Covid-19 : Natural immunity versus vaccine immunity

It should not be necessary to write an article to demonstrate the superiority of natural immunity over vaccine immunity, but it is necessary in view of the many underhanded attacks that tend to make artificial immunity seem more effective. Furthermore, it is officially recommended to vaccinate people who have already been infected with Covid-19. Survivors of the 2003 SARS-CoV have cellular immune memory more than 17 years after infection. Numerous studies have explored humoral (antibody) and cellular immunity to SARS-CoV-2 after Covid-19 infection: it persists for at least one year (and even 14 months) in a robust manner in convalescents and would be of better quality than vaccine immunity: natural antibodies are more potent, have a broader spectrum, and are able to evolve against variants more efficiently than vaccine antibodies. These in vitro studies are confirmed by the protection against reinfections conferred by a primary infection, particularly in early and highly vaccinated countries such as Israel and the United Kingdom. Vaccination of a primo-infected person could also decrease the effectiveness of his natural immunity against future reinfections.

The natural immunity of a population should therefore be explored before proposing vaccination: up to 50% of the population may have been infected in some countries.

Introduction
It should not be necessary to write this article to demonstrate that natural immunity is superior to vaccine immunity: indeed, since the appearance of life on Earth, natural immunity has been developing in all living beings in response to predators and all this without vaccines! Innate immunity preceded adaptive immunity and allowed us to recognize foreign pathogens, eliminate them and maintain an immune memory1.
Until June 2020, innate immunity, related to the human innate and adaptive/acquired immune system, was recognized by the WHO as a key component of herd immunity to novel pathogens.
Until November 2020, the WHO admitted that immunity can be provided by infection or by vaccination, on November 13, 2020, the WHO affirms that herd immunity of a population can only be achieved by vaccination and not by natural infection. This is reaffirmed on December 31, 2020 for Covid-19, while recognizing that we do not know the threshold of vaccine coverage to be obtained to achieve this herd immunity. (only the December 31, 2020 definition is still accessible, https://www.who.int/news-room/q-adetail/herd-immunity-lockdowns-and-covid-19 , the previous ones are visible on the screenshot below) In a recent publication, the John Hopkins Institute only mentions vaccine immunity in a discussion about the hypothetical herd immunity to be expected against Covid2

Immunity to coronaviruses
The knowledge on the immunity acquired after a coronavirus infection is very insufficient.
In 1990, the only in vivo human experiment on acquired immunity to common cold coronaviruses was published3 : volunteers were infected with coronavirus 229E, which causes cold symptoms, and returned one year later to be re-exposed to the virus. Most people were re-infected, but those who had been sick the previous year did not develop cold symptoms. The study authors also reported that the period of virus shedding, when a person is infectious, was shorter in those who had been infected the previous year.
For 2003 SARS-CoV-1, cellular immunity has been shown to persist for 11 years according to a 2016 study4.
And according to a 2020 study, patients who survived the 2003 SARS outbreak have memory cell reactivity 17 years after the outbreak5.
Because SARS-CoV-2 causing Covid-19 is a closely related virus to 2003 SARS-CoV-1 and shares many similarities in epidemiology and pathogenicity, it is possible that cellular immunity to the Covid-19 virus could persist for years.

Immunity measured in vitro after infection with SARS-CoV-2
Studies comparing in vitro (antibody assay, neutralizing activity, memory B and T cells) natural and Qeios, CC-BY 4.0 · Article, October 1, 2021 Qeios ID: DP264J · https://doi.org/10.32388/DP264J 2/14 vaccine immunity seem to show superiority of natural immunity. It seems that vaccination modifies the immune response of convalescents and not necessarily in a good way: it could reduce the subsequent capacity of convalescents to react to future variants. Publications (examples below) show that neutralizing antibodies and memory B (humoral immunity) and T (cellular immunity) cells persist for at least one year in convalescents. Protection against SARS-CoV-2 infection could last for years6.

