A new research study led by researchers of The Mount Sinai School of Medicine suggests that vaccination against COVID-19 remains crucial even in young adults who were previously infected.
The findings were published in the journal The Lancet Respiratory Medicine.
Stuart Sealfon, MD, the Sara B. and Seth M. Glickenhaus Professor of Neurology at the Icahn School of Medicine at Mount Sinai and senior author of the paper said, “Our findings indicate that reinfection by SARS-CoV-2 in healthy young adults is common.”
“Despite a prior COVID-19 infection, young people can catch the virus again and may still transmit it to others. This is an important point to know and remember as vaccine rollouts continue. Young people should get the vaccine whenever possible since vaccination is necessary to boost immune responses, prevent reinfection, and reduce transmission.”
It is reported that although the antibodies induced by SARS-CoV-2 infection are largely protective but they do not completely protect young people against reinfection. And this report is based on the evidence through a longitudinal, prospective study of more than 3,000 young, healthy members of the US Marines Corps conducted by researchers at the Icahn School of Medicine at Mount Sinai and the Naval Medical Research Center.
Between May and November 2020, the study was conducted which revealed that around 10 percent (19 out of 189) of participants who were previously infected with SARS-CoV-s (seropositive) became reinfected, compared with new infections in 50 percent (1.079 out of 2,247) of participants who had not been previously infected (seronegative).
The study showed that seropositive people are still at risk of reinfection, whereas seronegative study participants had a five times greater risk of infection than seropositive participants.
Moreover, the study consisted of around 3,249 predominantly male and 18-20-year-old Marine recruits who, upon arrival at a Marine-supervised two-week quarantine prior to entering basic training, were assessed for baseline SARS-CoV-2 IgG seropositivity.
The presence of SARS-CoV-2 was assessed by PCR at the beginning, middle, and end of quarantine.
After appropriate segregations, including participants with a positive PCR during quarantine, the study team performed three bi-weekly PCR tests in both seronegative and seropositive groups once recruits left quarantine and entered basic training.
The study team followed up with additional testing for the recruits who tested positive for a new second COVID-19 infection during the study were isolated. Levels of neutralising antibodies were also taken from subsequently infected seropositive and selected seropositive participants who were not reinfected during the study period.
At the beginning of the study out of 2,346 Marines followed long enough for this analysis of reinfection rate, 189 were seropositive and 2,247 were seronegative.
Across both groups of recruits, there were 1,098 (45 percent new infections during the study. Among the seropositive participants, 19 (10 percent tested positive for a second infection during the study. Of the recruits who were seronegative, 1,079 (48 percent) became infected during the study.
The authors studied the reinfected and not infected participants’ antibody responses to understand why these reinfections occurred. When they found that among the seropositive group, participants who became reinfected had lower antibody levels against the SARS-CoV-2 virus than those who did not become reinfected.
In addition to that neutralizing antibodies were less common (neutralizing antibodies were detected in 45 (83 percent) of 54 uninfected in the seropositive group, and in six (32 per cent) of 19 reinfected participants during the six weeks of observation).
Comparing new infections between seropositive and seronegative participants, the authors found that viral load (the amount of measurable SARS-CoV-2 virus) in reinfected seropositive recruits was on average only 10 times lower than in infected seronegative participants, which could mean that some reinfected individuals could still have a capacity to transmit infection.