Health Misinformation Act of 2021 This bill limits liability protection that applies to a provider of an interactive computer service (e.g., a social media company) for claims related to content provided by third parties if a provider promotes health misinformation during a declared public health emergency. Specifically, the liability protection (sometimes referred to as Section 230 protection) shall not apply to a provider that promotes health misinformation using an algorithm unless the algorithm uses a neutral mechanism for the promotion, such as chronological functionality. The Department of Health and Human Services must, within 30 days, issue guidance about what constitutes health misinformation.