Humoral immunity (antibodies)
It is normal to observe a drop in circulating antibody levels after an infection, as happens with all infections, otherwise the blood would be thickened by all the antibodies that accumulate over a lifetime. At the same time, the immune memory is built and refined.
"The slight decrease in antibodies observed in convalescent individuals does not reflect a real decline in humoral immunity, but rather a contraction of the immune response, while maturation of antibody affinity occurs and anti-Spike memory B cells persist. "7 Several publications suggest that natural immune memory is even better than vaccine memory.
According to Cho et al. 8,natural antibodies are more potent and broader spectrum than vaccine antibodies. As discussed below, the neutralizing power of plasma measured in vitro is unlikely to be evidence of protection against infection.
Antibodies to the RBD (receptor binding domain) of the spike protein and to the whole spike persist for at least 1 year after recovery from Covid, and the level of anti-RBD antibodies correlates with the level of neutralizing antibodies9.
In vaccinated individuals, antibody levels decrease by 40% per month and by less than 5% per month in convalescents10.

Cellular immunity
In recovered COVID-19 patients, SARS-CoV-2-specific CD8+ T-cell responses remained largely intact and could recognize virtually all mutations of the variants studied11.
In dialysis patients, a German team found better humoral and cellular immunity in convalescents According to a meta-analysis of 18 studies of SARS-CoV-2 epitopes recognized by T cells of Covid-19 convalescents: The high diversity of epitopes not confined to the S protein does not appear to be affected by VOC variants, at least before the arrival of the delta variant14.
A recent Israeli publication of September 21, 2021, shows the persistence of humoral immunity in convalescents for 14 months, which is not the case in vaccinated individuals. Bypass of innate immunity by mRNA vaccines could affect the ability of the immune system to maintain sufficient levels of long-lived plasma cells15.

Protection against reinfection by infection acquired immunity
These in vitro observations of antibody and memory cell levels are well confirmed by looking for reinfections in convalescents: these are very rare.
Numerous publications (see for bibliography the recent BMJ article16 ) show that the rate of reinfection is very low (less than 1%) following a first infection with SARS-CoV-2. The vast majority of these reinfections are not reinfections as such since they are asymptomatic: they are simply nasal carriage of virus without systemic infection. This is not surprising for a cold virus; the nose is an immune sanctuary where blood antibodies do not circulate.

What is the proportion of people in the world who are naturally immune to infection?
There is patchy information: in Kenya in November 2020, more than 1/3 of the population was HIV positive17 ; in India in January 2021, 25% of the population was seropositive18. In China, in Wuhan, the epicenter of the epidemic, a very low rate of seropositivity has been found (less than 4% in April 202019).
Infected persons with few or no symptoms do not develop this type of SARS-CoV-2 specific antibodies, they would have been protected by their cross immunity to common cold coronaviruses23.
In France, the HAS estimates that 23% of the population has been infected while only 8% have been detected by PCR or antigenic test20.
It is estimated that almost half of all Americans have been infected with SARS-CoV-216 By August 2020, 40% of the Malagasy population (estimated from blood donors) would have been seropositive21.
One obstacle to these seroprevalence studies is that serological tests lack standardization22 .

Another problem is that one can be immune and not have antibodies (anti-S or other antibodies).
According to publications from 2020, people who are infected but have not developed symptoms have a T cell reaction but no antibodies23 (for a review); this is confirmed in 2021 : Le Bert et al. 24 search seropositive asymptomatics for anti-NP-IgG antibodies (antibodies to the virus nucleocapsid): all seropositives have a highly functional virus-specific cellular immune response. In addition, individuals who are anti-NP IgG negative also have T cells that react specifically with SARS-CoV-2 antigens.

