The ASX touched its highest level since mid-November today, taking confidence as the S&P 500 set a closing record on optimism around hospitalisation data relating to the Omicron variant. CSL led gains across the health sector, while resources stocks also stood out, with Pilbara setting an all-time high.

Which shares excelled?

Hitting a record high this week, Australian Clinical Labs (ASX: ACL) enjoyed a stellar showing, with the stock advancing 18%. The company, which is involved in pathology services, upgraded its first-half revenue for FY22 to between $497.3 million and $517.2 million, while also boosting net profit after tax to between $116.3 million and $128 million. Significant COVID testing numbers out of Victoria and New South Wales have acted as a catalyst for Australian Clinical Labs, a tailwind that also sparked a rally in shares of Sonic Healthcare (ASX: SHL) this week. There are growing expectations that the Omicron variant, and any new variants, will continue to drive testing revenue for these firms into the rest of the financial year.Meanwhile, takeover news gave a lift to superannuation services firm Link Administration (ASX: LNK) and property conveyancing business PEXA Group (ASX: PXA). After months of wrangling with another takeover bid, Link has confirmed it has entered into a Scheme Implementation Deed with Dye & Durham, which is proposing to acquire 100% of the company shares at $5.50 per share, plus a 3 cents per share interim dividend. The deal will provide Dye & Durham exposure to a 43% stake in PEXA Group, as it is partly owned by Link.Rising iron ore prices also provided an impetus for stocks from the iron ore sector over recent trading sessions. While Fortescue Metals Group (ASX: FMG) hit a three-month high, it was the likes of Mineral Resources (ASX: MIN) and Champion Iron (ASX: CIA) that led the gains. The price of iron ore climbed above US$125 per tonne this week, posting five weekly gains and touching its highest level in around two months on growing hopes of a recovery in steel demand in China.Buyers returned to pick up CSL (ASX: CSL) shares over recent trading sessions, with the biotech giant having a bumper week. The stock has retraced most of its losses following the announcement of its capital raise to acquire Swiss-based drug-maker Vifor. It was part of a broader rally in healthcare names this week, with investors increasingly expecting testing, vaccines and therapeutics to guide a transition' out of the pandemic.This week other top-performers included Appen (ASX: APX), Mincor Resources (ASX: MCR), Polynovo (ASX: PNV), as well as lithium miners Allkem (ASX: AKE) and Pilbara Minerals (ASX: PLS).

Which shares dragged on the market?

Despite paring some of its losses late in the week, Magellan Financial Group (ASX: MFG) was under fire this week when it announced the loss of a key mandate on Monday. In a filing with the ASX, Magellan said its fully-owned subsidiary, Magellan Asset Management, received notice from UK fund manager St James Place that it is terminating its mandate with Magellan. It is estimated the mandate represents approximately 12% of the Group current annual revenue.Elsewhere, there was a pullback in aspiring zero-carbon lithium producer Vulcan Energy Resources (ASX: VUL). While the company has enjoyed a standout performance in 2021, delivering significant returns to shareholders, it is now down more than one-third from its high. In an ASX release this week, substantial shareholder Gina Rinehart indicated she recently sold some of her holdings in the stock. Although she holds more shares than when she first bought into the company, thanks to participation in a capital raise months back, shareholders may have raised an eyebrow following her decision to offload a portion of her holdings just a couple weeks after a short report was published.Two favourites among retail investors, Imugene (ASX: IMU) and Brainchip (ASX: BRN), also slipped this week. Neither company released any price-sensitive news this week, suggesting profit taking and technical trading may have been driving some of the action in these popular names.Shares in Australian dairy manufacturer Bega Cheese (ASX: BGA) dived yesterday as the company pointed to a weak outlook. Management expects a number of issues to weigh on earnings this financial year. These include extensive and significant ranging from market disruption in Australian food service channels as a result of lockdowns, structural change in the Chinese infant and toddler dairy nutritional market, significant operational disruption including factory shutdowns, major changes to operations and logistics scheduling, increased safety and testing regimes, major cost increases and shortages across the entire supply chain.Another name caught up in some unfortunate news this week was Cimic Group (ASX: CIM). The construction firm was the subject of media reports regarding alleged missed payments to former staff, and doubts were raised around the sale of its joint venture in the Middle East. However, the company disputed the context around the claims, pointing to US$7 million it set aside for the acquiring party of the JV to settle outstanding wage obligations, and that it has no more financial exposure to the region.