Introduction: To assess whether vaccination against SARS CoV2 in kidney transplant patients has had an effect in reducing mortality and the severity of coronavirus infection.

Methods: All kidney transplant patients diagnosed with COVID 19 in follow-up by our unit between March 2020 and February 28, 2022 were considered. Severity and mortality from COVID 19 were evaluated according to whether they had received or not vaccination against SARS CoV2 and also if they received one, two or three doses. The severity of the cases was classified as mild (outpatient management) or severe (hospitalization in a critical unit or death of the patient). Only a small percentage received RNA-type vaccines and a single dose, in combination with others. Age, sex, time since transplantation, time on dialysis of affected patients were analyzed, analysis was performed using Student's test or Chi square, as appropriate. A value of p<0.05 was considered significant.

Results: Between March 2020 and February 28, 2022, 195 cases of COVID 19 were diagnosed. As of November 2021, a third dose of vaccine was available. No significant differences were observed between the groups regarding age, time on dialysis, female gender, or time since transplant (Table 1). A numerical decrease in mortality was observed depending on whether or not they had received any dose of vaccine, greater in the group that received three doses over those who did not receive any, but statistical significance was not reached (p 0.08). Regarding severity, a higher proportion of mild cases was observed in those who received two and three doses than those who did not receive any (Dep value 0.02) and 0.006 respectively). Given the heterogeneity of the vaccination schedules that included a combination of inactivated virus vaccines (Sinopharm®), DNA vaccines (Astra Zeneca® and Gamaleya ®) and RNA vaccines (Pfizer®, Moderna®) and the small number of patients, no was able to discriminate efficacy according to the type of vaccine received.

Conclusion: In the group of patients who contracted COVID 19 and had received three doses of vaccine, a 50% reduction in mortality was observed, although it did not reach statistical significance, probably related to the low number of patients evaluated. Despite this, mortality in this group continues to be very high (14%). It must be taken into account that the patients with three doses who contracted the infection predominantly did so during the circulation phase of the Omicron strain, which is probably less aggressive. A significant increase was observed in the proportion of mild cases among those patients who had received at least two doses of the vaccine. Given the marked heterogeneity of vaccination schedules in our country, added to the small number of cases in each group, no conclusions could be drawn regarding the different types of vaccines available. These results encourage to vaccinate this group of patients and to evaluate the need for a fourth dose.