimens from each infection are analyzed to see if the genetic sequencing differs. A variation of genomic sequencing would suggest reinfection and not a continuation of the original illness.