Vaccination was found to be more immunogenic (around 40 and 5 times in IgG and IgA antibody classes, respectively) than illness which is consistent with earlier reports [20,35,37,38]

Vaccination was found to be more immunogenic (around 40 and 5 times in IgG and IgA antibody classes, respectively) than illness which is consistent with earlier reports [20,35,37,38]. may have contributed to breakthrough infections. Although they caused seroconversion similar to the booster, antibody levels in such patients fell more rapidly than after re-vaccination. On the other hand, in individuals who did not receive booster(s) and who did not present breakthrough infection, anti-SARS-CoV-2 antibodies returned to pre-vaccination levels after 20 months. The most commonly recognized adverse effects were injection site redness and swelling. Conclusion: Vaccination is Cefuroxime axetil highly effective in preventing the most severe outcomes of COVID-19 and should be performed regardless of prior infection. Booster doses significantly enhance anti-SARS-CoV-2 antibody levels and, in contrast to those obtained by breakthrough infection, they remain longer. Keywords: anti-SARS-CoV-2 antibody kinetics, breakthrough infections, COVID-19, mRNA Cefuroxime axetil vaccine, vaccine safety assessment 1. Introduction The global spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causing coronavirus disease 2019 (COVID-19) resulted in pandemic status for the illness by the World Health Organisation (WHO) [1]. Since the first identification of SARS-CoV-2 in December 2019, the WHO has recorded more than 770 million confirmed cases of COVID-19, including almost 7 million deaths [2]. Vaccination is one of the most effective and cost-efficient public health interventions to prevent infectious diseases [3]. There are several COVID-19 vaccines validated for use by the WHO. The mass vaccination programme started in early December 2020, and the number Cefuroxime axetil of vaccine doses currently administered worldwide is more than 13 billion [2,4]. The first COVID-19 vaccine recommended by the WHO was the BNT162b2 (Comirnaty?, Pfizer, Philadelphia, PA, USA and BioNTech, Mainz, Germany), which consists of a nucleoside-modified mRNA encoding spike (S) protein, specific to the Wuhan-Hu-1 strain isolated in China during the first outbreak in late 2019, formulated in lipid nanoparticles [4,5]. Transient expression of the S antigen Rabbit Polyclonal to STK10 induces neutralising antibodies and cellular immune responses providing defence from COVID-19 [5]. Data obtained from clinical trials have shown that a two-dose scheme of the vaccine, administered 21 days apart, offered 86% and 95% protection against infection and severe disease, respectively Cefuroxime axetil [4,6,7]. The emergence of SARS-CoV-2 mutants, carrying changes mainly in the S protein, led to increased transmission and/or infectivity of the virus and reduced vaccine efficacy, resulting in infections of vaccinated individuals [8,9,10,11]. In addition, several studies have shown that the antibody levels decline markedly in six months following primary vaccination, which may also contribute to an increase in breakthrough infections [12,13,14,15,16]. Booster doses were aimed at enhancing the immune response to provide long-term protection against COVID-19, including that caused by the variants of concern (VOCs) [6,7,16,17]. For Alpha, Beta, Gamma, and Delta variants, the effectiveness of the vaccine in preventing infection and severe disease remained similar as the assumed efficacy of the ancestral strain, while for Omicron sub-lineages (including BA.1, BA.2, BA.5) it amounts to 44% and 72%, respectively [7]. Furthermore, vaccination after recovery from SARS-CoV-2 infection resulting in a hybrid immunity was found to significantly increase the strength of the humoral response [7,18,19,20,21]. Vaccine effectiveness, in contrast to vaccine efficacy assessed in clinical trials, is based on a reduction in the risk of infection/disease among vaccinated individuals in real life. This can be influenced by many factors, including internal host factors (e.g., age, gender, genetics, co-morbidities), external host factors (e.g., pre-existing immunity, microbiota, past infections), environmental factors (e.g., geographical location, season, family size) and behavioural factors (e.g., smoking, alcohol consumption, exercise,.

﻿Vaccination was found to be more immunogenic (around 40 and 5 times in IgG and IgA antibody classes, respectively) than illness which is consistent with earlier reports [20,35,37,38]