Read on Twitter
1-One barrier I foresee for the #covid19 #vaccine is attrition between the 1st and 2nd doses. I was curious how this has gone for HPV vaccines, which require either 2 or 3 shots spaced months apart. How many ppl drop off between doses & why? 
2-Anytime you need ppl to do things more than once, youâll have dropoff. Logistical & access issues are often why. 1 study found that clinics not reminding & relying on parents to schedule it on their own were why teen girls didnât complete HPV vax. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4964719/#!po=0.757576
3-Back in 2010, 44% of teen girls got the 1st HPV shot, but only 27% got all 3. https://www.npr.org/sections/health-shots/2010/11/08/131170901/hpv. In 2020, 71.5% of teens got the 1st shot, but just 54.2% were fully up to date. https://www.cdc.gov/mmwr/volumes/69/wr/mm6933a1.htm#F1_down
4-Lack of access to care, suboptimal insurance, living in a rural area, parental attitudes & fears, forgetting, unawareness that a 2nd dose is required, & low perceived risk for HPV are some barriers. https://jamanetwork.com/journals/jamapediatrics/article-abstract/1779687 & https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2757996
5-A pop-based Australian analysis in 2011 found that 85% of teen girls who started the HPV schedule completed it. I donât know why this is higher in Aus than US. https://link.springer.com/article/10.1186/1741-7015-11-227
6-This isnât my subject matter area, but based on the articles I read, it seems key that clinics (or wherever ppl get the Covid vax) actively schedule the next appt, actively send them reminders to return, & stress that they are not vax until they complete the schedule.
7-I also think itâs important to note that ppl are less likely to get a vax if they donât think theyâre at risk. We know a lot of ppl donât think they or their kids are at risk for Covid. How can we design messages to persuade them?
Added later: the shingles vax also needs 2 shots: about 80% get both shots. Although we donât know for sure, incomplete vax schedules could -> viral resistance & mutations. Another solution I didnât know is 
incentives to doctors for 2nd shot. Source: https://www.cbsnews.com/news/covid-vaccine-two-shots-undermine-efforts/
incentives to doctors for 2nd shot. Source: https://www.cbsnews.com/news/covid-vaccine-two-shots-undermine-efforts/
