Kojima-2022-Protective Immunity After Recovery

Since January 2020 Elsevier has created a COVID-19 resource center with free information in English and Mandarin on the novel coronavirus COVID-19. The COVID-19 resource center is hosted on Elsevier Connect, the company's public news and information website.

Elsevier hereby grants permission to make all its COVID-19-related research that is available on the COVID-19 resource center - including this research content - immediately available in PubMed Central and other publicly funded repositories, such as the WHO COVID database with rights for unrestricted research re-use and analyses in any form or by any means with acknowledgment of the source. These permissions are granted for free by Elsevier for as long as the COVID-19 resource center remains active.

The novel coronavirus (COVID-19) can affect the normal function of the immune system, which is one of the first defense mechanisms against viral infection.

Viral infection triggers an immune system response, including inflammation and antibody production. However, the pathogenic mechanism of COVID-19 is complicated. The virus attacks important cells of the immune system, such as T cells and B cells, disrupting their normal function. At the same time, COVID-19 can also cause an excessive immune response, causing the immune system to attack healthy cells of the body, producing a severe inflammatory response manifested as a cytokine storm, and even causing further damage and death.

Immunological research on COVID-19 is therefore ongoing to gain insight into how immune responses are regulated and how to ensure effective immune responses while avoiding overreactions.

Additionally, some studies have shown that the health of the immune system can affect the severity of a COVID-19 infection. There are people with weakened immune systems in the population, such as the elderly, people with underlying diseases, and immunocompromised patients. These people are at higher risk of contracting COVID-19 and may have more severe symptoms. Therefore, maintaining an adequate and healthy immune system plays an important role in preventing the onset and severity of COVID-19.

In conclusion, there is a complex and important relationship between COVID-19 and the immune system that requires further research and understanding. At the same time, maintaining a healthy immune system is also one of the important measures for the prevention and control of COVID-19. From this point of view, we need to improve our immunity to resist viruses. Cistanche can significantly improve immunity, and the polysaccharides in meat can regulate the immune response of the human immune system, improve the stress ability of immune cells, and enhance immunity. Bactericidal effect on cells.

Click cistanche deserticola supplement

Protective immunity after recovery from SARS-CoV-2 infection

The SARS-CoV-2 pandemic is now better controlled in settings with access to fast and reliable testing and highly effective vaccination rollouts. Several studies have found that people who recovered from COVID-19 and tested seropositive for anti-SARS-CoV-2 antibodies have low rates of SARS-CoV-2 reinfection. There are still looming questions surrounding the strength and duration of such protection compared with that from vaccination.

Biological studies

• Dan et al (2021):1 About 95% of participants tested retained immune memory at about 6 months after having COVID-19; more than 90% of participants had CD4+ T-cell memory at 1 month and 6–8 months after having COVID-19.

• Wang et al (2021):2 participants with a previous SARS-CoV-2 infection with an ancestral variant produce antibodies that cross-neutralize emerging variants of concern with high potency.

Epidemiological studies

• Hansen et al (2021):3 In a population-level observational study, people who had had COVID-19 previously were around 80·5% protected against reinfection.

• Pilz et al (2021):4 In a retrospective observational study using national Austrian SARS-CoV-2 infection data, people who had had COVID-19 previously were around 91% protected against reinfection.

• Sheehan et al (2021):5 In a retrospective cohort study in the USA, people who had had COVID-19 previously were 81·8% protected against reinfection.

• Shrestha et al (2021):6 In a retrospective cohort study in the USA, people who had had COVID-19 previously were 100% protected against reinfection.

• Gazit et al (2021):7 In a retrospective observational study in Israel, SARS-CoV-2-naive vaccinees had a 13·06-times increased risk for breakthrough infection with the delta (B.1.617.2) variant compared with those who had had COVID-19 previously; evidence of waning natural immunity was also shown.

