In early 2022, various kinds of text messages were sent to over 100,000 residents of Brabant-Zuidoost who had not yet received a booster jab from the GGD. The results show that the most effective variant − in the 6 days after receiving the text message − led to a 3.2% increase in the number of vaccinations administered. This was the text message saying 'Jouw boosterprik ligt voor je klaar' (You can now book your booster vaccination) plus a randomly allocated date, time and location.

Why this experiment was conducted: more bookings needed for booster vaccinations
The repeat dose restores protection against the COVID-19 virus. This booster vaccination provides 97% protection against hospitalisation due to the virus. To increase the number of bookings for booster vaccinations in early 2022, the GGD conducted a pilot study using text messaging reminders.

Type of intervention: Six different text messages
Six different text messages were sent.
• The text messages of 25 January 2022 used ownership ('Jouw boosterprik ligt voor je klaar') or efectiveness ('Een boosterprik beschermt voor 97% tegen ziekenhuisopname' (A booster vaccination provides 97% protection against hospitalisation)). The third text message contained basic information.
• In the text messages of 1 February 2022, ownership was repeatedly emphasised. Information was also added about the opening hours of the GGD site, or even giving a specific time when the vaccine could be administered (e.g. 'Je bent op 05-02-2022 tussen 16:00 en 17:00 uur welkom op Haverdijk 11 in Helmond' (You are welcome between 16.00 and 17.00 on 5 February 2022 at Haverdijk 11 in Helmond).

Method used: RCT
In an experiment, text messages were randomly sent on 25 January and 1 February to 30,000 and 75,000 residents of Brabant-Zuidoost, respectively, who had not yet received a booster vaccination from the GGD. On 25 January, this involved three groups each consisting of 10,000 residents. In addition, there was a control group of 10,000 residents who did not receive text messages. On 1 February, there were three groups each consisting of 25,000 residents, and once again a control group consisting of 25,000 residents. For all eight groups, vaccination take-up was measured six days after the text messages were sent.

Result obtained: behavioural techniques led to more COVID boosters
Residents who received a text message using ownership framing were significantly more likely to receive a booster vaccination (4.5%, a significant increase of 1.2%). The text message stressing the effectiveness of the booster vaccination also led to significantly more COVID boosters being administered (+1%). In the control group, 3.3% received a COVID booster six days after the text messages sent on 25 January. In the group that received the basic text message, 3.6% did so, meaning there was no significant difference between these two groups. Of all the text messages, the most effective one was the variant of 1 February giving a specific date, time and location, combined with ownership framing. This text message resulted in 3.2% more booster vaccinations being administered in the six days after the message was received (6.3% versus 3.1% for the control group not receiving a text message). Text messages using ownership framing and containing information about opening hours also led to significantly more (+1.0 to +1.2%) booster vaccinations being administered. The overall impact of this text messaging campaign was a rise of roughly 1.6 percentage points in the vaccination rate.

Impact: contribution to public health in the Netherlands
A text message campaign is a relatively cheap and easy intervention that can significantly increase the number of booster vaccinations. It was also found that the wording of the text message can make a difference. There are also drawbacks to a large-scale text message campaign. Seven complaints were received from residents saying that the message was not appreciated by them, for example. In addition, roughly twenty responses were received from people reporting that the addressee had since died.

It was estimated that nationwide there were about 3 million people who met the same criteria as this group. If all of them were to be sent the most successful text message variant by the GGD, it is estimated there would be a surge in the number of vaccinated residents by 96,000 over the six days following its receipt.

Source:https://www.binnl.nl/home+-+en/knowledge/publications/bin+nl+publications/HandlerDownloadFiles.ashx?idnv=2719979