Comparing Coronavirus Natural Immunity to mRNA Vaccine-Induced Immunity; the Debate Rages On

Researchers in Israel conducted a retrospective observational study comparing various vaccinated groups with the mRNA Comiranty (BNT162b2) produced by Pfizer-BioNTech.

Israel's rapid rollout of its COVID-19 vaccination campaign empowered these researchers to investigate the risk for additional virus infection – either a breakthrough infection in vaccinated individuals or reinfection in previously infected ones – over a more extended period than thus far described.

The findings from a non-peer-reviewed study published on October 25, 2021, demonstrated that natural immunity affords longer-lasting and stronger protection against infection, symptomatic disease, and hospitalization due to the Delta variant of SARS-CoV-2 coronavirus, compared to the BNT162b2 two-dose vaccine-induced immunity.

Notably, individuals who were previously infected with SARS-CoV-2 and given a single dose of the Comirnaty vaccine gained additional protection against the Delta variant.

However, protection provided by a third dose, administered in Israel since late July 2021, remains unknown, stated these researchers.

Specifically, this analysis demonstrates that SARS-CoV-2-naïve vaccinees had a 13.06-fold increased risk for breakthrough infection (fully-vaccinated people) with the Delta variant than those previously infected when the first event (infection or vaccination) occurred during January and February of 2021.

The increased risk was significant for symptomatic disease as well.

Broadening the research question to examine the extent of the phenomenon, they allowed the infection to occur between March 2020 to February 2021, when different virus variants were dominant in Israel, compared to vaccination only in January and February 2021.

Although the analysis results suggest waning natural immunity against the Delta variant, those vaccinated are still at a 5.96-fold increased risk for breakthrough infection.

And at a 7.13-fold increased risk for symptomatic disease compared to those previously infected.

However, SARS-CoV-2-naïve vaccinees were also at a greater risk for COVID-19-related-hospitalization compared to those previously infected.

'The advantageous protection afforded by natural immunity that this analysis demonstrates could be explained by the more extensive immune response to the SARS-CoV-2 proteins than that generated by the anti-spike protein immune activation conferred by the vaccine.' 

'However, as a correlate of protection, including the role of B-Cell and T-cell immunity, this concept remains a hypothesis,' said these researchers.

This study had several limitations; there was no external funding for the project.; the authors declare they have no conflict of interest.

Furthermore, the study from Israel contrasts with the U.S. CDC's Morbidity and Mortality Weekly Report issued on October 29, 2021.

This multistate analysis of hospitalizations for COVID-19–like illness among adults aged ≥18 years during January–September 2021, in the U.S.

This study stated 'among COVID-19–like illness hospitalizations among adults aged ≥18 years whose previous infection or vaccination occurred 90–179 days earlier, the adjusted odds of laboratory-confirmed COVID-19 among unvaccinated adults with previous SARS-CoV-2 infection were 5.49-fold higher than the odds among fully vaccinated recipients of an mRNA COVID-19 vaccine who had no previous documented infection (95% confidence interval = 2.75–10.99).'

And these researchers added, 'This report focused on the early protection from infection-induced and vaccine-induced immunity, though it is possible that estimates could be affected by time.'

'Understanding infection-induced and vaccine-induced immunity over time is important, particularly for future studies to consider.'