Past COVID-19 infections do not completely protect young people from reinfection

Past COVID-19 infections cannot completely prevent reinfection in adolescents. Observational studies of more than 3,000 healthy members of the US Marine Corps showed that most were between the ages of 18 and 20. Lancet Respiratory Medicine journal.

The authors state that despite previous infections and the presence of antibodies, vaccination is still needed to boost the immune response, prevent reinfection, and reduce infection. Young people You should be vaccinated as much as possible.

In this study, between May and November 2020, approximately 10% (19 of 189) of participants previously infected with SARS-CoV-2 (seropositive) were re-infected, but 50 % (1,079 out of 2,247) were newly infected. Percentage of participants who have never been infected (seronegative).

Although the study was young and healthy, mostly male Marines, the authors believe that the risk of reinfection found in their study applies to many young people, but the exact rate of reinfection is elsewhere. Living conditions at military bases and close personal contact required for basic training (because of congestion), which may not be the case in places, contribute to higher overall infection rates than found elsewhere. There is likely to be). For example, a survey of 4 million people in Denmark found that people who had never been infected with COVID-19 were five times more likely to be infected, but those who were the first to be infected with COVID-19 in Denmark. It was only 0.65%. The wave showed positive again during the second wave, compared to 3.3% of those who showed positive after the first negative. In addition, a preprint study involving UK healthcare workers found that people who had never been infected before were five times more likely to be re-infected than those who were infected in the past.

Professor Stuart Sirphon of Mount Sinai School of Medicine in the United States said: “As vaccine deployment continues to gain momentum, despite previous COVID-19 infections, young people can catch the virus again and still infect others. Past infections can cause it. Immunity is not guaranteed and people infected with COVID-19 still need vaccination to provide additional protection. “

In this study, U.S. Marine Corps recruits entered a monitored quarantine facility for another two weeks after completing unsupervised quarantine at home for two weeks. They underwent antibody testing to see if any of the recruits were seropositive (they were previously infected with SARS-CoV-2 and had antibodies). We also tested for new SARS-CoV-2 infections at baseline, weeks 1 and 2 of quarantine, and completed a questionnaire that included demographics, risk factors, medical history, and COVID-19 symptoms. Participants were excluded from the study if the PCR test was positive for COVID-19 during supervised quarantine. After quarantine, new employees who are not infected with COVID-19 participate in basic training, are tested for new SARS-CoV-2 infection by PCR test every 2 weeks for 6 weeks, and follow-up questions on COVID-19 symptoms. I answered the vote.

During the study, new recruits who were positive for a second COVID-19 infection were quarantined and the research team conducted additional tests. Neutralizing antibody levels were also obtained from subsequently infected sero-positive and selected sero-positive participants who were not re-infected during the study period.

Of the 2,346 Marines followed for sufficient time to analyze this reinfection rate, 189 were seropositive and 2,247 were seronegative at the start of the study. There were 1,098 (45%) new infections during the study across both groups of new employees. Of the seropositive participants, 19 (10%) were positive for a second infection during the study. Of the recruits who were negative for serologic reactions, 1,079 (48%) were infected during the study.

To understand why these reinfections occurred, the authors studied the antibody response between reinfected and uninfected participants. They found that in the seropositive group, reinfected participants had lower antibody levels against the SARS-CoV-2 virus than non-reinfected participants. In addition, neutralizing antibodies were less common in the serum-positive group (neutralizing antibodies were found in 45 (83%) of 54 uninfected individuals and 19 re-infections during the 6-week observation. Detected in 6 (32%) of infected participants).

Comparing the new infections between sero-positive and sero-negative participants, the authors found that the viral load of re-infected sero-positive recruits (measurable amount of SARS-CoV-2 virus) was We found that on average, it was only 10-fold lower than infected serum-negative participants. This can mean some reinfection. Individuals may still have the ability to spread the infection, but the authors state that this requires further investigation.

In this study, most new COVID-19 cases were asymptomatic, 84% in the seropositive group (16 out of 19 participants) and 68% in the seronegative group (out of 1,079 participants). 732 people). ..

Lieutenant Dawnweir of the US Naval Medical Research Center said: “Our study shows that some individuals with low levels of neutralizing antibodies have been re-infected, which may make people who have previously infected and recovered more susceptible to the new SARS-CoV. Shows sexuality. -2 Post-infection infection. As seen in the majority of participants, these reinfections can be asymptomatic. This can be between Navy units or the Navy. Important considerations for maintaining U.S. military operational readiness, including preventing future COVID-19 outbreaks on board .. The take-away message to all young people, including our military service members, is clear. Immunity from natural infections is not guaranteed. Even if you have COVID-19 and recover, you will still need to be vaccinated. “

The authors did not consider people with very low antibody levels after past infections, which may underestimate the risk of reinfection in previously infected individuals. Keep in mind the limitations (in the study, previously infected, but at a detectable level antibody In a baseline antibody level test).

In this study, participants dropped out more than usual (a total of 566 participants (34 recruits in the baseline seropositive group and 532 recruits in the baseline seronegative group) started basic training. And did not report follow-up 2-a few weeks later).The research team was not informed why the recruits did not return for follow-up, but this was for individuals who dropped out of the study, those who were removed from the base for medical reasons, or individuals who were separated from the United States. Marines said it could be a combination

Finally, the authors are unable to determine how serum-positive recruits were infected with a previous SARS-CoV-2 infection, confirm with PCR tests, or determine severity or symptoms. was. They also say they may have missed a detectable infection that occurred during the biweekly PCR test under study.

María Velasco of the Universitario Fundación Alcorcón Hospital in Spain said in a linked comment: “This study was conducted in a closed environment, but provides interesting insights into the risk of subsequent SARS-CoV-2 infection in the general population or in other environments. First, the new SARS-CoV-2. The proportion of PCR-positive results is about 80% lower among serum-positive individuals. These data are significant even though serum-positive individuals have limited protection against new infections. Is confirmed. […] Second, the detection rate of the new SARS-CoV-2 PCR in serum-positive Marine Corps cases is not negligible, even in the young and healthy population (1.1 cases per person per year). Globally, these results indicate that COVID-19 does not provide near-universal, long-term protective immunity like measles. “

She continued: “Efforts must be made to reduce the risk of SARS-CoV-2 infection from young oligosymptomatological individuals. The results of Letizia et al. Are young individuals with previous SARS-CoV-2. Even suggests. infection It should also be vaccinated to avoid less unnoticed sources of infection. ”