Pos0544 the contribution of the 3rd and 4th booster bnt162b2 mrna vaccines to prevent severe covid-19 among autoimmune inflammatory rheumatoid diseases (aird) patients during the omicron outbreaks

Background The 3 rd booster of mRNA vaccines against SARS COV2 was highly efficient against delta variant but data regarding the efficacy of the 3 rd and 4 th boosters against the omicron variants, among AIRD pts are scarce. Objectives We aimed to assess the effect of the 3 rd and 4 th booster mRNA vaccines against SARS CoV2, in preventing severe COVID-19, in AIRD patients (pts) treated with immunomodulating drugs. Methods 212 pts (mean age(SD) 57(13), disease duration 11.2(7.4), who received the 3 rd booster (Pfizer) were included in the study. We performed serology tests 24 weeks after the second dose of vaccine and 4-8 weeks after the 3 rd booster. IgG Antibodies (Ab) against SARS COV2 virus were detected using the SARS-Cov-2 IgG II Quant (Abbott) assay. The test was considered positive above 50 AU/ml. Data regarding COVID-19 infection during the 5 th outbreak (omicron) were collected from the medical files. The length of observation period was defined as the time from the 3 rd booster to the last hospital visit or COVID 19 diagnosis, whichever occurred first. Results The 3 rd booster administration (Pfizer) significantly augmented the humoral response (from mean(SD) 1121(4723) AU/ml to 12153(13687)). 58 patients received the 4 th booster and 18 the 5 th booster. COVID-19 was diagnosed in 103 pts (49%) within mean(SD) 224.8(106.5) days after the 3 rd booster vaccination. 109 pts remained free of disease during mean(SD) follow-up 230.6(133.9). Following the 4 th booster, 26 (45%) out of 58pts contracted COVID-19 within mean(SD) 97.6(78.7) days after the vaccination. One 70 year old patient (vaccinated 3 times) died and 2 other pts (rituximab treated) had severe COVID-19. The IgG Ab titer after the 3 rd booster was lower in pts who contracted COVID 19 compared to those uninfected (mean(SD), median 8777.9(11716.4),3475 AU/ml vs 15348.1(14649.1),10801, p=0.004). There were no statistically significant differences between the pts with COVID-19 and those without, regarding age, type of disease, treatment and humoral response 24 weeks after the 2 nd vaccination. Conclusion Despite an enhanced humoral response obtained after the 3rd booster, 49% of AIRD pts vaccinated with 3 doses and 45% of pts vaccinated with 4 doses had COVID-19 during the omicron outbreaks. Higher humoral response to the 3 rd booster was associated with a lower rate of COVID19. The booster vaccines conferred 99% protection against severe COVID-19. REFERENCES: NIL. Acknowledgements: NIL. Disclosure of Interests None Declared.