Yes good point, this is early work but definitely a necessary step toward answering an important question.

It's important to note the tremendous amount of evidence from a wide body of peer-reviewed literature which supports the fact that immunity acquired through natural infection provides protection against reinfection that is at least equally effective as vaccination. This fact has been repeatedly demonstrated in multiple large scale and long term serological studies [1][2][3][4][5].

- A previous history of SARS-CoV-2 infection was associated with an 84% lower risk of infection, with median protective effect observed 7 months following primary infection. This time period is the minimum probable effect because seroconversions were not included. This study shows that previous infection with SARS-CoV-2 induces effective immunity to future infections in most individuals. [1] (N=25,661)

- The study results suggest that reinfections are rare events and patients who have recovered from COVID-19 have a lower risk of reinfection. Natural immunity to SARS-CoV-2 appears to confer a protective effect for at least a year, which is similar to the protection reported in recent vaccine studies. [3] (N=15,075)

- Reinfection is rare in the young and international population of Qatar. Natural infection appears to elicit strong protection against reinfection with an efficacy ~95% for at least seven months. [4] (N=192,967)

- The degree of protection (10-fold) associated with seropositivity appears to be comparable to that observed in the initial reports of the efficacy of mRNA vaccines in large clinical trials. [5] (N=3,257,478)

The OP is one of the first and largest scale studies to evaluate the risk of reinfection - in the context of the delta variant which is currently dominant in many countries around the world - by directly comparing naturally acquired immunity to vaccine-induced immunity.

> 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.

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

If the OP study holds up to peer-review (which it likely will), then we can expect further studies attempting to replicate this finding, and even more studies attempting to explain why naturally acquired immunity induces a more robust immune response. The findings from those studies will be leveraged in the design of future vaccines - so these results will be a win just about any way you look at them.

[1] SARS-CoV-2 infection rates of antibody-positive compared with antibody-negative health-care workers in England: a large, multicentre, prospective cohort study (SIREN)
https://pubmed.ncbi.nlm.nih.gov/33844963/

[2] Risk of Reinfection After Seroconversion to Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2): A Population-based Propensity-score Matched Cohort Study
https://academic.oup.com/cid/advance-article/doi/10.1093/cid...

[3] Assessment of SARS-CoV-2 Reinfection 1 Year After Primary Infection in a Population in Lombardy, Italy
https://jamanetwork.com/journals/jamainternalmedicine/fullar...

[4] SARS-CoV-2 antibody-positivity protects against reinfection for at least seven months with 95% efficacy
https://www.sciencedirect.com/science/article/pii/S258953702...

[5] Association of SARS-CoV-2 Seropositive Antibody Test With Risk of Future Infection
https://jamanetwork.com/journals/jamainternalmedicine/fullar...