I plan to travel to US and I have two completed doses of the Sputnik vaccine. However, Sputnik is not an approved vaccine for travel to US. Do I still need to receive a full course of the approved vaccine e.g. two complete doses of Pfizer vaccine on top of my already-completed two doses of Sputnik?
My understanding is that you currently would require proof of a full course (one or two shots, as required) of one of the USDA or WHO approved vaccines.
However these requirements are being relaxed worldwide and it's possible that in matter of weeks or months that will no longer be required. For example, come October 1, 2022 (two days from now) it will no longer be a requirement for entry to Canada. It's also possible that nothing will change for the US, of course. Anecdotally, the US is more of a attestation than the detailed document check verification you might expect from the web page (but I would not suggest lying, of course, just be prepared that if you do go to the trouble, expense and risk of getting additional shots they may not look too closely).