Dear Laura,
Thank you for contacting us.
Please check with your airline's agent if you have to go out of the Vietnam Immigration gate (isolated area) to reach the baggage claim belt for transit flight via Vietnam. If yes, you need to have a visa to pass Immigration checking booth. In this case you would need to apply for a visa.
We hope that the information above is helpful for you. Let us know if you have any further concerns.
Best regards,
Grace, Nguyen (Ms.)