• Kojima et al (2021):8 In a retrospective observational cohort of laboratory staff routinely screened for SARS-CoV-2, people who had had COVID-19 previously were 100% protected against reinfection.

Clinical studies

• Hall et al (2021):9 In a large, multicentre, prospective cohort study, having had COVID-19 previously was associated with an 84% decreased risk of infection.

• Letizia et al (2021):10 in a prospective cohort of US Marines, seropositive young adults were 82% protected against reinfection.

We reviewed studies published in PubMed from inception to Sept 28, 2021, and found well-conducted biological studies showing protective immunity after infection (panel). Furthermore, multiple epidemiological and clinical studies, including studies during the recent period of predominantly delta (B.1.617.2) variant transmission, found that the risk of repeat SARS-CoV-2 infection decreased by 80·5–100% among those who had had COVID-19 previously (panel). The reported studies were large and conducted throughout the world. 

Another laboratory-based study that analyzed the test results of 9119 people with previous COVID-19 from Dec 1, 2019, to Nov 13, 2020, found that only 0·7% became reinfected.11 In a study conducted at the Cleveland Clinic in Cleveland, OH, USA, those who had not previously been infected had a COVID-19 incidence rate of 4·3 per 100 people, whereas those who had previously been infected had a COVID-19 incidence rate of 0 per 100 people.6 

 Furthermore, a study conducted in Austria found that the frequency of hospitalization due to a repeated infection was five per 14840 (0·03%) people, and the frequency of death due to a repeated infection was one per 14840 (0·01%) people.4 Due to the strong association and biological basis for protection,12 clinicians should consider counseling recovered patients on their risk for reinfection and document previous infection status in medical records.

Although those studies show that protection from reinfection is strong and persists for more than 10 months of follow-up,3 it is unknown how long protective immunity will truly last. Many systemic viral infections, such as measles, confer long-term, if not lifelong, immunity, whereas others, such as influenza, do not (due to changes in viral genetics).4 We are limited by the length of current reported follow-up data to know with certainty the expected duration that previous infection will protect against COVID-19. Encouragingly, authors of a study conducted among recovered individuals who had experienced mild SARS-CoV-2 infection reported that mild infection induced a robust antigen-specific, long-lived humoral immune memory in humans.13

It is important to note that antibodies are incomplete predictors of protection. After vaccination or infection, many mechanisms of immunity exist within an individual not only at the antibody level but also at the level of cellular immunity.14–16 It is known that SARS-CoV-2 infection induces specific and durable T-cell immunity, which has multiple SARS-CoV-2 spike protein targets (or epitopes) as well as other SARS-CoV-2 protein targets. The broad diversity of T-cell viral recognition serves to enhance protection to SARS-CoV-2 variants,15 with recognition of at least the alpha (B.1.1.7), beta (B.1.351), and gamma (P.1) variants of SARS-CoV-2.17 Researchers have also found that people who recovered from SARS-CoV infection in 2002–03 continue to have memory T cells that are reactive to SARS-CoV proteins 17 years after that outbreak.15 Additionally, a memory B-cell response to SARS-CoV-2 evolves between 1·3 and 6·2 months after infection, which is consistent with longer-term protection.18

Some people who have recovered from COVID-19 might not benefit from COVID-19 vaccination.6,19 In fact, one study found that previous COVID-19 was associated with increased adverse events following vaccination with the Comirnaty BNT162b2 mRNA vaccine (Pfizer– BioNTech).20 In addition, there are rare reports of serious adverse events following COVID-19 vaccination.21 In Switzerland, residents who can prove they have recovered from a SARS-CoV-2 infection through a positive PCR or other test in the past 12 months are considered equally protected as those who have been fully vaccinated.22

Although longer follow-up studies are needed, clinicians should remain optimistic regarding the protective effect of recovery from previous infections. Community immunity to control the SARS-CoV-2 epidemic can be reached with acquired immunity due to either previous infection or vaccination. Acquired immunity from vaccination is certainly much safer and preferred. Given the evidence of immunity from previous SARS-CoV-2 infection, however, policymakers should consider recovery from previous SARS-CoV-2 infection equal to immunity from vaccination for purposes related to entry to public events, businesses, the workplace, or travel requirements.

