A Wall Street quant chief breaks down why a COVID-19 vaccine is not the silver bullet investors have been hoping for — and warns another stock-market meltdown is likely

· Investors may be overestimating how quickly a successful COVID-19 vaccine can restore lost economic activity and company revenues, according to Andrew Lapthorne, the global head of quantitative research at Societe Generale.
· He says downside risks abound following the massive rally that has already occurred. 
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