Humoral Immune Response to COVID-19 Vaccines in Multiple Sclerosis Patients

A total of 126 volunteers with clinically definite relapsing-remitting MS and 52 healthy volunteers (HC) signed up for the study. Blood samples were collected from MS volunteers upon request from the Neuroimmunology department at The Cyprus Institute of Neurology and Genetics. The average number of days from the second dose to the booster dose was 90 days as indicated by the Ministry of Health in Cyprus. Throughout the study, patients that had COVID confirmed with PCR testing were excluded. In more detail, the inclusion criteria were: (1) patients above 18 years of age; (2) patients with clinically definite multiple sclerosis (CDMS) with clear clinical course of relapsing-remitting; (3) patients not experiencing any relapse symptoms during blood collection; (4) availability of a detailed clinical history [age of onset, disease duration calculated as the duration between sample acquisition and age of onset, Expanded Disability Status Scale (EDSS) score obtained on the day of sample acquisition, and treatments received]; and (5) being born in Cyprus and have resided in Cyprus from birth to at least early adult life. Exclusion criteria were: (1) presence of relapse in the 30 days before enrolment in the study; (2) inability or unwillingness to provide informed consent; (3) a history of alcohol or drug abuse; (4) pregnancy; and (5) history of previous SARS-CoV-2 infection. The inclusion and exclusion criteria, that are not solely MS-related, can be similarly extended to the healthy control group, save for the addition of an exclusion criterion that an individual may have any neurodegenerative, autoimmune, or underlying health issues. Table 1 shows the demographic details and clinical characteristics (EDSS, diseases duration, treatment at time of blood collection) of the MS volunteers and HCs. Other relevant data collected included SARS-CoV-2 infection history and lymphocyte counts for MS volunteers receiving fingolimod.
The timing of vaccinations followed the guidelines set by the EMA and the protocol set by the Ministry of Health in Cyprus, where the second dose was administered 3 weeks after the initial dose of BNT162b2 and the booster dose administered 3 months after the second dose. Blood samples were collected from all volunteers 3 months after the second vaccination dose. Reviewing preliminary results warranted additional analysis from a select MS group, as such MS volunteers receiving fingolimod were asked to return for another blood sample at least 2 weeks after receiving the booster dose. Note that due to the volunteering nature of the study, some volunteers were not willing to further donate blood. Additionally, due to volunteers getting infected with SARS-CoV-2 during the time between vaccination doses, a follow-up sample was not suitable for the purpose of the study.
Blood samples were collected in tubes containing clotting activators at the COVID-19 sampling unit of The Cyprus Institute of Neurology and Genetics. Following blood collection, samples were centrifuged for 10 min at 500 × g at 20°C to obtain cell-free serum. Serum was stored at −20°C until analysis.