Natural immunity is a hot topic with regards to COVID-19. Many debates the world over have argued both sides of the issue. The prevailing mainstream narrative seems to suggest that vaccine induced immunity is best, which is why those who have natural immunity from a prior COVID-19 infection must still receive a full course of vaccination in order, for example, to qualify for a vaccine passport. The question is, what does the science say? Should you still get a vaccine if you have previously been infected by COVID-19?

The NSCLA is not advocating a strategy of natural immunity (attempting to get infected rather than being vaccinated). Rather, we are simply assessing the science of the robustness of the immune response between those who have received a vaccine, and those who have already been infected. Let's see what the science says.


The CDC Confirms Natural Immunity is Superior Against Delta

In a study released January 19, 2022 the CDC has confirmed that by early October 2021 (Delta had been dominant in the US since June), persons who recovered from a previous COVID-19 infection (natural immunity) had 3x lower case rates and more than 2x lower risk of hospitalization than persons who were vaccinated and had not previously recovered from infection.  Using the CDC data from California, an unvaccinated person who had a previously diagnosed COVID-19 infection had a 0.5% chance of becoming re-infected. If re-infected, that person had a 5.5% chance of hospitalization. This equates to an absolute risk of hospitalization of 0.03% for an average person who is unvaccinated but has had a previous COVID-19 infection. Regarding a vaccinated person who has not had a previous infection, their risk of becoming infected was 1.5%. If infected, their risk of hospitalization was 4.5%. This equates to an absolute risk of hospitalization of 0.067%.

The Lancet Concludes 80-100% Reduction in Risk of Re-infection with Natural Immunity

A study published in The Lancet in November, 2021 analyzed a plethora of high quality studies from around the world (mainly based on Delta) and found that the risk of repeat SARS-CoV-2 infection decreased by 80–100% among those who had COVID-19 previously. The Lancet also reported on another laboratory-based study that analyzed the test results of 9119 people with previous COVID-19 infection from Dec 1, 2019, to Nov 13, 2020, which found that only 0.7% became re-infected. In a study conducted at the Cleveland Clinic in Cleveland, OH, 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 effectively 0 per 100 people. Furthermore, a study conducted in Austria found that the frequency of hospitalisation due to a re-infection was just 0.03% (3/10000 people) and the frequency of death due to a re-infection was 0.007% (1/14840 people).

Nature Confirms Long-Lived antigen specific Natural Immunity

A study published in Nature in May, 2021 concludes that, whilst levels of anti-SARS-CoV-2 serum antibodies decrease rapidly in the first few months after COVID-19 infection, the study results indicate that even mild infection with SARS-CoV-2 induces robust antigen-specific, long-lived humoral immune memory via bone marrow plasma cells (BMPC) and memory B cells. Note, this study was published prior to Delta being dominant. SARS-CoV-2 S-specific BMPCs were detected in 79% of participants 11 months post COVID-19 infection SARS-CoV-2 S-specific BMPCs were found in 0% of those who had no prior infection.

146 Studies Verify Robustness of Natural Immunity

The Brownstone Institute has compiled 146 studies that verify the robustness of natural immunity against COVID-19. The general conclusion is simple - if you had a previous COVID-19 infection, your immunity will be long-lasting and of a broader nature than from vaccination alone. This is because vaccine induced immunity is narrowly focused on a single spike protein, making it ripe for new variants to mutate just enough to escape that immunity. Natural immunity, however, is more broad because antibodies are created based on multiple aspects of the virus, making it much more difficult for new variants to mutate enough to escape the robustness of the immunity. We also know know vaccine induced immunity starts strong, but wanes very quickly, hence the necessity of a booster does 6 months after a previous dose. On the other hand, natural immunity provides robust antigen-specific protection for at least 11 months, and quite likely far longer. Memory T cells that are reactive to the N protein of SARS-CoV(1) 17 years after the outbreak of SARS in 2003 also displayed robust cross-reactivity to the N protein of SARS-CoV-2.