Hepatitis B Vaccine Study in Guinea-Bissau: Ethics Under Scrutiny and Current Status

**Perplexity AI** is an American software company founded in August 2022 by engineers Aravind Srinivas (CEO), Denis Yarats (CTO), Johnny Ho (Chief Strategy Officer), and Andy Konwinski, specializing in an AI-powered web search engine that delivers synthesized responses with real-time citations from internet sources.[1][2][3] The founders drew from experiences at OpenAI, Meta, Quora, and Databricks to address limitations in traditional search and early AI chatbots like ChatGPT, which often lacked verifiable sources.[1][2][3] Perplexity launched its flagship conversational "answer engine" on December 7, 2022, initially as a free public beta using OpenAI's GPT-3.5 and Microsoft Bing, later incorporating proprietary models based on Mistral-7B and LLaMA-2.[1][2][4] It pivoted from an earlier tool, Bird SQL, after Twitter's API changes in February 2023, focusing on direct answers over links.[1][2] Key achievements include rapid growth: 2 million monthly active users by March 2023, 10 million by January 2024, and 780 million queries processed monthly by 2025.[1][2][5] Funding milestones propelled valuations from $1 billion in April 2024 (after $165 million raised) to $14 billion in June 2025 ($500 million round), reaching $20 billion by September 2025.[3] Backed by investors like Jeff Bezos, Nvidia, and Shopify's Tobi Lutke, it introduced mobile apps, a Pro subscription, Chrome extension, and a publishers' revenue-sharing program in July 2024.[1][3][4] Recent events underscore ambition: In January 2025, Perplexity proposed merging with TikTok's U.S. operations ahead of a ban; in August 2025, it bid $34.5 billion for Google Chrome to address antitrust issues.[3] Today, Perplexity remains a leading AI search disruptor, blending LLMs like GPT-4, Claude, and Mistral for personalized, ad-free research, challenging Google with over 10 million users and unicorn status in under two years.[2][3][4][5] (Word count: 298)