Natural Immunity and Covid-19

Innate and Adaptive Immunity

Every day we are alive, humans encounter potentially harmful disease causing organisms, or “pathogens”, like bacteria or viruses. Yet all of us as long as we have a adequate nutrition and are not exposed to a toxic environment or have compromised immune systems due too underlying diseases or treatments of these, are still able to function properly and live life without constantly being sick. That’s because the human body has a multilayered immune system to keep it running smoothly. This is what is called our natural immunity.

In basic terms, the immune system has two lines of defense: innate immunity and adaptive immunity. Innate immunity is the first immunological, non-specific (antigen-independent) mechanism for fighting against an intruding pathogen. It is a rapid immune response, occurring within minutes or hours after aggression, that has no immunologic memory. Adaptive immunity, on the other hand, is antigen-dependent and antigen-specific; it has the capacity for memory, which enables the host to mount a more rapid and efficient immune response upon subsequent exposure to the antigen. There is a great deal of synergy between the adaptive immune system and its innate counterpart, and defects in either system can provoke illness or disease, such as autoimmune diseases, immunodeficiency disorders and hypersensitivity reactions. This article provides a practical overview of innate and adaptive immunity, and describes how these host defense mechanisms are involved in both health and illness (read more here).

It has been well known for over a century that when the body is exposed to a viral pathogen it builds a strong lifelong immunity against disease. This is why doctors best advice to the mothers of children, unless they were immun compromised, was to mingle with other children with childhood diseases.

Like for other viral diseases the corona family of viruses also confers strong and probably lifelong immunity to disease. Observations of persons with SARS1 showed that they had adaptive immunity 17 years after exposure.

It was observed early in the outbreak of SARS-CoV-2 that we demonstrated that the T and B cells are activated naturally and are functional during SARS-CoV-2 infection. and that the adaptive immunity in most patients is rimed to induce a significant immune response against SARS-CoV-2 infection.

Immunology and virology 101 have taught us over a century that natural immunity confers protection against a respiratory virus’s outer coat proteins, and not just one, e.g. the SARS-CoV-2 spike glycoprotein. There is even strong evidence for the persistence of antibodies. Even the CDC recognizes natural immunity for chicken-pox and measles, mumps, and rubella, It seems reasonable therefore that mandated COVID-19 vaccines must be seen as unethical when it is clear that naturally acquired immunity is equal to or more robust than vaccination (read more here).  

Covid-19- Natural immunity versus Vaccine Induce Immunity

The World Health Organization in a Scientific Brief on Covid-19 dated May 10, 2020 based on a literature review states the following:

  1. The strength and duration of the immune responses to SARS-CoV-2 are not completely understood
  2. Data suggests that it varies by age and the severity of symptoms.
  3. Available scientific data suggests that in most people immune responses remain robust and protective against reinfection for at least 6-8 months after infection.
  4. Within 4 weeks following infection, 90-99% of individuals infected with the SARS-CoV-2 virus develop detectable neutralizing antibodies.
  5. Some variant SARS-CoV-2 viruses with key changes in the spike protein have a reduced susceptibility to neutralization by antibodies in the blood.
  6. While neutralizing antibodies mainly target the spike protein, cellular immunity elicited bynatural infection also target other viral proteins, which tend to be more conserved across variants than the spike protein.
  7. There are many available serologic assays that measure the antibody response to SARS-CoV-2 infection, but at the present ntime, the correlates of protection are not well understood.

A 2007 study from China (1) found that among 176 patients who had had severe acute respiratory syndrome (SARS-1), SARS-specific antibodies were maintained for an average of 2 years, and significant reduction of immunoglobulin G–positive percentage and titers occurred in the third year concluding that SARS patients might be susceptible to reinfection >3 years after initial exposure.

Reports of waning vaccine-induced immunity against falling antibody titers against COVID-19 became apparent early into the mass vaccination campaign but knowledge comparing long-term immunity conferred by the experimental biological products compared to previous infection with SARS-CoV-2 was not forthcoming.

Sivan Gazit and co-worker did a study to understand to compare SARS-CoV-2 natural immunity to vaccine-induced immunity: reinfections versus breakthrough infections in Israel.

This retrospective observational study compared three groups: (1)SARS-CoV-2-naïve individuals who received a two-dose regimen of the BioNTech/Pfizer mRNA BNT162b2 vaccine, (ii)previously infected individuals who have not been vaccinated, and (iii) previously infected and single dose vaccinated individuals. Three multivariate logistic regression models were applied. In all models four outcomes were evaluated: (i) SARS-CoV-2 infection, (ii) symptomatic disease, (iii) COVID-19-related hospitalization and (iv) death. The follow-up period of June 1 to August 14, 2021, when the Delta variant was dominant in Israel.

SARS-CoV-2-naïve vaccinees had a 13.06-fold (95% CI, 8.08 to 21.11) increased risk for breakthrough infection with the Delta variant compared to those previously infected, when the first event (infection or vaccination) occurred during January and February of 2021. The increased risk was significant (P<0.001) for symptomatic disease as well. When allowing the infection to occur at any time before vaccination (from March 2020 to February 2021), evidence of waning natural immunity was demonstrated, though SARS-CoV-2 naïve vaccinees had a 5.96-fold (95% CI, 4.85 to 7.33) increased risk for breakthrough infection and a 7.13-fold (95% CI, 5.51 to 9.21) increased risk for symptomatic disease. SARS-CoV-2-naïve vaccinees were also at a greater risk for COVID-19-related-hospitalizations compared to those that were previously infected.

This study demonstrated that natural immunity confers longer lasting and stronger protection against infection, symptomatic disease and hospitalization caused by the Delta variant of SARS-CoV-2, compared to the BNT162b2 two-dose vaccine-induced immunity.


  1. Li-Ping Wu, Nai-Chang Wang, Yi-Hua Chang, Xiang-Yi Tian, Dan-Yu Na, Li-Yuan Zhang, Lei Zheng, Tao Lan, Lin-Fa Wang, and Guo-Dong Liang. Duration of Antibody Responses after Severe Acute Respiratory Syndrome. Emerg Infect Dis. 2007 Oct; 13(10): 1562–1564.doi: 10.3201/eid1310.070576
  2. Sivan Gazit, Roei Shlezinger, Galit Perez, Roni Lotan, Asaf Peretz, Amir Ben-Tov, Dani Cohen, Khitam Muhsen, Gabriel Chodick, Tal Patalon. Comparing SARS-CoV-2 natural immunity to vaccine-induced immunity: reinfections versus breakthrough infections. doi: