Reading an Israeli study... not sure if it is the one Karl is referencing:

"Comparing effectiveness across age groups, we find that although vaccine effectiveness is relatively similar for age groups between 16-80 years old, a statistically significant lower effectiveness is observed for older patients, the study says. We also find that specific chronic comorbidities, including high blood pressure, COPD, immunosuppression and type 2 diabetes, are negatively associated with vaccine efficacy. These results add to previous reports regarding lower vaccine effectiveness for diabetic patients and patients with multiple coexisting conditions, the authors add."