COVID-19 News: U.S.Naval Study Warns That Young COVID-19 Survivors Despite Having Antibodies Can Still Get Easily Reinfected!
: A new study by the U.S. Naval Medical Research Center and Icahn School of Medicine at Mount Sinai in New York City warns that young COVID-19 survivors despite having antibodies can still easily get reinfected.
The study findings found that seropositive young adults had about one-fifth the risk of subsequent infection compared with seronegative individuals.
The researchers warn that although antibodies induced by initial infection are largely protective, they do not guarantee effective SARS-CoV-2 neutralization activity or immunity against subsequent infection.
The risk of SARS-CoV-2 subsequent infection among seropositive young adults was studied prospectively by the team.
The finding stems from tracking these 3,249 young U.S. Marine recruits between May and October 2020. The research participants comprised predominantly male, 18-20-year-old Marine recruits. Upon arrival at a Marine-supervised two-week quarantine, participants were assessed for baseline SARS-CoV-2 IgG seropositivity, defined as a 1:150 dilution or greater on receptor binding domain and full-length spike protein enzyme-linked immunosorbent (ELISA) assays. SARS-CoV-2 infection was assessed by PCR at initiation, middle and end of the quarantine. After appropriate exclusions, including participants with a positive PCR during quarantine, we performed three biweekly PCR tests in both seropositive and in seronegative groups once recruits left quarantine and entered basic training and baseline neutralizing antibody titers on all subsequently infected seropositive and selected seropositive uninfected participants.
The study found that
among 189 seropositive participants, 19 (10.1%) had at least one positive PCR test for SARS-CoV-2 during the six-week follow-up (1.1 cases per person-year).
In contrast, 1,079 (48.0%) of the 2,247 seronegative participants tested positive (6.2 cases per person-year). The incidence rate ratio was 0.18 (95% CI 0.11-0.28, p<0.00001). Among seropositive recruits, infection was associated with lower baseline full-length spike protein IgG titers (p<0.0001). Compared with seronegative recruits, seropositive recruits had about 10-fold lower viral loads (ORF1ab gene, p<0.005), and trended towards shorter duration of PCR positivity (p=0.18) and more frequent asymptomatic infections (p=0.13).
Among seropositive participants, baseline neutralizing titers were detected in 45 of 54 (83.3%) uninfected and in 6 of 19 (31.6%) infected participants during the 6 weeks of observation (ID50 difference p<.0001).
From the study findings, 189 had previously tested positive for the SAR-CoV-2 virus. During the six-week study itself, 10% of those who had tested positive got reinfected.
The study findings were published on a preprint server and have yet to be peer reviewed. https://www.medrxiv.org/content/10.1101/2021.01.26.21250535v1
The study shows that having being infected with the virus that causes COVID-19 is not a foolproof shield against reinfection
Study author told Thailand Medical News, "You don't have a get-out-of-jail-free card just because you have antibodies from a previous infection."
Dr Sealfon is a professor of neurology at Icahn School of Medicine at Mount Sinai in New York City.
The study participants were beginning basic training and were initially held in Navy quarantine for two weeks, after two weeks of at-home quarantine, according to the study. Once training began, recruits were tested for COVID-19 every two weeks over a six-week period.
The study results showed that 19 of the 189 recruits who already had COVID tested positive for a second infection during the research.
The study team said that the first- and second- infections involved the same strain of the SARS-CoV-2 virus and none involved the new, more transmissible U.K., South African or Brazilian strains that have raised alarm in recent weeks.
It was found that of 2,247 recruits who had not previously had COVID, 1,079 (48%) became infected during the study.
Importantly that means recruits with a prior COVID infection "had about a fifth the risk for getting infected again when in basic training, compared with Marines who had not been previously infected and didn't have antibodies," Dr Sealfon said.
It was found that all those who tested positive during the study had "mild" symptoms. None were hospitalized. But symptom risk and length of infection were the same, regardless of prior COVID history.
Dr Sealfon added, "The only difference was that the amount of virus on our swab tests was a little bit lower in the Marines with antibodies from a prior infection.”
It was observed that reinfected Marines also had lower levels of antibodies from their initial bout, compared with Marines who didn't get reinfected.
Dr Sealfon further added, "Two-thirds of the 19 Marines who were reinfected didn't have measurable neutralizing antibodies, suggesting that some people who get infected don't generate antibodies.”
Hence the study found that having antibodies after infection does protect you against reinfection but even if you've had COVID, there remains a risk you'll get it again.
Dr Sealfon commented, "That might not cause problems for the patient, and certainly young people like those in our study are mostly asymptomatic. But it certainly can mean that there is a risk that they can then transmit a new infection to those who are more vulnerable."
The study finds that mask-wearing, social distancing and getting vaccinated will still be important, regardless of your prior infection history.
Dr Sealfon said, “Vaccination to provide additional protection is still warranted for those who've been infected, because we know that you certainly boost your antibody response with vaccination, even if you already have antibodies."
However Dr Sandro Cinti, a professor of infectious disease at Michigan Medicine at the University of Michigan in Ann Arbor, said it's best not to read too much into these findings.
Dr Cinti warned, "These are early results, with a very small number of patients. You have to be very careful interpreting all the COVID studies that are coming out now, many of which have not been peer-reviewed."
Dr Cinti said a viral infection typically does provide protection from further infection.
He said, "Is there the possibility of reinfection with COVID? Maybe. But none of these studies answer that question anywhere near definitively. The only thing definitive is that we just don't really know."
Dr Cinti said that the U.S. Centers for Disease Control recommends everyone 18 and older get vaccinated whether or not they have had COVID,
Dr Cinti added, "It makes sense because we know the protection rate with vaccination is about 95%, and we don't know what the protection rate is for COVID patients. I suspect it's also that high, but we don't know that. If the goal is to reach herd immunity, you probably want to aim at getting everyone vaccinated."
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