“We did a study on why parents didn’t have their children complete the series and the most common reason was they weren’t reminded,”said Dr. Rebecca Perkins, an obstetrics and gynecology professor at Boston University. “They’d say, ‘Wait, I thought they were done.’ They just didn’t realize.”

Simple strategies like booking follow-up appointments at the time of the first dose, or sending reminders via text, phone or email, have been found to be effective in increasing the likelihood that patients complete the HPV vaccine course, and may be useful tools for making sure patients get both doses of the COVID-19 vaccine.

A review of this research in 2019 found that combining approaches (such as having doctors remind patients about the second dose when they visit, as well as providing text message reminders and setting up appointments) was most effective at increasing completion rates for the HPV vaccine. The CDC has required every state put together a COVID-19 vaccine distribution plan that includes strategies for ensuring patients come back for their second dose. Those strategies vary by state, but typically include some of the strategies that have proven effective for the HPV vaccine. States also already have vaccine database systems (with the exception of New Hampshire, though it’s building one now) that should make this easy to roll out, according to Dr. Marcus Plescia, the chief medical officer for the Association of State and Territorial Health Officials.