People who have recovered from a COVID-19 infection are likely to be protected from reinfection for at least six months, but according to a study published Wednesday, this protection drops dramatically for people over the age of 65.
The study, published in The Lancet, found that the protection of the general population is 80% or higher for those under 65, but about 47% for those aged 65 and over, which means they are more likely to be infected again.
The study found that among people under the age of 65 who had COVID-19 during the first wave, between March and May 2020, only 72 of more than 11,000 tested positive again during the second wave. from September to December 2020.
The rate of infection during the second wave was five times higher for people who gave negative results during the first wave.
For people over the age of 65, the numbers were slightly higher, with 17 of 1,931 gave positive results twice. The study found that 2% of people over the age of 65 who tested negative in the first wave were subsequently tested positive during the second wave.
The authors found no evidence that protection against repeated infection decreased after six months of follow-up, but because COVID-19 was only discovered in December 2019, they said long-term studies were needed.
However, the study concluded that it cannot depend on natural protection – especially among the elderly – and vaccination of all populations is the most reliable to ensure protection against COVID-19.
The authors said that these results highlight the importance of measures to protect the elderly during the pandemic, such as increased physical distance and their prioritization for vaccines, even for those who have recovered from the virus.
Centers for Disease Control and Prevention recommend vaccinating people who have previously been infected with COVID, as there is no clear evidence of how long natural immunity lasts.
Several studies have found that COVID-19 vaccines have much higher levels of neutralizing antibodies than is present with natural infection, providing vaccinated individuals with a much more durable and high-quality level of protection.
The Lancet study analyzed data on patients collected in Denmark, as the county has established a successful national testing program. The country has expanded its free PCR testing program, and by December 31, more than 10 million PCR tests had been performed on 4 million people, representing more than two-thirds of the country’s population.
Recent studies have suggested that reinfections are rare and that immunity may last for at least six months, but the Lancet study was the first to examine the question on such a large scale.
The study was conducted before the appearance of more contagious variants, and the authors said they also could not determine whether the severity of symptoms played a role in protecting the reinfection.