Table 1.

The codebook used for qualitative descriptive analyses of 47 Yorktown, Virginia, Fleet Antiterrorism Security Team Marines’ 235 written reasons for why, in February 2021, they planned to decline the COVID-19 vaccine.

Label	Definition	Description of how to know when code occurs	Keywords or phrases	Positive example (is this code)	Negative example (is not this code)
Difficulty understanding health information [53,54]	Marines do not understand or misunderstand basic medical information.	Responses that inadequately represent (most likely due to honest lack of understanding) what is currently known about the vaccine’s ingredients, effectiveness, side effects, outcomes, etc.	FDAa; CDCb; mRNAc; effective; effectiveness; study; studies; too soon; early to know; immunity; side effects; takes years; not approved; not proven	“I’ve heard that [the vaccine] makes you very susceptible to sickness and weakens your immune system.” “MRNA vaccines have never been used before”	“It is my right to refuse it” “It uses fetus and fetus cell lines of aborted babies”
Perceived low susceptibility of COVID-19 and its severity [55]	Marines underestimate their risk of contracting COVID-19 and of a serious negative outcome.	Responses that suggest a low expected likelihood of contracting COVID-19 and of falling seriously ill.	No symptoms; young; healthy; likelihood; slim; survival rate; no danger	“I don’t have COVID and have never had a single symptom of it, so therefore I don’t need it.” “Flu hasn’t affected me any different”	“Can cause you to be sterile” “I don’t like needles”
Concern over vaccine safety and potential side effects [56]	Marines expect the vaccine or side effects will cause physical pain or discomfort.	Responses mentioning known and unpleasant side effects.	Needles; side effects; symptoms; allergic reaction; getting sick	“I don’t like needles” “Possibly getting sick and being unable to train in DM course”	“Not FDA approved/licensed” “I don’t want it”
Status quo bias may impact preventive pandemic behaviors [56,57]	Marines postpone getting the vaccine if doing so does not have an immediate benefit for them.	Responses mentioning drawbacks to getting vaccinated and no benefits.	No benefit; not a requirement; voluntary; wear mask; socially distance	“Not a requirement for the Marine Corps or deployment.” “There isn’t any benefit to getting the vaccine such as being immune to COVID-19 and not having to wear a mask or maintain 6 feet of social distance”	“I’ve already received a flu shot” “I have other things to worry about”
Distrust in health care [58]	Marines distrust the health care system in general or have had bad experiences in health care settings.	Responses mentioning trust in the health care system, in the CDC, and in the vaccine.	Trust; Pfizer; questionable history; rushed; wrong about the virus	“I don’t trust it at all” “I rarely trust anything that is newly developed with no history of defects or flaws.”	“I’d rather wait and see how people’s body respond to it” “Standard set low, CDC said it only needed to be 50% effective”
Social norms may influence attitudes and beliefs about vaccines [55,59]	Marines have no role models—family members, community members, etc—who are seen endorsing the behavior.	Responses indicating that trusted friends, family, and health care providers are not getting vaccinated.	Family; peers; Marines; doctor; friends	“Other marines I trust aren’t getting it” “I asked my doctor from home & he said wait a couple years”	“Side effects are negative” “Short term effects show facial paralysis in several cases”
Believing in COVID-19 conspiracies [60]	Marines have strong, irrational, and disproven beliefs against the vaccine.	Responses that indicate believing in nonvalidated, mis- or disinformation about the COVID-19 vaccine.	Test dummy; guinea pig; political gain; election time; media; democrats	“Don’t want to be a test dummy for the military.” “Can cause you to be sterile.”	“The vaccine is not guaranteed to work” “Flu has been around for 500 years and finally got vaccinated in 1930 by injecting a weaker virus into you”
Other or unclear	Combination of categories with fewer than 1% of responses each.	Responses with prosocial beliefs, religious concerns, or vague.	Does not fit in any other category.	“It goes against my religious beliefs” “Personal beliefs”	“99.98% survival rate for my age group” “I simply don’t want the vaccine... Or is it mandatory?”

^aFDA: US Food and Drug Administration.

^bCDC: Centers for Disease Control and Prevention.

^cmRNA: messenger RNA.