A positive COVID-19 test has a bit of hope: you'll be immune to the coronavirus for at least a few months.
But a new research, titled "Sars-Cov-2 Seropositivity and Subsequent Infection Risk in Healthy Young Adults: A Prospective Cohort Study," claimed that immunity from reinfection is not guaranteed.
A nurse prepares an injection with a dose of the AstraZeneca vaccine.
COVID-19 can be contracted twice, according to an observational analysis of over 3,000 stable US Marine recruits. Still, those who have had it previously have a lower risk of infection.
During a six-week observation period, about 10% of recruits who had previously been infected with COVID-19 were reinfected. Recruits who had never been contaminated before tested positive 50% of the time during the study.
The study authors believe that the cramped living conditions on the military bases where the findings took place led to a higher overall infection rate. The risk of reinfection extends to all young people.
Antibodies Provide Some Protection?
Around 189 of the recruits - mainly young men between the ages of 18 and 20 - were seropositive. It means that they had been infected with the coronavirus and had antibodies in their blood.
Most people have an antibody response to infection. The immune system creates proteins to combat particular intruders if they return. While antibodies can wane in the months following infection, the immune system has other defenses in place.
Commander Andrew Letizia, an infectious disease physician and the study's lead researcher said the team measured antibodies as evidence of prior infection.
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However, he did claim that some recruits had previously tested positive but no longer had detectable antibodies at the analysis time. Hence, the 10% reinfection rate could be understated.
Those that had previously been sick and had not been reinfected had lower antibody levels than those who had previously been sick but had not been reinfected.
Professor Stuart Sealfon of the Icahn School of Medicine at Mount Sinai in New York, and senior author of the US Marine Corps report, underscored that those young people will catch the virus again and still spread it to others despite being previously infected.
"Immunity is not guaranteed by past infection, and vaccinations that provide additional protection are still needed for those who have had COVID-19," Prof Sealfon told the PA news agency per The Independent.
Reinfection Is About One-Fifth as Likely as a New Infection?
The authors concluded that young people who have antibodies are about five times less likely to become infected than those who do not have antibodies, based on a study of Marine recruits. Similar findings have been found in other populations.
A preprint analysis of British healthcare staff, titled "Do Antibody Positive Healthcare Workers Have Lower Sars-Cov-2 Infection Rates Than Antibody Negative Healthcare Workers? Large Multi-Centre Prospective Cohort Study (the Siren Study), England: June to November 2020," showed that those who had not previously been infected with COVID-19 had a five-fold higher risk of infection than those who had previously been infected.
COVID-19 infection gave people under the age of 65 about 80% protective immunity after six months, according to a Danish study of 4 million people. The study, titled "Assessment of Protection Against Reinfection With Sars-Cov-2 Among 4 Million Pcr-Tested Individuals in Denmark in 2020: A Population-Level Observational Study," said that only 47% of the elderly were covered from reinfection.
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