What is a reinfection?
The CDC defines reinfection as a positive test regardless of symptoms (and unvaccinated people are tested more than vaccinated people, due to the health pass)25 . The only studies that claim that infection does not protect against reinfection do not clearly define the term reinfection: a positive PCR with a Ct of 35 (low viral load or false positive) without symptoms cannot be defined as reinfection.
The study of reinfections shows that infection provides at least as much protection against infection and probably more than vaccination. As early as April 2021, F Krammer proposed that natural immunity was better than vaccine immunity, based on a British study comparing primary infected and vaccinated healthcare workers26 .
Since this publication, the continuation of this SIREN study has concerned reinfections with the delta variant and shows the superiority of natural immunity27. Of the 9,831 healthcare workers who were already infected with Covid before the study began, 51 were reinfected between April and July 2021, the period of delta variant circulation. Among these 51 persons, 45 were vaccinated since at least 21 days after dose 1 or 14 days after dose 2, nothing is specified about the 6 remaining persons: either they were not vaccinated or, they were infected in the few days following dose 1 or 2 because of the ADE (antibody dependent enhancement = facilitation of infection by vaccine antibodies): why is it not specified? All in all, infection protects against reinfection, which is not the case with vaccination According to a French study, the relative reduction in the incidence of reinfection by SARS-CoV-2 is 96.7% in convalescents28 compared with non-infected people.
In  This study was reported in Science Mag and summarized as follows: Israelis who had an infection were more protected against the Delta variant of the coronavirus than those who received a COVID-19 vaccine32.

Meta-analysis of natural immunity data (September 21, 2021)33
Natural immunity is equivalent to or superior to vaccination in protecting against Covid: no study concludes that vaccine protection is superior to natural immunity with statistical certainty, but observational studies have confirmed the benefit of protection by natural immunity.
The benefit of vaccinating people who have already contracted Covid is zero or very small (3 out of 4 studies find no benefit of vaccinating convalescents and the additional protection found by pooling all studies is 0.004%).
Vaccine immunity is classically associated with the titer of neutralizing antibodies in vitro, but are neutralizing antibodies the right correlate of protection?
There are conflicting results on the persistence of neutralizing antibodies after infection: in some studies these antibodies persist for at least one year, in others their level decreases rapidly, perhaps due to the methods used, which differ from one study to another?
To measure the neutralizing power of a serum in vitro, these studies use either live viruses cultured on different types of cells, or reconstituted pseudoviruses carrying mutated spike proteins of SARS-CoV-2 on their surface.
According to a meta-analysis34, the levels of neutralizing antibodies induced by mRNA vaccines against SARS-CoV-2 variants were similar to or higher than those obtained from naturally infected individuals. This

Immune memory concerns other epitopes than those of the spike
Almost all of the studies concern anti-spike antibodies, however, "The majority of epitopes targeted by CD8+ are found in the internal proteins of the virus or in the NSPs [non-structural proteins, which do not include the spike protein]"43 Protection from infection is likely due as much to immune memory as to persistence of high antibody levels44

Neutralizing antibodies may lose their properties in the presence of facilitating antibodies produced by vaccination
The present article cannot elaborate on this subject, which has been discussed in recent publications45 The role of mucosal immunity, which is stimulated by natural infection and not by IM vaccination, should also be mentioned: "Almost all studies of the immune response in COVID-19 have focused exclusively on serum antibodies and systemic cell-mediated immunity, including innate responses. Mucosal immunity and secretory and circulating IgA antibodies play an important role in COVID-19, and it is important to elucidate this in order to understand in particular the asymptomatic and mild states of infection, which appear to represent the majority of cases. "46 "Vaccination of never-infected persons may not induce strong humoral immunity in the respiratory mucosa, because neutralizing antibodies to SARS-CoV-2 are rarely detected in nasal swabs from vaccinated persons. If it turns out that current vaccination strategies fail to elicit robust humoral and cellmediated immune responses in the respiratory tract, then strategies to better elicit SARS-CoV-2-specific B and T cells in the mucosa of never-infected individuals should be considered-for example, by implementing intranasal mRNA immunization, which is more likely to induce sterilizing immunity. "47 Protection against Covid may also be due to cross-immunity to common cold coronaviruses23 .
A recent study shows that children have SARS-CoV-2 reactive cells in their tonsils, even though they have Qeios,.0 · Article, October 1, 2021 Qeios ID: DP264J · https://doi.org/10.32388/DP264J 7/14 not been exposed to the virus, so pre-existing cellular cross-immunity may explain their resistance to Covid48.

