Vaccine Targeting Rogue and Opaque Letters Act of 2021 or the Vaccine TROL Act of 2021 This bill prohibits sending bad faith patent demand letters concerning a product relating to COVID-19 during the declared public health emergency. A patent demand letter is a written communication claiming that the recipient may be liable for patent infringement. Bad faith means making knowingly false or misleading statements, making claims with reckless indifference for the truth, or omitting information with the intent to deceive. Bad faith representations shall include false or misleading claims about the sender's right to assert a patent and whether lawsuits have been filed. They also include making written demands for compensation for invalid patents or to demand compensation without identifying the ultimate parent entity of the letter sender. Under this bill, a patent demand letter related to COVID-19 is presumed to have been sent in bad faith if the sender fails to respond within 10 business days of receiving a request by the letter recipient for (1) certain information required by this bill, or (2) the patent claim that the sender reasonably believes is being infringed. The sender shall have an affirmative defense that it acted in good faith by proving that its misstatements or omissions were unintentional and that it made an error in spite of procedures to avoid such errors. The Federal Trade Commission and state attorneys general may bring actions to enforce these provisions.