Long-term outcomes of COVID-19 vaccination in patients with rare and complex connective tissue diseases: The ERN-ReCONNET VACCINATE study.

Background: Vaccination is one of the most important measures to contain the COVID-19 pandemic, especially for frail patients. VACCINATE is a multicentre prospective observational study promoted by the European Reference Network on Rare and Complex Connective Tissue and Musculoskeletal Diseases (ERN ReCONNET) aimed at assessing the long-term outcomes of COVID-19 vaccination in patients with rare and complex connective tissue diseases (rcCTDs) in terms of efficacy and safety.

Methods: Adult rcCTDs patients were eligible for recruitment. Demographic, clinical and vaccination data were collected at enrolment. Follow-up visits were scheduled 4, 12, 24, 36 and 48 weeks after completion of the first vaccination cycle; data on adverse events, disease exacerbations and the occurrence of new SARS-CoV-2 infections were collected at these time-points.

Findings: 365 rcCTDs patients (87 % female, mean age 51.8 ± 14.6 years) were recruited. Overall, 200 patients (54.8 %) experienced at least one adverse event, generally mild and in most cases occurring early after the vaccination. During follow-up, 55 disease exacerbations were recorded in 39 patients (10.7 %), distributed over the entire observation period, although most frequently within 4 weeks after completion of the vaccination cycle. The incidence of new SARS-CoV-2 infections was 8.9 per 1000 person-months, with no cases within 12 weeks from vaccine administration and an increasing trend of infections moving away from the primary vaccination cycle. Only one case of severe COVID-19 was reported during the study period.

Interpretation: COVID-19 vaccination seems effective and safe in rcCTDs patients. The rate of new infections was rather low and serious infections were uncommon in our cohort. No increased risk of disease flares was observed compared to previous disease history; however, such exacerbations may be potentially severe, emphasising the need for close monitoring of our patients.