I previously wrote about the Israeli study which found that natural immunity provides much better protection against infection than the Pfizer vaccine.
Sivan Gazit and colleagues tracked two groups of people over time: fully vaccinated people who’d never tested positive; and unvaccinated people who had tested positive. Of the 257 cases that were detected at follow-up, 93% occurred in the vaccinated group, and only 7% occurred in the previously infected group.
And indeed, a recent systematic review (which has not yet been peer-reviewed) confirms that natural immunity confers a very high degree of protection against infection. The researchers analysed 10 studies, and found that the “weighted average risk reduction against reinfection was 90.4%”.
Compare this to studies of the vaccines’ efficacy against infection. In July, the Israeli Ministry of Health reported that the Pfizer vaccine’s effectiveness had dropped to just 39%. And a pre-print study by Qatari researchers found that it fell to zero after six months. (Though the vaccines’ efficacy against severe diseases appears to hold up well.)
Adding to the evidence outlined above, there are now studies comparing natural and vaccine-induced immunity at the cellular level.
I should mention that I am not qualified to evaluate the methods used by these studies, so I will have to assume the authors have done things properly. With that qualification in mind, it’s worth briefly discussing what they found.
In a recent paper published in Cell Reports, researchers from Minneapolis compared the memory B cells generated after natural infection versus mRNA vaccination. Memory B cells (MBCs) are part of the adaptive immune system; they are responsible for recognising antigens, and triggering a secondary immune response.
The researchers found that “infection-induced primary MBCs have better antigen-binding capacity and generate more plasmablasts and secondary MBCs of the classical and atypical subsets than vaccine-induced primary MBCs”. As a result, infection-induced MBCs “produce more robust secondary responses”.
In a second study, published as a preprint, researchers from Boston compared the durability and breadth of antibodies after natural infection versus mRNA vaccination. They found that infection-induced antibodies “exhibited superior stability and cross-variant neutralisation breadth than antibodies induced by a two-dose mRNA regimen”.
In other words, individuals who’d already been infected had better immunity against the then-novel Delta variant, as compared to ‘naïve’ individuals who’d received an mRNA vaccine.
Taken together, the statistical and immunological evidence suggests that natural immunity provides better protection against infection than the mRNA vaccines. This does not mean that nobody stands to benefit from vaccination. The vaccines are still an important way of achieving focused protection for high-risk groups.
But it does undermine the case for vaccine passports, and for vaccinating 12-15 year-olds. As Jay Bhattacharya wrote back in July: “Any infection-blocking effects are probably short-term unless the vaccine does very much better than natural immunity, which is rare in medicine.”