Is it appropriate to vaccinate Covid convalescents?
The case of long Covids49 Two theories explain long covids: either the virus persists and causes chronic inflammation, or it is autoimmunity through the production of autoantibodies against viral proteins with similarities to human proteins. Vaccination can aggravate this phenomenon but also improve it, we do not know this in advance.
mRNA vaccines aberrantly direct T-cell responses in patients with neurological sequelae of Covid infection (Covid long): is it appropriate to vaccinate them?50

Adverse effect of vaccine on ability to respond to new variants
Vaccination of convalescent subjects may be risky: convalescent subjects have more systemic adverse events than naı̈ve subjects after the first dose of vaccine.51 In addition, vaccination does not improve the ability to respond to new variants and may even be harmful.
One study found somewhat contradictory results: vaccination increased humoral and memory response in convalescents by 30 to 50 times. The neutralizing activity in unvaccinated convalescents is weakened against the variants (the delta variant is not tested) but increased after vaccination in convalescents.
The neutralization spectrum of antibodies collected in convalescents broadens with time and after one year the potency and neutralization spectrum are increased against the variants Vaccination does not broaden the spectrum of clonal expansion compared to unvaccinated convalescents after one year. RBDbinding antibody affinity is not increased by vaccination after one year, no difference in neutralizing effect is observed.52 The second dose of BNT162b2 vaccine results in a reduction in cellular immunity in persons who have recovered from COVID-19, suggesting that a second dose, according to the current standard vaccination regimen, may not be necessary in persons previously infected with SARS-CoV-2: the second dose of vaccine not only does not enhance humoral immunity, but also determines a contraction of the spike-specific T-cell response.53 The natural immunity of the infected is hampered by a subsequent anti-Covid vaccination Vaccination of convalescents reduces the ability to produce broad-spectrum antibodies against future variants; unvaccinated convalescents have this ability.54 The affinity of natural antibodies increases more with time than that of vaccine antibodies After vaccination of primary patients, the level of neutralizing antibodies increases, but not the potency of these antibodies or the ability to evolve to broad-spectrum protection thereafter. This is also true for the delta variant.

The difference in memory cell compartments in response to infection or vaccination (mRNA) is consistent with the greater level of protection conferred by natural infection with the variants.
A relative reduction in reactivity of sera with the B.1.1.7 variant compared to the Wuhan-1 variant is seen after the second booster immunization. These data allow comparison of the different vaccines in terms of anti-S antibody production and call into question the value of repeated immunization with the same S The CD4+ T cell response is decreased in convalescents after vaccination compared to naı̈ve individuals: vaccination is thought to damage the T cell response. After vaccination, the magnitude of the immune response appears to be lower in convalescents than in naı̈ve individuals56.
Pfizer's vaccine could reshape the innate immune response to other pathogens. It would induce immune tolerance that could either be beneficial in Covid-19 characterized by hyperinflammation or be deleterious by decreasing the response to other viral infections [and cancers]. This vaccine could also interfere with other vaccinations such as influenza, which is likely to be given at the same time in early fall57.
This reprogramming of immune immunity could be long-lasting due to epigenetic phenomena: "Training" of the innate immune response plays an important role both in diseases where host defense is impaired, such as cancers, and in autoinflammatory and autoimmune diseases, in which an exacerbated "trained" immunity phenotype could contribute to the pathogenesis of the disease. The impact of immune training, and more generally of epigenetic rewiring in the various priming, adaptation, or tolerance processes during disease, deserves further study. "58

Conclusion
Natural immunity to Covid-19 (i.e., obtained after natural infection with the virus) is therefore certainly robust and durable.
Work on post-vaccination immunity is mainly concerned with so-called "neutralizing" antibodies in vitro.
The levels of these antibodies may not be a good correlate of protection because studies often find higher levels of antibodies after vaccination than after infection. However, reinfections are much more frequent in vaccinated patients than in convalescents. Protection against Covid-19 could rather depend on immune memory (due to memory T and B cells that persist long after infection) and seems to be of better quality than that conferred by vaccines.
In addition, vaccination of convalescent subjects could be risky: more systemic adverse events are observed in convalescent subjects than in naı̈ve subjects after the first dose of vaccine.
Vaccination may decrease the ability to respond to future variants. It could also have a non-specific effect of remodeling the innate immune response by decreasing the potential response to other viruses or to cancers and by modifying the course of inflammatory and autoimmune diseases.