According to a new study, young people who have previously been infected with coronavirus will not be fully protected against reinfection.
Researchers at Mount Sinai Icahn School of Medicine analyzed data on more than 3,000 healthy U.S. Marine Corps members aged 18 to 20 years.
They found that approximately 10% of those involved in the study who had previously been infected with Covid-19 had been reinfected.
The study authors warned that despite previous infection and the presence of antibodies, vaccination is still needed to boost immune responses, prevent reinfection, and reduce transmission.
They added that young people should get the vaccine whenever possible.
According to a new study, young people who have previously been infected with coronavirus will not be fully protected against reinfection
According to the observational study conducted between May and November 2020, 19 of 189 Covid-infected marines recaptured the virus.
It was compared with new infections in 50% (1,079 of 2,247) of participants who had not previously been infected with the virus.
Although the study was conducted on fit, mostly male recruits, the researchers believe the risk of reinfection will apply to many young people.
However, the exact reinfection rates will not be applicable in other environments, due to overcrowded living conditions on a military base.
The team said the close personal contact needed for basic training will likely contribute to a higher overall infection rate than anywhere else.
For example, a study of four million people in Denmark found that the risk of infection was five times higher in people who had not had the disease before.
But the researchers found that only 0.65% of those who had had Covid-19 during the first wave in Denmark tested positive again during the second wave, compared with 3.3% of people who tested positive. after being initially negative.
In addition, a prepress study that included British healthcare workers found that those who had not been previously infected were five times more likely to become infected than people who had a past infection.
Professor Stuart Sealfon, lead author of the study, said it is important to remember that despite a previous infection, young people can catch the virus again.
“Immunity is not guaranteed by past infection and vaccines that provide additional protection are still needed for those who have had Covid-19.”
Recruits who tested positive for a second infection during the study were isolated and the researchers did additional testing.
Neutralizing antibody levels of subsequently infected participants that were not reinfected during the study period were also taken.
Of the 2,346 participants followed long enough to do this analysis, 189 were seropositive and 2,247 were seronegative at the start of the study.
In both groups, there were 1,098 (45%) new infections during the study and of the seronegative recruits, 1,079 (48%) became infected.
The authors studied the antibody responses of reinfected and uninfected participants to understand why these reinfections occurred.
They found that, among the HIV-positive group, participants who were reinfected had lower levels of antibodies against the virus than those who did not.
When they compared new infections, they found that patients who had the virus before and were reinfected had about ten times less of the virus in their system than someone who became infected for the first time.
This suggests that some reinfected individuals may still be able to transmit the virus, but the authors noted that more research will be needed.
They found that approximately 10% of those involved in the study who had previously been infected with Covid-19 had been re-infected.
In the study, most new cases were asymptomatic: 84% (16 of 19 participants) in the HIV-positive group and 68% (732 of 1,079) in the seronegative group, or had mild symptoms, and none were admitted. to the hospital.
The authors noted some limitations of the study, including that it is likely to have underestimated the risk of reinfection in previously infected individuals.
This is because it does not take into account people with very low antibody levels after their last infection.
They were also unable to determine how HIV-positive recruits recruited the previous infection and confirmed it by the PCR test or determine the severity and symptoms they presented.
They found that, among the HIV-positive group, participants who were reinfected had lower levels of antibodies to the virus than those who did not.
The researchers said they may also have missed detectable infections that occurred between PCR tests every two weeks during the study, published in the journal The Lancet Respiratory Medicine.
“Although antibodies induced by the initial infection are largely protective, they do not guarantee effective SARS-CoV-2 neutralizing activity or immunity to subsequent infection,” the study mentioned.
A separate study published in the journal Lancet in March found that most people who have had COVID-19 are protected from re-inducing it for at least six months, but older people are more prone to reinfection than people teens.