P29: EFFECTS OF VACCINATION ON INCIDENCE AND OUTCOME OF SARS-COV-2 INFECTION IN PATIENTS WITH MONOCLONAL GAMMOPATHY OF UNDETERMINED SIGNIFICANCE (MGUS)
Authors: N Sgherza, R Rizzi, P Curci, D Roccotelli, M Croce, M Avantaggiato, L Ruga, P Musto
Journal: HemaSphere (2022)

We recently investigated incidence of SARS-CoV-2 infection and COVID-19 outcomes in MGUS patients during the early waves of pandemic, when vaccines were still not available (Sgherza N. et al. Haematologica. 2022). In that study, we found that these subjects neither have an increased risk of contracting SARS-CoV-2, nor show poorer COVID-19 outcomes with respect to controls. Aiming to specifically address the clinical effects of vaccines, we compared incidence and outcome of SARS-CoV-2 infection of 1,454 previously described, not vaccinated MGUS patients (91 of whom were SARS-CoV-2 positive), with those observed in a similar population during the national vaccination campaign. So far, we have obtained retrospective information from 41 individuals found to be SARS-CoV-2 positive among 763 MGUS patients analyzed after at least two doses of anti-SARS-CoV-2 vaccine received between April 2021, and January, 2022. The mean age of this group was 64.1 +/-14.1 years (range 31-90); 16 patients were female (39%), and 25 were male (61%). About MGUS-subtypes, the most frequent one was IgG-lambda (n=20; 48.8%), followed by IgG-kappa (n=14; 34.1%), IgA-kappa (n=3; 7.3%), IgA-lambda (n=2; 4.9%) and IgM-kappa (n=2; 4.9%). Most of patients (39/41, 95%) were at low or low-intermediate risk, according to Mayo Clinic prognostic model. Twenty-one (51.2%) patients developed SARS-CoV-2 infection after two doses (5, 15 and 1 patients receiving ChAdOx1-S, BNT162b2 mRNA and mRNA-1273 vaccines, respectively), twenty (48.8%) after three doses (BNT162b2 mRNA or mRNA-1273 as “booster” dose, repectively). The mean number of days between last dose of vaccine and SARS-CoV-2 infection was 98.8 +/-77.8 (range 2-240). The two populations of SARS-CoV2 positive MGUS patients (before and after vaccination) were comparable for age, sex and presence of co-morbidities (data not shown). Overall, rates of symptoms (59.3% vs 31.8%), hospitalization (20.9% vs 0%), and hospitalization in Intensive Care Unit (11% vs 0%) were significantly higher in still not vaccinated MGUS patients than in those who had received vaccines (Table 1). A strong trend toward a higher rate of deaths (8,8% vs 0%) was also observed in not vaccinated patients, although it did not reach statistical significance, probably due to the small number of evaluated patients. Interestingly, incidence of SARS-CoV-2 detection in vaccinated patients was not significally different from that of patients analyzed before vaccination (5.4% vs 6.2%, respectively) (p=0.402). Our data indicate that the possibility to be infected by SARS-CoV-2 is probably not significantly reduced by vaccination (even after three doses), likely also because of the higher diffusion capacity of the recently recognized Omicron viral variants. However, as observed in normal population and in other hematological contexts, the clinical outcome of COVID-19 may be significantly improved after vaccination in MGUS patients, with less of one third of patients who were symptomatic and no case of hospitalization or death in our series. These observation reinforces the need to proceed with an active vaccination program in these patients.