** Brokerage Mizuho believes while U.S. health insurers and clinical laboratories are poised for strong earnings growth in Q4 and 2022, hospitals could face certain challenges

** Reaffirms Anthem Inc Labcorp, IQVIA Holdings, CVS Health Corp and Universal Health Services as 2022 top picks

** Says while the Omicron variant has driven a surge in cases since November, severity has been lower than previous waves; expects increases in COVID-19 costs to be offset by a deferral in elective medical procedures

** Views 2022 as a recovery year for health insurers; any risks due to COVID-19 have been factored into the initial guidance provided by the sector

** The hospital sector has benefited so far from the surge in COVID-19 cases as well as patients with severe disease requiring costlier care, however, those trends were not as elevated in Q4, says brokerage

** Expect hospitals to meet estimates, rather than post beats throughout the pandemic - brokerage

** Mizuho expects clinical laboratories Labcorp and Quest Diagnostics to see a boost from COVID-19 testing, expects them to beat its Q4 testing estimates

** Strong growth in 2022 likely for contract research organizations given backlog, demand for new treatments, record funding levels and COVID-19 opportunities - brokerage

(Reporting by Amruta Khandekar) ((Amruta.Khandekar@thomsonreuters.com;))