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Effective June 30, 2018, if you have not upgraded to a current browser you will no longer be able to view or make transactions on MerckVaccines.com. To protect your credit card information, Merck follows security requirements mandated by the PCI Security Standards Council. The PCI Security Standards Council has mandated that all companies that transact payments with credit cards must restrict the use of insecure browsers.

You can learn more about the specific PCI requirement here.