Content of each experimental treatment message used along with the corresponding nudge technique employed
| No | Nudge technique | Content | Message code |
| 1 | Descriptive norm | Around 70% of Malaysians said that they will get the COVID-19 vaccine. Will you join them? Source: Ministry of Health, Malaysia; 31 December 202012 | DN(70%) |
| 2 | Descriptive norm | The COVID-19 vaccine was tested with thousands of people, including the elderly, and people with existing health conditions. Now, millions of people worldwide have received it. When it’s your turn, you can be confident that it is safe and effective. Source: Kyriakidis et al. NPJ Vaccines. 2021 February 22;6(1):2892 John Hopkins Coronavirus Resource Center, USA93 | DN |
| 3 | Influence from a government official and health authority, and descriptive norm | Malaysia’s Health Director General, Dr Noor Hisham Abdullah, and 9 out of 10 healthcare workers in Malaysia have received the COVID-19 vaccine. They recommend that you get it too. Source: COVID-19 Immunisation Task Force, Malaysia; 23 February, 29 March 202194 95 | HCW |
| 4 | Negative attribute framing | Only 4 out of 100 people who received the COVID-19 vaccine experienced side effects. Source: Ministry of Health, Malaysia; 2 April 202196 | NF |
| 5 | Positive attribute framing | 96 out of 100 people who received the COVID-19 vaccine did not experience any side effects. Source: Ministry of Health, Malaysia; 2 April 202196 | PF |
| 6 | Risky choice framing (safety) | There are 0 deaths caused by the COVID-19 vaccines. On the other hand, over 1400 people have died due to COVID-19 infections. Source: Ministry of Health, Malaysia; 18 March 202197 Crisis Preparedness and Response Centre (CPRC), Malaysia; 23 April 202198 | RC(S) |
| 7 | Risky choice framing (side effects) | Only 4 in 1 million people who received the COVID-19 vaccine experienced blood clots. On the other hand, 200 000 in 1 million people infected with COVID-19 experienced blood clots. Source: Torjesen. The British Medical Journal. 2021;373:n100599 Malas et al. EClinicalMedicine. 2020 December; 29:100639.100 | RC(SE) |
| 8 | Control message | Get the COVID-19 vaccine. It’s safe and effective! | N/A |
Each message is assigned a code to ease referencing.