It should be noted... a strong natural immune systems will not likely produce long lasting antibodies. Persistent antibodies are associated with high risk co morbidities and disease severity.
If you are healthy you may not have needed persistent antibodies.
https://www.thelancet.com/journals/lanmic/article/PIIS2666-5247(21)00025-2/fulltext
We observed a distinct stepwise progression from the negative group to the persistent group, whereby patients with persistent antibodies were older and had more comorbidities, including hypertension and diabetes mellitus.
The demographic differences we observed were probably related to increased disease severity, as patients in the persistent group had poorer clinical outcomes, including pneumonia, supplemental oxygen requirement, intensive care unit admission, and mechanical ventilation. Baseline symptoms and investigations reflected this increased disease severity, with a greater proportion of patients with fever, cough, dyspnoea, reduced lymphocyte count, increased C-reactive protein, and increased lactate dehydrogenase in the persistent group. We observed a greater proportion of asymptomatic individuals in the negative group (11 [58%] of 19 patients) compared with the persistent group (three [6%] of 52 patients).
Viral load data, in the form of quantitative PCR results, were available for 70 patients and, in this subgroup, baseline earliest nasopharyngeal PCR cycle threshold values on admission were not associated with antibody response (data not shown), although there are limitations to this data as sample types varied (eg, nasopharyngeal swab, oropharyngeal swab, or sputum).
In the multivariable model that incorporated age, sex, and presence of comorbidities,
only disease severity was independently associated with persistent antibody levels, with an adjusted odds ratio of 5·20 (95% CI 1·83–16·7) for moderate disease severity and 30·3 (10·0–107·9) for severe disease severity, both compared with patients with mild disease (table 2).