COVID-19 vaccination uptake in people with multiple sclerosis compared to the general population.

OBJECTIVE: To determine the COVID-19 vaccine uptake among people with multiple sclerosis (pwMS) compared to the general population in Croatia. METHODS: Data from all pwMS entered in the MS Base register until March 24th, 2022 were extracted including age, sex, MS phenotype, disease-modifying therapy (DMT), and date of COVID-19 vaccination. Data on the general population of Croatia were obtained from the vaccination register of the Croatian Institute of Public Health. RESULTS: 64.4% pwMS were fully COVID-19 vaccinated which was comparable to 66.3% of the general population. More pwMS were fully vaccinated in the age group 20-24 (74.1% vs 51.7%), and fewer pwMS were fully vaccinated in the age group 65-69 (33.3% vs 80.4%) compared to the general population of the same age group, respectively. PwMS who received at least one dose of any COVID-19 vaccine were older (40.5 vs 37.6 years, p = 0.01), had higher EDSS (2.0 vs 1.0, p = 0.025), and had longer disease duration (6.39 vs 5.35 years, p = 0.02), were more likely to have progressive disease course (p = 0.049) and were on high efficacy DMTs (p = 0.045) compared to unvaccinated pwMS. Longer disease duration positively predicted vaccine uptake. CONCLUSION: Croatia has suboptimal COVID-19 vaccination uptake without a significant difference between the general population and pwMS.

Seroprevalence of SARS-CoV-2 infection among children in Children's Hospital Zagreb during the initial and second wave of COVID-19 pandemic in Croatia.

INTRODUCTION: The study aimed to investigate the prevalence and titres of anti-SARS-CoV-2 antibodies in children treated at the Children's Hospital Zagreb in the first and the second wave of the COVID-19 pandemic. Statistical significance of difference at two time points was done to determine how restrictive epidemiological measures and exposure of children to COVID-19 infection affect this prevalence in different age groups. MATERIALS AND METHODS: At the first time point (13th to 29th May 2020), 240 samples and in second time point (24th October to 23rd November 2020), 308 serum samples were tested for anti-SARS-CoV-2 antibodies by enzyme-linked immunosorbent assay (ELISA) and electrochemiluminescence immunoassay (ECLIA). Confirmation of results and titre determination was done using virus micro-neutralization test. Subjects were divided according to gender, age and epidemiological history. RESULTS: Seroprevalence of anti-SARS-CoV-2 antibodies differs significantly in two time points (P = 0.010). In first time point 2.9% of seropositive children were determined and in second time point 8.4%. Statistically significant difference (P = 0.007) of seroprevalence between two time points was found only in a group of children aged 11-19 years. At the first time point, all seropositive children were asymptomatic with titre < 8. At the second time point, 69.2% seropositive children were asymptomatic with titre ≥ 8. CONCLUSIONS: The prevalence of anti-SARS-CoV-2 antibodies was significantly lower at the first time point than at the second time point. Values of virus micro-neutralization test showed that low titre in asymptomatic children was not protective at the first time point but in second time point all seropositive children had protective titre of anti-SARS-CoV-2 antibodies.

SARS-CoV-2 Seroprevalence and Neutralizing Antibody Response after the First and Second COVID-19 Pandemic Wave in Croatia.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a novel coronavirus with a pandemic spread. So far, a total of 349,910 SARS-CoV-2 cases and 7687 deaths were reported in Croatia. We analyzed the seroprevalence and neutralizing (NT) antibody response in the Croatian general population after the first (May-July 2020) and second (December 2020-February 2021) pandemic wave. Initial serological testing was performed using a commercial ELISA, with confirmation of reactive samples by a virus neutralization test (VNT). A significant difference in the overall seroprevalence rate was found after the first (ELISA 2.2%, VNT 0.2%) and second waves (ELISA 25.1%, VNT 18.7%). Seropositive individuals were detected in all age groups, with significant differences according to age. The lowest prevalence of NT antibodies was documented in the youngest (<10 years; 16.1%) and the oldest (60-69/70+ years; 16.0% and 12.8%, respectively) age groups. However, these age groups showed the highest median NT titers (32-64). In other groups, seropositivity varied from 19.3% to 21.5%. A significant weak positive correlation between binding antibody level as detected by ELISA and VNT titer (rho = 0.439, p < 0.001) was observed. SARS-CoV-2 NT antibody titers seem to be age-related, with the highest NT activity in children under 10 years and individuals above 50 years.