Lotteries are an effective strategy for increasing COVID-19 vaccine uptake: experimental evidence from Pakistan

ISRCTN	ISRCTN18352233
DOI	https://doi.org/10.1186/ISRCTN18352233
Sponsor	Institute of Development and Economic Alternatives (IDEAS)
Funder	International Growth Centre

Submission date: 20/07/2026
Registration date: 26/07/2026
Last edited: 22/07/2026

Recruitment status: No longer recruiting
Overall study status: Completed
Condition category: Infections and Infestations

Prospectively registered

Protocol

Statistical analysis plan

Results

Individual participant data

Record updated in last year

Plain English summary of protocol

Not provided at time of registration

Contact information

Dr Hina Khalid
Principal investigator, Scientific, Public

HBKU Minaretein Building, 3rd Floor
Doha
-
Qatar

ORCID ID	0000-0002-3673-7237
Phone	+974 51225942
Email	hkhalid@hbku.edu.qa

Study information

Primary study design	Interventional
Allocation	Randomized controlled trial
Masking	Open (masking not used)
Control	Placebo
Assignment	Parallel
Purpose	Prevention
Scientific title	Lotteries are an effective strategy for increasing COVID-19 vaccine uptake: experimental evidence from Pakistan
Study objectives	To examine the effect of behaviorally informed messages (vaccine mandates, side-effects minimization, vaccine manufacturer choices) and financial incentives (cash-prize lottery) on behavioral commitment to register for and receive COVID-19 booster or primary vaccination.
Ethics approval(s)	Approved 20/10/2022, Research and Development Solutions (RADS) (Suite # 3, 2nd Floor, Ali Akbar House, G-8 Markaz, Islamabad, Lahore, 54600, Pakistan; +92 51 8436877; info@resdev.org), ref: no reference provided
Health condition(s) or problem(s) studied	COVID-19 vaccine hesitancy and vaccination/booster uptake
Intervention	A five-arm randomized controlled trial where participants were assigned to a control group or one of four behavioral treatment arms: (1) vaccine mandates emphasizing travel and work requirements, (2) side-effects minimization focusing on safety, (3) vaccine manufacturer options (Pfizer or Moderna), and (4) a cash-prize lottery entry for PKR 30,000. Randomization procedure: Enumerators collected data through a digital data collection platform, SurveyCTO. Randomization was carried out at the individual level via SurveyCTO. SurveyCTO generated a randomized sequence for placing respondents into treatment and control arms and that was utilized. Participants were asked a series of questions to understand vaccine preferences, and their demographic and behavioral characteristics. During the course of the questions, they were exposed to one of the 4 treatments (or not if they were in the control group). At the end of the survey participants were offered “opt in” booster shots; enumerators asked the participants if they were willing to sign up for the booster shot (or primary vaccination for those who were not previously vaccinated) during their visit to the hospital that day. Participants could then walk over to the vaccination site within the same hospital. So, exposure to the treatment message was one time i.e. only at the time of the survey. Follow-up survey: A short follow-up survey with a subset of 744 randomly selected participants was conducted via telephone on February 14, 2023. Due to budget constraints, we were only able to contact a random subset of respondents. There were two outcome variables which measured the ‘uptake’ of the COVID-19 booster shot: (i) immediate vaccination i.e., if the participant got vaccinated on the same day, and (ii) subsequent vaccination i.e., if the participant got vaccinated a few days later.
Intervention type	Behavioural
Primary outcome measure(s)	Behavioral commitment to register for getting boosted measured using a binary variable indicating whether the respondent consented to sign up for same-day vaccination during their hospital visit at Immediate / On-the-spot (measured immediately following exposure to the treatment messages during the hospital visit)
Key secondary outcome measure(s)	Immediate vaccination measured using if the participant got vaccinated on the same day (yes/no) via a phone survey at follow-up Subsequent vaccination measured using if the participant got vaccinated a few days later (yes/no) via a phone survey at follow-up
Completion date	14/02/2023

Eligibility

Participant type(s)
Age group	Mixed
Lower age limit	18 Years
Upper age limit	90 Years
Sex	All
Target sample size at registration	1564
Total final enrolment	1564
Key inclusion criteria	1. Individuals visiting a large, urban hospital for routine care 2. Have not previously received one or both doses of the booster shot, or have not previously been vaccinated against COVID-19
Key exclusion criteria	Participants who did not meet the routine care or booster-unvaccinated criteria
Date of first enrolment	21/12/2022
Date of final enrolment	14/02/2023

Locations

Countries of recruitment

Pakistan

Study participating centres

Results and Publications

Individual participant data (IPD) Intention to share	Yes
IPD sharing plan	The datasets generated during and/or analysed during the current study will be available upon request from Dr. Hina Khalid hkhalid@hbku.edu.qa

Study outputs

Output type	Details	Date created	Date added	Peer reviewed?	Patient-facing?
Other files	Blog post		20/07/2026	No	No
Other publications	Policy brief		20/07/2026	Yes	No

Additional files

49946 blog post.pdf: Blog post
49946 Khalid et al policy brief July 2023.pdf: Policy brief

Editorial Notes

20/07/2026: Trial's existence confirmed by Research and Development Solutions (RADS).