NK has received consulting fees from Curative. JDK serves as an independent medical director of Curative.

Reference

1 Dan JM, Mateus J, Kato Y, et al. Immunological memory to SARS-CoV-2 assessed for up to 8 months after infection. Science 2021; 371: eabf4063. 

2 Wang L, Zhou T, Zhang Y, et al. Ultrapotent antibodies against diverse and highly transmissible SARS-CoV-2 variants. Science 2021; 373: eabh1766. 

3 Hansen CH, Michlmayr D, Gubbels SM, Mølbak K, Ethelberg S. Assessment of protection against reinfection with SARS-CoV-2 among 4 million PCR-tested individuals in Denmark in 2020: a population-level observational study. Lancet 2021; 397: 1204–12. 

4 Pilz S, Chakeri A, Ioannidis JP, et al. SARS-CoV-2 re-infection risk in Austria. Eur J Clin Invest 2021; 51: e13520. 

5 Sheehan MM, Reddy AJ, Rothberg MB. Reinfection rates among patients who previously tested positive for COVID-19: a retrospective cohort study. Clin Infect Dis 2021; published online March 15. https://doi.org/10.1093/ cid/ciab234. 

6 Shrestha NK, Burke PC, Nowacki AS, Terpeluk P, Gordon SM. The necessity of COVID-19 vaccination in previously infected individuals. medRxiv 2021; published online June 19. https://doi.org/10.1101/2021.06.01.21258176 (preprint). 

7 Gazit S, Shlezinger R, Perez G, et al. Comparing SARS-CoV-2 natural immunity to vaccine-induced immunity: reinfections versus breakthrough infections. medRxiv 2021; published online Aug 25. https://doi. org/10.1101/2021.08.24.21262415 (preprint). 

8 Kojima N, Roshani A, Brobeck M, Baca A, Klausner JD. Incidence of severe acute respiratory syndrome coronavirus-2 infection among previously infected or vaccinated employees. medRxiv 2021; published online July 8. https://doi.org/10.1101/2021.07.03.21259976 (preprint). 

9 Hall VJ, Foulkes S, Charlett A, et al. SARS-CoV-2 infection rates of antibody-positive compared with antibody-negative health-care workers in England: a large, multicentre, prospective cohort study (SIREN). Lancet 2021; 397: 1459–69. 

10 Letizia AG, Ge Y, Vangeti S, et al. SARS-CoV-2 seropositivity and subsequent infection risk in healthy young adults: a prospective cohort study. Lancet Respir Med 2021; 9: 712–20. 

11 Qureshi AI, Baskett WI, Huang W, Lobanova I, Naqvi SH, Shyu CR. Re-infection with SARS-CoV-2 in patients undergoing serial laboratory testing. Clin Infect Dis 2021; published online April 25. https://doi. org/10.1093/cid/ciab345. 

12 Goel RR, Apostolidis SA, Painter MM, et al. Distinct antibody and memory B cell responses in SARS-CoV-2 naïve and recovered individuals following mRNA vaccination. Sci Immunol 2021; 6: eabi6950. 

13 Turner JS, Kim W, Kalaidina E, et al. SARS-CoV-2 infection induces long-lived bone marrow plasma cells in humans. Nature 2021; 595: 421–25. 

14 Doshi P. Covid-19: do many people have pre-existing immunity? BMJ 2020; 370: m3563. 

15 Le Bert N, Tan AT, Kunasegaran K, et al. SARS-CoV-2-specific T cell immunity in cases of COVID-19 and SARS, and uninfected controls. Nature 2020; 584: 457–62.

For more information:1950477648nn@gmail.com