Impact of various vaccine boosters on neutralization against Omicron following prime vaccinations with inactivated or adenovirus-vectored vaccine (preprint)

Since the first report on November 24, 2021, the Omicron SARS-CoV-2 variant is now overwhelmingly spreading across the world. Two SARS-CoV-2 inactivated vaccines (IAVs), one recombinant protein subunit vaccine (PRV), and one adenovirus-vectored vaccine (AdV) have been widely administrated in many countries including China to pursue herd immunity. Here we investigated cross-neutralizing activities in 341 human serum specimens elicited by full-course vaccinations with IAV, PRV and AdV, and by various vaccine boosters following prime IAV and AdV vaccinations. We found that all types of vaccines induced significantly lower neutralizing antibody titers against the Omicron variant than against the prototype strain. For prime vaccinations with IAV and AdV, heterologous boosters with AdV and PRV, respectively, elevated serum Omicron-neutralizing activities to the highest degrees. In a mouse model, we further demonstrated that among a series of variant-derived RBD-encoding mRNA vaccine boosters, it is only the Omicron booster that significantly enhanced Omicron neutralizing antibody titers compared with the prototype booster following a prime immunization with a prototype S-encoding mRNA vaccine candidate. In summary, our systematical investigations of various vaccine boosters inform potential booster administrations in the future to combat the Omicron variant.

Does Liquidity Management Induce Fragility in Treasury Prices: Evidence from Bond Mutual Funds (preprint)

Bond mutual funds holding illiquid assets (e.g., corporate bonds) actively manage their positions in Treasuries to buffer redemption shocks. We argue and show supporting evidence that this liquidity management practice can induce fragility in Treasury prices. We find that Treasury pairs commonly held by bond funds exhibit higher return comovement than pairs with little fund common ownership. This effect is more pronounced during downside markets or when funds experience large outflows, but is weak for corporate bond pairs. We address endogeneity concerns by exploiting two plausibly exogenous events: the outbreak of COVID-19 and the 2003 mutual fund scandal.