When the terms “natural immunity” or “naturally-derived immunity” are used, this isn’t in reference to one’s “innate” immune system, but to one’s “adaptive” immune system that has been educated regarding what to attack in the future after being exposed to previous infection(s) – the COVID-19 virus in the case of the current pandemic. God designed the human immune system to remember, learn and improve over time as it fights off more and more invaders – so that it becomes more and more effective with each successful battle. The question that many people have, including doctors and scientists who are trying to fight this pandemic, is if previous infection(s) by COVID-19 produce levels of immunity in people comparable to vaccination? – such as with the modern mRNA vaccines?
Well, the evidence seems reasonably clear at this point, at least to me, that “natural immunity”, derived from a previous COVID-19 infection, is indeed at least as good as the immunity gained from being fully vaccinated via one of the mRNA vaccines (Moderna and even more so vs. Pfizer).
There are several lines of scientific evidence that seem to strongly support this conclusion – particularly since the Delta and Omicron variants of COVID-19 came on the scene. For example, consider a study published by the CDC in January of 2022, covering a period of time from May 30 to November 13, 2021 (Link). This study found that those who had survived prior COVID-19 infections were just as protected against serious infections requiring hospitalization as those who were fully vaccinated.
Clearly, the only group of people (among the four groups included in this graph) that is significantly more at risk than the others are those who are unvaccinated and who have had no previous history of a COVID-19 infection. This particular group of people had a much higher risk of serious infection compared to the other three groups of people.
This is consistent with a large Israeli study (covering a period of time from March 1, 2020 to August 14, 2021) that showed that natural immunity is 13 times more effective than vaccination (the Pfizer vaccine in particular) in protecting individuals from future severe COVID-19 infections.
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. (Sivan Gazit, et al., August 2021)
Now, there are those who argue that even though natural immunity may be stronger and even more long-lasting than vaccine-derived immunity against COVID-19, that the vaccine-derived immunity is more consistent. While this may be true to at least some degree, it doesn’t seem to be all that significant – at least not based on the weight of evidence that is currently in hand as best as I can tell. Smaller CDC studies, for example, that appear to show greater and longer-lasting benefits for the vaccines vs. naturally-derived immunity don’t seem to effectively counter the data described above.
And, I’m not the only one who sees the data this way. For instance, Dr. Marty Makary, a professor at Johns Hopkins University School of Medicine and editor in chief of MedPage Today, argues that mandating vaccines for “every living, walking American” is, as of now, not well-supported by science. He also interprets the current data as showing strong support for natural immunity. He cites over 15 different studies along these lines showing that natural immunity seems to provide even better protection against future severe COVID-19 infections than the vaccines – and therefore should be acknowledged by public health officials (Link).
This is not to say that natural immunity makes the vaccines against COVID-19 irrelevant or useless. That’s not what this data is saying at all. Clearly, for those who haven’t yet been infected, getting vaccinated before exposure to COVID-19 is far far less risky, for every age category, compared to getting infected by COVID-19. Just to highlight this reality, note that the Intensive Care National Audit & Research Centre, or ICNARC, just updated their analysis of COVID patients who required critical care in England, Wales and Northern Ireland from May through December of 2021. On this chart, they now show boosted patients as well. They are shown in green. Yes, they are on the chart. You have to squint (Link).
However, for those who have already gone through a COVID-19 infection, vaccinated or not, the resulting immunity derived from that infection should be recognized as being at least equivalent, if not better, to getting vaccinated – over an equivalent span of time.
This is why some countries, including the member states of the European Union, are starting to treat documented recovery from COVID-19 as functionally the same as vaccination in their “vaccine passport” systems (Link).
Still, vaccine-induced immunity is a better choice, not because it produces a stronger immunity, but because it enables you to get the immunity without the side effects and risks that come along with illness — like a greater risk of stillbirth if you’re pregnant, or long COVID, hospitalization and death in general. (Koerth, Jan. 19, 2022)
What this also suggests is that the current surge of the Omicron variant of COVID-19, being far more infectious than any prior variant (while thankfully being less severe than the Delta Variant), might end up as a form of default vaccination, like it or not, for everyone that it infects. This suggests that the Omicron variant may be the means to ending the entire pandemic – which would be a blessing in disguise. I’m hopeful anyway…
So, in summary, if you haven’t already had COVID-19, get vaccinated. While Omicron is less severe than Delta, it is still making many sick enough to require hospitalization and, right now, more than 3,000 people are being killed by Omicron every day – with many more suffering long-term, even permanent, injuries. However, if you have already had COVID-19, you probably don’t need to get vaccinated, at least not from a scientific perspective. Personally, though, I would consider getting a booster shot after 6 months to a year. Now, for those who with naturally-derived immunity who might still need to get a vaccine earlier than this (for political reasons or to travel or for any other reason beyond the scientific evidence itself) I would personally recommend getting the lowest dose available – which is the Pfizer vaccine with its 30 µg dose per vaccination (as compared to the 100 µg dose for the first two Moderna vaccines and the 50 µg Moderna booster). As a silver lining, those who have been previously infected by COVID-19 and who then get at least one mRNA vaccine, end up with the highest levels of immunity against future infections. For me personally, if I had been infected before having a chance to be vaccinated, I would still choose to get at least one Pfizer vaccine – just to be sure. Fortunately, I was able to get fully vaccinated, and boosted, without having to risk the actual infection itself with a completely naïve immune system.
Dr. Sean Pitman is a pathologist, with subspecialties in anatomic, clinical, and hematopathology, currently working in N. California. He’s also a life-long Seventh-day Adventist, the son of a retired SDA minister, and is very active in his local church.