Testing for SARS-CoV-2: Can We Stop at 2?

The COVID-19 epidemic requires accurate identification and isolation of confirmed cases for effective control. This report describes the effectiveness of our testing strategy and highlights the importance of repeat testing in suspected cases in our cohort.

Serological response to trivalent inactivated influenza vaccine in HIV-infected adults in Singapore.

A cohort of 81 HIV-infected participants received seasonal trivalent inactivated influenza vaccine (TIV) and their humoral responses were monitored using hemagglutination inhibition (HAI) assay and enzyme-linked immunosorbent assay (ELISA). Three weeks after the vaccination, the percentage of the cohort that had an HAI titer of >1:40 was 35% (for H1N1), 43% (for H3N2) and 19% (for influenza B). An increase in HAI titer can be achieved by an increase in magnitude of the antibody responses, which can be measured by an increase in ELISA titer; as well as a quality improvement of the antibody responses through increased avidity to the virus. For some individuals, an increase in avidity alone is sufficient to reach the sero-protective titer. Notably, a number of volunteers showed an increase in ELISA titer without a rise in HAI titer. A total of 24 participants (30%) did not show any significant increase in both HAI and ELISA tests after vaccination. Apart from a lower peripheral CD4+ T cell count, the non responders' peripheral blood mononuclear cells (PBMC) also had a higher IL-10 mRNA expression after TIV vaccination ex vivo. Cytokine profiling demonstrated that, apart from a weaker MCP-1 expression in the non-responder group, PBMC from both groups responded comparably to lipopolysaccharide (LPS) stimulation in vitro. Since only 3 participants developed sero-protective titers against all 3 subtypes after vaccination, our study highlights a need to enhance the immunogenicity of the subunit vaccine for this population, potentially through harnessing the innate immunity with an external adjuvant.