Medibank Private Ltd's stock plummeted 5.01% during intraday trading on Thursday, following the release of its half-year financial results for HY26.

The sharp decline came after the health insurer reported that net profit after tax attributable to shareholders fell 11.0% to AUD 302.9 million. While group revenue grew 5.5% to AUD 4.5 billion and operating profit increased 6.0% to AUD 381.7 million, the bottom line was impacted by a 17.1% decline in net investment income and AUD 15.0 million in non-recurring cybercrime costs related to the 2022 security breach.

Despite declaring a 6.4% higher interim dividend of 8.3 cents per share and reporting policyholder growth, investors reacted negatively to the profit decline and ongoing costs from the cyber incident. The company also noted that underlying NPAT decreased 0.3% to AUD 297.8 million, with Medibank Health segment showing stronger performance with profit growth of 28.5%.