ASX Health August Winners: Only lucky ones come out on top as CSL sparks 13pc sector sell-off

• The S&P ASX 200 Health Care index fell 13.21% in August as a tough reporting season weighed on sector
• CSL had its biggest ever one day fall on August 19, down 17% following softer FY25 results and restructure plans
• Despite the broader sector’s August slump, select names managed to deliver strong, healthy returns 

Just as the ASX healthcare sector looked like it was catching a bid and on the road to recovery it sustained a massive setback in August as a tough reporting season weighed heavily.

The healthcare sector fell 13.21% to be the worst performing of the 11 ASX sectors for August and YTD, where it is now deep in red territory, down more than 11%. In comparison the S&P/ASX 200 rose 3.10% in August and is up 12.33% YTD.

The heavy sell off follows a stronger month in July where the ASX healthcare sector rose 9.05% to be the top performer sector.

CSL bleeds with biggest daily fall on record

The sector’s largest company, blood products and vaccine giant  CSL (ASX:CSL), led the sector lower in August. CSL haemorrhaged on August 19 with its biggest single-day fall on record — plunging 17% and wiping more than $20 billion from its value — before continuing to bleed through the month.

Investors took the scalpel to the company on its FY25 results, reacting to a softer than expected FY26 outlook, the planned demerger of its vaccine arm CSL Seqirus into a standalone ASX entity and a 15% workforce cut affecting around 3000 jobs.

“It was pretty wild considering the size of CSL,”  Morgans’ healthcare analyst Iain Wilkie told Stockhead.

“There appeared to be confidence concerns in the market but CSL remains a high quality name with the pull back creating a better risk reward profile for long-term holders.”

In a post-mortem of August reporting season Wilkie noted seven large and midcap health stocks going up on their results. Nanosonics (ASX:NAN), Healius (ASX:HLS), Sigma Healthcare (ASX:SIG), PolyNovo (ASX:PNV), ProMedicus (ASX:PME) and ResMed (ASX:RMD) all delivered share price gains for investors.

On the flip side, seven large and mid cap healthcare stocks fell on their results including CSL, Cochlear (ASX:COH),  Healius (ASX:HLS), Monash IVF Group (ASX:MVF), Sonic Healthcare (ASX:SHL), Ramsay Health Care (ASX:RHC), EBOS Group (ASX:EBO) and Clinuvel Pharmaceuticals (ASX:CUV).

Despite an even split between winners and losers, Wilkie said the swings were dramatic, underscoring the unpredictable nature of the market on the day.

“Generally, the stocks were trading up in the one month prior to results,” Wilkie said.

“Of the stocks that went down significantly, the only one which has reversed its fortune was Healius, which fell 14% on the day of its results but has come back 23%.”

Wilkie said investors seemed to be short-term focused with a lot of the health care names, which presented long-term buying opportunities.

“Any effort required was put into the too hard basket with investors moving onto something else in the meanwhile with a pretty short-term focus,” Wilkie said.

“Long-term the thematics aren’t broken and healthcare will always be needed,” Wilkie said.

“There’s a growing ageing population and as you age more complications come up and healthcare is even more in demand so it’s never going away and probably one of the safest long-term bets you can make.”

How ASX biotechs performed in August

Despite the broader sector’s August slump, select names managed to deliver strong, healthy returns. Lung imager 4D Medical (ASX:4DX) was up 142.6% in August. At the end of July 4D Medical announced it had received a $10 million investment from large cap US-focused radiology imaging house ProMedicus (ASX:PME).

The company said the strategic investment would provide it with the growth capital to accelerate its commercial pipeline for existing products while advancing its ventilation perfusion imaging device CT:VQ towards regulatory clearance in the US.

Artrya (ASX:AYA) rose 107% in August after receiving US Food and Drug Administration (FDA) approval for its AI-powered Salix Coronary Plaque (SCP) module, for the “near real time, point of care assessment and management of coronary artery disease”.

Artrya submitted its 510(k) application on June 16 with an unusually swift response from the US regulator. Artrya’s SCP provides a detailed coronary plaque assessment in under 10 minutes and integrates with the FDA-cleared Salix Coronary Anatomy (SCA) platform, which analyses CT scans, offering faster, more actionable insights.

Rhythm Biosciences (ASX:RHY) was up  27.9% in August after a month of positive news flow including validation of its second-generation ColoSTAT blood test, showing it detects colorectal cancer consistently across all stages of the disease.

The medical diagnostics company also announced it was undertaking a capital raise of up to $3.75 million to advance the commercialisation of ColoSTAT, along with geneTYPE genetic risk assessment.

In further good news in August, Rhythm entered a co-marketing deal with leading global non-profit organisation Know Your Lemons Foundation (KYL), which is dedicated to breast cancer education and early detection. Under the deal Rhythm’s geneType Breast Cancer Risk Assessment Test will be promoted through a platform provided for employees of partner companies.

Infection control company Nanosonics (ASX:NAN) surged 10.6% in August following a stronger-than-expected FY25 result and FDA clearance for next-generation versions of its medical probe steriliser, Trophon.

The approval clears the way for the launch of Trophon 3 and a software upgrade for existing Trophon 2 users, called Trophon 2 Plus.

Revenue grew 17% to $198.6 million in FY25, driven by strong growth in consumables and capital sales. Capital sales rose 9% year-on-year, with upgrades up 10%. Gross profit margin reached 78.2%, up from 77.9% in FY24, reflecting what Wilkie described as “margin resilience despite tariff headwinds.”

Additionally, Nanosonics received FDA de novo clearance for its Coris device in FY25—the world’s first automated system designed specifically to clean the internal channels of flexible endoscopes.

 At Stockhead, we tell it like it is. While Rhythm Biosciens is a Stockhead advertiser, it did not sponsor this article.

This article does not constitute financial product advice. You should consider obtaining independent advice before making any financial decisions.