Effectiveness of full mRNA vaccinations to prevent COVID-19 among immunocompromised patients receiving tixagevimab-cilgavimab as pre-exposure prophylaxis

Pre-exposure prophylaxis with monoclonal antibodies (mAbs) offers protection against COVID-19 in immunocompromised patients. To attest full vaccinations, defined by ≥ 3-dose mRNA vaccines, providing additional protection effect on mAbs against COVID-19, we retrospectively compared the breakthrough SARS-CoV-2 infection rates between adult immunocompromised patients with and without full vaccinations before receiving prophylactic tixagevimab-cilgavimab during the Omicron BA.5 dominant period. Among 148 patients, most (96.6 %) had hematologic malignancies. Fifty-nine (39.9 %) patients received full vaccinations before tixagevimab-cilgavimab. Overall, 19 (12.8 %) patients have breakthrough infections, and only three of them had full vaccinations. By a multivariable logistic regression model, receipt of full vaccinations was the only independent factor associated with prevention of breakthrough infections (adjusted odds ratio, 0.26 [95 % CI, 0.07-0.95]). The Kaplan-Meier estimate showed a lesser trend of breakthrough infections with those receiving full vaccinations (P = 0.08). Our study underscores the importance of full vaccinations among immunocompromised patients receiving pre-exposure prophylactic mAbs against COVID-19.