Antibody response and the clinical presentation of patients with COVID-19 in Croatia: the importance of a two-step testing approach.

According to anti-SARS-CoV-2 seroresponse in patients with COVID-19 from Croatia, we emphasised the issue of different serological tests and need for combining diagnostic methods for COVID-19 diagnosis. Anti-SARS-CoV-2 IgA and IgG ELISA and IgM/IgG immunochromatographic assay (ICA) were used for testing 60 sera from 21 patients (6 with severe, 10 moderate, and 5 with mild disease). The main clinical, demographic, and haemato-biochemical data were analysed. The most common symptoms were cough (95.2%), fever (90.5%), and fatigue and shortness of breath (42.9%). Pulmonary opacities showed 76.2% of patients. Within the first 7 days of illness, seropositivity for ELISA IgA and IgG was 42.9% and 7.1%, and for ICA IgM and IgG 25% and 10.7%, respectively. From day 8 after onset, ELISA IgA and IgG seropositivity was 90.6% and 68.8%, and for ICA IgM and IgG 84.4% and 75%, respectively. In general, sensitivity for ELISA IgA and IgG was 68.3% and 40%, and for ICA IgM and IgG 56.7% and 45.0%, respectively. The anti-SARS-CoV-2 antibody distributions by each method were statistically different (ICA IgM vs. IgG, p = 0.016; ELISA IgG vs. IgA, p < 0.001). Antibody response in COVID-19 varies and depends on the time the serum is taken, on the severity of disease, and on the type of test used. IgM and IgA antibodies as early-stage disease markers are comparable, although they cannot replace each other. Simultaneous IgM/IgG/IgA anti-SARS-CoV-2 antibody testing followed by the confirmation of positive findings with another test in a two-tier testing is recommended.

Slower Waning of Anti-SARS-CoV-2 IgG Levels Six Months after the Booster Dose Compared to Primary Vaccination.

Anti-SARS-CoV-2 IgG titer decreases rapidly after primovaccination, leading to a mandatory booster vaccination. We analysed anti-SARS-CoV-2 Spike RBD IgG levels (positive ≥ 50 AU/mL) in 405 healthcare workers (3010 sera) who received a booster dose (BD) 9 months after two-dose BNT162b2 primovaccination. Median antibody titer at the time of BD (582.6 AU/mL) was 1.7-fold and 16.4-fold lower than the peak titer after the first (961.5 AU/mL) and the second vaccine dose (SVD) (10,232.6 AU/mL), respectively. One month after vaccination, IgG titer increased 40.6-fold after BD compared with a 10.8-fold increase after primovaccination. Three months after vaccination, post-booster antibodies decreased significantly slower (2.2-fold) than after primovaccination (3.3-fold). At six months, antibodies decreased slower after BD (4.5-fold; median 5556.0 AU/mL) than after primovaccination (9.6-fold; median 1038.5 AU/mL). Antibody titers before and one month after BD correlated weakly (r = 0.30) compared with a strong correlation (r = 0.65) between the corresponding post-primovaccination titers. Pre-vaccination COVID-19 had no effect on IgG levels after BD compared with a positive effect after primovaccination. Despite high post-booster IgG levels, 22.5% of participants contracted mild COVID-19. The trend of IgG decline indicates the need for further revaccination, but the vaccine type should be defined according to viral mutations.

Decline of Anti-SARS-CoV-2 IgG Antibody Levels 6 Months after Complete BNT162b2 Vaccination in Healthcare Workers to Levels Observed Following the First Vaccine Dose.

Research on post-vaccination antibody dynamics has become pivotal in estimating COVID-19 vaccine efficacy. We studied anti-SARS-CoV-2 Spike RBD IgG levels in 587 healthcare workers (2038 sera) who completed BNT162b2 vaccination. Average antibody titer 3 weeks after the first dose in COVID-19-naïve participants (median 873.5 AU/mL) was 18-fold higher than the test threshold, with a significant increase 1 month (median 9927.2 AU/mL) and an exponential decrease 3 (median 2976.7 AU/mL) and 6 (median 966.0 AU/mL) months after complete vaccination. Participants with a history of COVID-19 prior to vaccination showed significantly higher antibody levels, particularly after the first dose (median 14,280.2 AU/mL), with a slight decline 1 month (median 12,700.0 AU/mL) and an exponential decline in antibody titers 3 (median 4831.0 AU/mL) and 6 (median 1465.2 AU/mL) months after vaccination. Antibody levels of COVID-19-naïve subjects after the first dose were moderately correlated with age (r = -0.4). Multivariate analysis showed a strong independent correlation between IgG levels 6 months after vaccination and both IgG titers after the first dose and 1 month after vaccination (R2 = 0.709). Regardless of pre-vaccination COVID-19 history, IgG levels 6 months after vaccination were comparable to antibody levels reached by COVID-19-naïve participants after the first vaccine dose.

[Prevalence of hepatitis B and C among prison population in Croatia]. / Prevalencija hepatitisa B i C u zatvorskoj populaciji Hrvatske.

In 2007, incarcerated persons accounted for 0.41% (approximately 16,500) of the Croatian population. In the heterogeneous structure of the prison population in Croatia, some 25%-30% of the prisoners are drug abusers. In this study, we intended to determine precisely the structure of the prison population in Croatia and the prevalence of HBV and HCV markers in this population. It is well known that HBV and HCV infection can spread within prisons, and therefore we tried to determine the rate of acute HBV and HCV infection among prisoners in Croatian prisons. In total, 25.7% of prisoners were positive for some viral hepatitis markers (HBV 11.3%, HCV 8.3%, and HBV/HCV 6.3%). The rate of HBV infection was very high among intravenous drug users (26.2%) and relatively high among highly promiscuous individuals (19.9%). HCV infection was most prevalent among intravenous drug users (50.2%) and relatively high among highly promiscuous individuals (7.5%). HBV/HCV coinfection was recorded in 23.5% of prisoners. Acute infection with HBV was detected in 0.3% and with HCV in 1.2% of the study population. One fourth of all prisoners had contact with HBV, HCV, or both viruses. It is evident that both hepatitis virus infections (HCV more and HBV less) are spreading within prisons among prisoners. The opportunity of screening, testing, vaccination, treatment and education of high-risk individuals while they are in the controlled environment of a correctional facility is a good policy for both individuals and the community.

[Viral hepatitis. Croatian consensus conference--2009]. / Virusni hepatitis. Hrvatska konsenzus konferencija 2009.

Summarized text of Croatian Consensus Conference on Viral Hepatitis of 2009 comprises the following chapters: 1) Epidemiology, 2) Clinical Picture, 3) Diagnostic Procedure, 4) Aims of Treatment of Viral Hepatitis, 5) Terminology, 6) Medicaments (6.1. Interferon, 6.2. Analogues of Nucleozides and Nucleotides), 7) Hepatitis B (7.1. Serologic and Molecular HBV Diagnostics, 7.2. Terminology, 7.3.Whom to Treat? 7.4. Therapy), 8) Hepatitis C (8.1. Serologic and Molecular HCV Diagnostics, 8.2. Terminology, 8.3. Whom to Treat? 8.4. Therapy). Clinical, laboratory and histologic assessment of patients with chronic viral hepatitis (algorythm of pretherapeutic treatment; histologic evaluation) and notions related to therapy of viral hepatitis (category of the patient and category of the response to treatment) are presented in related tables.