Table 1.

Numbers and percentages of tweets related to each COVID-19 vaccine topic (N=1,499,421).

Theme and topics		Top terms contributing to the topic model	Total tweets, n (%)	Example paraphrased tweeta (date posted)
Theme 1: Opinions and emotions around vaccines and vaccination
	Opinions about vaccination	people, get, take, go, want, make, like, think	227,840 (15.20)	“It is pathetic to see the low trust in science and the government. People need to see leaders and politicians on TV to receive the vaccine to convince them that the vaccine is safe.” (December 18, 2020)
	Positive emotion around vaccination	get, good, first, day, today, work, one, feel	89,117 (5.94)	“After getting the first dose of the covid-19 vaccine today, I can finally breath some fresh air and feel there is hope in life.” (January 23, 2021)
	American president	Trump, Biden, American, president, gate, bill, plan, administration	88,440 (5.90)	“There are more lies than usual in today’s press. Biden is being portraited as anti-vaccine. This is not correct. In fact, he said on Wednesday he trusted the vaccines and the scientists, while accusing President Trump of playing politics with a potential covid-19 vaccine.” (September 16, 2020)
Theme 2: Knowledge about vaccines
	Educating communities	question, read, answer, expert, article, community, immunity, black	96,532 (6.44)	“You can learn more about the covid-19 vaccines in our upcoming town hall meeting. We will address any questions and concerns on January 13, 2021, 2-3:30 PM (EST).” (January 7, 2021)
	Measures to control community spread	mask, get, need, go, still, available, end, life	89,008 (5.94)	“Even though covid-19 vaccines are an important step in slowing down the spread of the virus, people still need to continue taking all precautions: wear a mask, maintain physical distance from others, and keep your hands clean.” (January 19, 2021)
	Immunity and mutation	flu, year, new, may, variant, work, effective, strain	88,327 (5.89)	“They say that coronavirus resembles the flu virus. As we know, the flu virus mutates. Therefore, they need to create different flu shot every year into order to fight off the virus, but there hasn’t been a flu vaccine that is 100% effective. So good luck with making the covid-19 vaccine.” (May 11, 2020)
	Functioning of vaccines	people, effect, test, risk, side, side effect, immune, death	81,438 (5.43)	“Both vaccines use mRNA technology which contains instructions that tell our cells how to make a protein that triggers an immune response inside our bodies.” (December 21, 2020)
Theme 3: Vaccines as a global issue
	Global cooperation and support	world, country, global, pandemic, access, need, develop, effort	108,366 (7.23)	“On Thursday, WHO [the World Health Organization] warns against ‘vaccine nationalism.’ No one country is safe if poor countries can’t get access to the vaccines.” (August, 9, 2020)
	Vaccine progress around the world	UK, China, EU, Russia, first, country, approve, news	83,156 (5.55)	“On Tuesday, German health minister Jens Spahn joined EU [the European Union] to place restriction on exporting covid-19 vaccines. This came amid discontent over the delay in rolling out the AstraZeneca vaccine to member countries.” (January 26, 2021)
	Economic impact	new, case, death, news, rollout, rate, high, report	61,360 (4.09)	“A rise in new covid-19 cases outweigh positive vaccine news. Shutdown fears sink global markets. US coronavirus deaths are above 250,000.” (November 9, 2020)
	Vaccination drive in India	India, drive, minister, Indian, speed, warp, health, warp speed	58,369 (3.89)	“India clears covid-19 vaccine makers Serum Institute of India (SII) and Bharat Biotech to start the world’s largest immunization drive.” (January 3, 2021)
Theme 4: Vaccine administration
	Instruction on getting vaccines	county, health, state, appointment, update, plan, site, distribution	106,544 (7.11)	“Health departments will each announce their vaccine availability and locations. Eligible individuals at the federally qualified health center will be contacted regarding access to a covid-19 vaccine.” (December 30, 2020)
	Vaccine rollout	worker, care, health, first, receive, healthcare, hospital, staff	85,623 (5.71)	“We have many sites delivering the covid-19 vaccines to the top priority group. Please be patient and if you are in the top priority group, you will be contacted.” (January 17, 2021)
	Progress on vaccine administration	dose, million, first, receive, week, Pfizer, people, first dose	74,577 (4.97)	“Since Tuesday’s update, Louisiana has administered 25,133 additional covid-19 vaccines. The second doses started being administered this week. 7,068 people have been fully vaccinated. In total, since mid-December, 81,585 doses have been administered.” (January 7, 2021)
Theme 5: Progress on vaccine development and authorization
	Clinical trials	trial, clinical, Pfizer, Moderna, phase, effective, clinical trial, oxford	99,754 (6.65)	“There are 70 covid-vaccines under development. Moderna is one of the first to test their covid-19 vaccine on humans. If the trial is successful, Moderna could reach the final stage of testing by Fall 2020.“ (April 26, 2020)
	Use authorization	use, FDA, approve, emergency, approval, Pfizer, emergencyuse, health	60,970 (4.07)	“The FDA’s [US Food and Drug Administration’s] vaccine advisory committee has unanimously approved an emergency use of the covid-19 vaccine made by Pfizer and by Moderna.” (January 19, 2021)

^aThe tweets are paraphrased to protect users’ privacy.