Tourists from India travelling abroad have reported having trouble with the QR code printed on their COVID-19 vaccination certificates. Many have said that they were detained by authorities outside India or were not allowed to board flights because, when the QR codes were scanned, messages like "your certificate has been revoked" popped up. Some tourists have also reported being denied visas because the QR codes were not being read by the scanner. Experts say that, to avoid any such problems, travelers should print out their new vaccine certificates every 15 days and should check if the QR codes are functional before embarking on a journey abroad.