ABSTRACT
The humoral immune response plays a key role in protecting the population from SARS-CoV-2 transmission. Patients who recovered from COVID-19 as well as fully vaccinated individuals have elevated levels of antibodies. The dynamic levels of the classes and subclasses of antibody responses to new variants that occur in different populations remain unclear. We prospectively recruited 60 participants, including COVID-19 patients and CoronaVac-vaccinated individuals, in Thailand from May to August 2021. Plasma samples were collected on day 0, day 14, and day 28 to determine the dynamic levels of the classes and subclasses of plasma antibodies against the receptor-binding domain (RBD) in the spike protein (S) of four SARS-CoV-2 strains (Wuhan, Alpha, Delta, and Omicron) via enzyme-linked immunosorbent assay. Our results indicated that the patients with SARS-CoV-2 infections had broader class and subclass profiles as well as higher levels of anti-S RBD antibodies to the Wuhan, Alpha, and Delta strains than did the CoronaVac-vaccinated individuals. The median antibody levels increased and subsequently declined in a month in the COVID-19 patients and in the vaccinated group. Correlations of the classes and subclasses of antibodies were observed in the COVID-19 patients but not in the vaccinated individuals. The levels of all of the anti-S RBD antibodies against the Omicron variant were low in the patients and in the vaccinated individuals. Our study revealed distinct antibody profiles between the two cohorts, suggesting different pathways of immune activation. This could have an impact on protection from infections by new variants of concern (VOC). IMPORTANCE The antibody responses to new SARS-CoV-2 variants that occur in different populations remain unclear. In this study, we recruited 60 participants, including COVID-19 patients and CoronaVac-vaccinated individuals, in Thailand and determined the dynamic levels of the IgG, IgA, IgM, and IgG subclasses of antibodies against the spike protein (S) of four SARS-CoV-2 strains. Our results showed that the patients with SARS-CoV-2 infections had broader profiles and higher levels of antibodies to the Wuhan, Alpha, and Delta strains than did the CoronaVac-vaccinated individuals. The antibody levels of both groups increased and subsequently decreased within 1 month. Higher and functional correlations of these antibodies were observed in the COVID-19 patients. The levels of all anti-S RBD antibodies against the Omicron variant were low in patients and vaccinated individuals. Our study revealed distinct antibody responses between the two groups, suggesting different pathways of immune response, which may have an impact on protection from infections by new SARS-CoV-2 variants.
Subject(s)
COVID-19 , SARS-CoV-2 , Humans , COVID-19/prevention & control , Antibody Formation , Thailand , Spike Glycoprotein, Coronavirus , Immunoglobulin G , VaccinationABSTRACT
Prior to the COVID-19 pandemic, there was a rapid increase in international travel. Travel medicine is a branch of preventive medicine focusing on risk assessment pre-travel, during travel and post-travel with the aim of promoting health and preventing adverse health outcomes. Travel medicine specialists inform travelers about potential health risks and mitigate infectious disease risks such as travelers' diarrhea, yellow fever, and malaria. Travel medicine topics were popular in the American Society of Tropical Medicine and Hygiene conferences between 2016 and 2020, and now comprise approximately 2% of all presentations. Most topics related to the post-travel assessment (44%), followed by diseases contracted during travel (24%), and pre-travel assessment and consultation (23%). Our analysis of the 10 sub-domains of travel medicine issues found that malaria (26%) and immunization (12%) were represented to the greatest extent. We anticipate that both travel and tropical medicine fields will regain their popularity after recovery from the pandemic.