Although the antibodies induced by SARS-CoV-2 infection are largely protective, they do not fully protect against reinfection in young people, as evidenced by a longitudinal prospective study of over 3000 healthy young limbs. from the US Marines Corps conducted by researchers at the Icahn Mount Sinai School of Medicine and Naval Medical Research Center, published April 15 in The Lancet Respiratory Medicine.
“Our results indicate that reinfection with SARS-CoV-2 in healthy young adults is common,” says Stuart Sealfon, MD, Sara B. and Seth M. Glickenhaus professor of neurology at Icahn Mount School of Medicine. Sinai and main author of the paper. “Despite a previous infection with COVID-19, young people can catch the virus again and can still pass it on to others. This is an important point to know and remember as the vaccine rollout continues. Young people should be vaccinated whenever possible, as vaccination is necessary to stimulate immune responses, prevent re-infection and reduce transmission. “
The study, conducted between May and November 2020, found that about 10% (19 of 189) of participants previously infected with SARS-CoV-s (seropositive) were re-infected, compared with new infections in 50% (1,079 out of 2,247) of participants who had not been previously infected (HIV negative). While HIV-negative study participants had a five-fold higher risk of infection than HIV-positive participants, the study showed that HIV-positive people are still at risk of re-infection.
The study population consisted of 3,249 marine recruits aged 18 to 20, predominantly male, who, upon arrival in a two-week quarantine area supervised by the Navy before beginning basic training, were assessed. for baseline SARS-CoV-2 IgG seropositivity (definition as a dilution of 1: 150 or greater on the receptor binding domain and immunosorbent bound to a full spike protein enzyme [ELISA] The presence of SARS-CoV-2 was assessed by PCR at the start, middle and end of quarantine. After appropriate exclusions, including participants with a positive PCR during quarantine, the study team performed three PCR tests every two weeks in the HIV negative and HIV positive groups after recruits left quarantine and entered basic training.
Recruits who tested positive for a new second COVID-19 infection during the study were isolated and the study team followed up with additional testing. Neutralizing antibody levels were also taken from seropositive participants subsequently infected and selected seropositive who were not re-infected during the study period.
Of the 2,346 Marines followed long enough for this analysis of the reinfection rate, 189 were HIV positive and 2,247 were HIV negative at the start of the study. In both groups of recruits, there were 1,098 (45%) new infections during the study. Of the HIV-positive participants, 19 (10%) tested positive for a second infection during the study. Of the HIV negative recruits, 1,079 (48%) were infected during the study.
To understand why these re-infections occurred, the authors studied the antibody responses of re-infected and uninfected participants. They found that among the HIV-positive group, participants who had been re-infected had lower levels of antibodies to the SARS-CoV-2 virus than those who had not been re-infected. In addition, in the seropositive group, neutralizing antibodies were less frequent (neutralizing antibodies were detected in 45 (83%) of 54 uninfected and in six (32%) of 19 reinfected participants during the six weeks of observation. ).
By comparing new infections between seropositive and seronegative participants, the authors found that the viral load (the amount of SARS-CoV-2 virus measurable) in re-infected seropositive recruits was on average only 10 times lower than in HIV-negative participants infected, which could mean that some were re-infected. individuals might still have the ability to transmit infection. The authors note that this will require further investigation.
In the study, most new cases of COVID-19 were asymptomatic – 84% (16 of 19 participants) in the HIV-positive group vs. 68% (732 of 1079 participants) in the HIV-negative group – or had mild symptoms and none was not. hospitalized.
The authors note some limitations to their study, including the fact that it likely underestimates the risk of re-infection in previously infected people, as it ignores people with very amorous antibody levels following their infection. past. They strongly suggest that even young people who have already been infected with SARS-CoV-2 are a target for vaccination as efforts must be made to prevent transmission and prevent infection in this group.
This work was supported by the Defense Health Agency through the Naval Medical Research Center and the Defense Advanced Research Projects Agency.