Study shows past COVID-19 infection doesn’t fully protect young people against reinfection COVID-19感染不能完全保護年輕人免受再次感染

Editor’s note: If a natural covid 19 infection could not generate sufficient amounts of antibodies to neutralize the future viral antigens, what else could we do?

So this study may provide some support for an infected person to get vaccinated to strengthen his immunity. The problem is, vaccines cannot provide all immunity that is needed to fight covid 19. Vaccinated people are still at risk of getting infected with the virus.

Remember that it is more important to defeat the virus after you are infected than prevent yourselves from getting it. This is so because sooner or later you may get the covid 19 virus. If the virus cannot do much harm to you, why you should care? Fortunately, there are many things we can do to mitigate the damage induced by the covid 19 infection.

編者註:如果自然的covid 19感染不能產生足夠數量的抗體來中和未來的病毒抗原,我們還能做什麼? 因此,本研究可能為感染者接種疫苗以增強其免疫力提供一些支持。

問題是,疫苗無法提供抵抗covid 19所需的全部免疫力。接種疫苗的人仍然有被病毒感染的風險。

請記住,感染病毒後擊敗病毒比阻止自己感染病毒更為重要。 之所以如此,是因為您遲早會感染covid 19病毒。 如果該病毒不能對您造成太大傷害,那麼您為什麼要注意呢? 幸運的是,我們可以做很多事情來減輕covid 19感染引起的損害。

The Mount Sinai Hospital / Mount Sinai School of Medicine

Research News

IMAGE: Stuart Sealfon, MD, Professor of Neurology, Neuroscience, and Pharmacological Sciences, Icahn School of Medicine at Mount Sinai view more  Credit: Mount Sinai Health System

Although antibodies induced by SARS-CoV-2 infection are largely protective, they do not completely protect against reinfection in young people, as evidenced 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, published April 15 in The Lancet Respiratory Medicine.

“Our findings indicate that reinfection by SARS-CoV-2 in health young adults is common” says 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. “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.”

The study, conducted between May and November 2020, 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). While seronegative study participants had a five times greater risk of infection than seropositive participants, the study showed that seropositive people are still at risk of reinfection.

The study population consisted of 3,249 predominantly male, 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 (defined as a 1:150 dilution or greater on receptor binding domain and full-length spike protein enzyme-linked immunosorbent [ELISA] assays.) The presence of SARS-CoV-2 was assessed by PCR at initiation, middle and end of quarantine. After appropriate exclusions, 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.

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. Levels of neutralising antibodies were also taken from subsequently infected seropositive and selected seropositive participants who were not reinfected during the study period.

Of the 2,346 Marines followed long enough for this analysis of reinfection rate, 189 were seropositive and 2,247 were seronegative at the start of the study. Across both groups of recruits, there were 1,098 (45%) new infections during the study. Among the seropositive participants, 19 (10%) tested positive for a second infection during the study. Of the recruits who were seronegative, 1,079 (48%) became infected during the study.

To understand why these reinfections occurred, the authors studied the reinfected and not infected participants’ antibody responses. 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, in the seropositive group, neutralising antibodies were less common (neutralising antibodies were detected in 45 (83%) of 54 uninfected, and in six (32%) 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. The authors note that this will need further investigation.

In the study, most new COVID-19 cases were asymptomatic – 84% (16 out of 19 participants) in the seropositive group vs 68% (732 out of 1,079 participants) in the seronegative group – or had mild symptoms and none were hospitalised.

The authors note some limitations to their study, including that it likely underestimates the risk of reinfection in previously infected individuals because it does not account for people with very love antibody levels following their past infection. They strongly suggest that even young people with previous SARS-CoV-2 infection be a target of vaccination since efforts must be made to prevent transmission and prevent infection amongst this group.


This work was supported by the Defense Health Agency through the Naval Medical Research Center and the Defense Advanced Research Projects Agency.

About the Mount Sinai Health System

The Mount Sinai Health System is New York City’s largest academic medical system, encompassing eight hospitals, a leading medical school, and a vast network of ambulatory practices throughout the greater New York region. Mount Sinai is a national and international source of unrivaled education, translational research and discovery, and collaborative clinical leadership ensuring that we deliver the highest quality care–from prevention to treatment of the most serious and complex human diseases. The Health System includes more than 7,200 physicians and features a robust and continually expanding network of multispecialty services, including more than 400 ambulatory practice locations throughout the five boroughs of New York City, Westchester, and Long Island. The Mount Sinai Hospital is ranked No. 14 on U.S. News & World Report’s “Honor Roll” of the Top 20 Best Hospitals in the country and the Icahn School of Medicine as one of the Top 20 Best Medical Schools in country. Mount Sinai Health System hospitals are consistently ranked regionally by specialty and our physicians in the top 1% of all physicians nationally by U.S. News & World Report.

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