Heterologous booster vaccination with CoronaVac following prime vaccination with mRNA vaccine.

Objective: Despite the high vaccine efficacy of mRNA COVID-19 vaccines, there are individuals who developed excessive reactogenic and/or allergic responses after the first mRNA dose and were considered ineligible for further mRNA doses. CoronaVac, an inactivated SARS-CoV-2 vaccine, is recommended in Singapore as an alternative.

Methods: Individuals, ineligible for further mRNA vaccines (BNT162b2 or mRNA-1273) because of excessive reactive responses to prime mRNA vaccination, were recruited and offered two doses of CoronaVac as booster vaccination 38-224 days post their mRNA vaccine dose.

Organ-specific immune response in lethal SARS-CoV-2 infection by deep spatial phenotyping.

Objectives: Immunopathology of ongoing COVID-19 global pandemic is not limited solely to pulmonary tissue, but is often associated with multi-organ complications, mechanisms of which are intensely being investigated. In this regard, the interplay between immune, stromal cells and cytokines in pulmonary and extrapulmonary infected tissues, especially in young adults (median age 46 years, range 30-53 years) without comorbidities, remains poorly characterised.

Methods: We profiled lung, heart and intestinal autopsy samples from five SARS-CoV-2-infected cases for 18-20 targets to detect immune, cytokine and stromal cell status at subcellular resolution by a novel IHC-based deep-phenotyping technique, iSPOT (immunoSpatial histoPhenOmics using TSA-IHC), to assess spatial and functional patterns of immune response , in lethal COVID-19 infection.

Human neutralising antibodies elicited by SARS-CoV-2 non-D614G variants offer cross-protection against the SARS-CoV-2 D614G variant.

Objectives: The emergence of a SARS-CoV-2 variant with a point mutation in the spike (S) protein, D614G, has taken precedence over the original Wuhan isolate by May 2020. With an increased infection and transmission rate, it is imperative to determine whether antibodies induced against the D614 isolate may cross-neutralise against the G614 variant.

Methods: Antibody profiling against the SARS-CoV-2 S protein of the D614 variant by flow cytometry and assessment of neutralising antibody titres using pseudotyped lentiviruses expressing the SARS-CoV-2 S protein of either the D614 or G614 variant tagged with a luciferase reporter were performed on plasma samples from COVID-19 patients with known D614G status ( = 44 infected with D614,  = 6 infected with G614,  = 7 containing all other clades: O, S, L, V, G, GH or GR).

South-east Asian Zika virus strain linked to cluster of cases in Singapore, August 2016.

Zika virus (ZIKV) is an ongoing global public health emergency with 70 countries and territories reporting evidence of ZIKV transmission since 2015. On 27 August 2016, Singapore reported its first case of local ZIKV transmission and identified an ongoing cluster. Here, we report the genome sequences of ZIKV strains from two cases and find through phylogenetic analysis that these strains form an earlier branch distinct from the recent large outbreak in the Americas.

A new common mutation in the hemagglutinin of the 2009 (H1N1) influenza A virus.

As the 2009 (H1N1) influenza A virus continues evolving, most mutations appear geographically and temporally confined. However, the latest surveillance data suggests emergence of a new prominent mutation, E391K, in the hemagglutinin (HA) that is globally on the rise. Interestingly, when modelled in the context of the available HA crystal structure, this mutation could alter salt bridge patterns and stability in a region of the HA oligomerization interface that is important for membrane fusion and also a known antigenic site.