Microsoft (NSDQ: MSFT) and Google (NSDQ: GOOG) have been steadily adding partners to their competing health platforms, and both companies made new announcements today. Google said it had teamed up with CVS so that millions of CVS customers would be able to easily transfer their prescription history to an online Google Health account; Microsoft said it would integrate its HealthVault platform with Amalga, a Microsoft technology that some hospitals use to aggregate patient data. New York-Presbyterian Hospital signed up for Amalga and HealthVault today.

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The companies are building platforms that anybody can use to store medical records online. It’s unclear, though, how either platform is doing since neither company has said how many people have actually signed up for accounts. The recent economic stimulus bill, which allocates billions to the goal of electronic health records for every American, should help both systems. In a recent interview, David Cerino, the general manager of Microsoft’s consumer-health solutions group, told me that electronic records themselves would not prove to be too useful, without the use of platforms like HealthVault, which lets patients share those records with others and interact with them.

Update: Worth mentioning that Microsoft already had a relationship with CVS similar to the one that Google announced today. Microsoft announced that HealthVault partnership last June.