* Pfizer up on lifting annual sales forecast for COVID-19 vaccine * CVS Health higher on raising 2021 profit outlook * Futures fall: Nasdaq 0.82%, Dow 0.40%, S&P 0.53% (Adds details; Updates prices throughout) May 4 (Reuters) - The Nasdaq index was set to open lower on Tuesday as investors continued to move out of megacap growth stocks and into companies that are expected to benefit from the reopening of economies. Highly valued technology companies including Microsoft Corp , Alphabet Inc, Apple Inc, Amazon.com Inc and Facebook Inc fell between 0.6% and 1.7% in premarket trading. U.S. and European stock markets also saw a sudden 0.5% drop in hefty volumes around 7:30 a.m. ET on Tuesday, leaving traders scratching their heads and one calling it a “micro flash crash”. Copious stimulus measures, speedy vaccination drives and the Federal Reserve’s accommodative policy stance have spurred a strong rebound in the U.S. economy and pushed Wall Street to record highs this year. The so-called “pandemic winners”, however, have recently started to fall out of favor. “While megacap tech companies have been a core part of the solid performance of portfolios throughout the pandemic, we think investors should be careful to avoid overallocation to this part of the market,” Mark Haefele, chief investment officer at UBS Global Wealth Management, wrote in a client note. “In an environment of accelerating growth, we continue to prefer cyclical and value sectors such as financials and energy.” Planemaker Boeing Co rose 0.2%, while oil major Chevron Corp gained 0.7%. At 8:38 a.m. ET, Dow e-minis were down 136 points, or 0.4%, S&P 500 e-minis were down 22.25 points, or 0.53%, and Nasdaq 100 e-minis were down 113 points, or 0.82%. Among other stocks, Pfizer Inc rose 1% as it raised its annual sales forecast for the COVID-19 vaccine it co-developed with Germany’s BioNTech SE. CVS Health Corp gained 1.7% on reporting first-quarter profit above analysts’ estimates and raising its 2021 profit forecast. Dupont edged 0.5% higher after the industrial materials maker raised its full-year profit and revenue forecasts and beat first-quarter expectations. First-quarter earnings have been largely upbeat. Average profits at S&P 500 companies are expected to have risen 46% in the quarter, compared with forecasts of a 24% growth at the start of April, according to IBES data from Refinitiv. Investors also awaited data through the week, including the Labor Department’s non-farm payrolls data, slated to be released on Friday. The report is expected to show a rise in job additions in April. (Reporting by Shreyashi Sanyal and Sruthi Shankar in Bengaluru; Editing by Saumyadeb Chakrabarty and Shounak Dasgupta) Our Standards: The Thomson Reuters Trust Principles.