Investigation of Nasal Mucosal IgA Responses in the Population Following COVID-19 Pandemic — China, September 2022–August 2023

What is already known about this topic?Mucosal IgA plays a crucial role in host immunity against respiratory viruses.Recent studies suggest that it has the potential to mitigate the transmission of the severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)Omicron variant.However,a comprehensive population-based analysis examining mucosal IgA levels following the winter 2022 wave of the coronavirus disease 2019(COVID-19)pandemic is yet to be conducted.What is added by this report?In our study involving 3,421 participants,we documented IgA responses subsequent to SARS-CoV-2 infection.A significant proportion of individuals sustained increased levels of IgA for over six months.These levels were also observed in individuals with prior infections who underwent asymptomatic reinfections,indicating an active production of IgA antibodies.Further,individuals with multiple vaccinations or severe symptoms tended to display elevated IgA levels after recovery.What are the implications for public health practice?IgA in the nasal mucosa is crucial for defense against SARS-CoV-2 infection.These insights can enhance our knowledge of immune responses following infection and have provided certain reference values for disease prevention and control strategies.

Longitudinal Analysis of Antibody Dynamics in Severe Fever with Thrombocytopenia Syndrome Patients—High-Incidence Regions of China,2010–2023

What is already known about this topic?Severe fever with thrombocytopenia syndrome(SFTS)is a serious tick-borne disease in East Asia with high mortality,particularly affecting the elderly.Since its discovery in 2010,inconsistencies in small-scale studies and the lack of decade-long research on antibody levels in large population samples after natural infection,along with the absence of an effective vaccine,highlight the need for large-scale,long-term data in highincidence regions of China.What is added by this report?This study of 1,410 serum samples from SFTS patients in high-incidence regions of China reveals that immunoglobulin M(IgM)levels peak at 8–14 days post-infection,declining to nearly undetectable levels by 180 days.Immunoglobulin G(IgG)and neutralizing antibodies(NAb)levels peak at 22–180 days,persisting up to 10 years.IgM levels correlate with viral load and various immune and coagulation parameters,with lower levels observed in fatal cases.During convalescence,elderly patients have lower IgG levels,whereas females exhibit higher IgG levels compared with males.What are the implications for public health practice?The study’s findings on long-term antibody dynamics in SFTS patients can significantly improve vaccine development,optimize therapy scheduling,inform public health policies,and enhance diagnostic tools,leading to better disease management and prevention in high-incidence areas.