The studies were too heterogeneous for a meta-analysis, so we present a narrative synthesis of the results.
Study characteristics
We found seven studies that fulfilled our inclusion criteria [
9,
16‐
21]. A summary of the study characteristics is in Table
1 and a detailed table of study characteristics is in Additional file
3. One of the papers, Tidwell 2019, reported two interventions, one of which was an excluded intervention—a TV advertisement—and is listed along with the excluded studies in Additional file
2. All were randomized controlled trials (RCTs), apart from Hu 2018, which was a non-randomised but controlled trial [
17]. One study reported only health outcomes [
18], four reported only behavioural outcomes [
16,
19‐
21], and two reported both health and behavioural outcomes [
9,
17].
Table 1
Summary study characteristicsa
| US | RCT | Flu | Workplace | 144 Healthy adults | Personally controlled health record program | Messages on influenza illness and prevention, tailored based on survey information provided and on postcode | Four monthly bulletins providing information on cardiovascular disease, stroke, skin cancer and sun protection, and guidelines for a healthy diet | 16 weeks | ● The rate of work attendance despite a respiratory illness, ● Question in exit survey on hand hygiene ● Question in exit survey on cough etiquette |
| China | Non-randomised but controlled trial | HFMD | Kindergartens and home | 10 staff, 60 parents and 60 healthy children | WeChat | WeChat education group (for GPs, staff, and parents) + Usual care | Usual care: health education, delivered face to face. | 3 months | ● Incidence of HFMD ● Proportion of children who mastered the correct way of washing hands (measured at end of treatment) ● Proportion of children who formed good habits of washing hands (measured at end of treatment) |
| China | RCT | HFMD | Community Health Service Center and home | Parents of 120 children with HFMD | WeChat | WeChat education group (for GPs and parents) | Usual care: health education, delivered face to face. | 14 days | ● Duration of rash ● Time to recovery |
| England | RCT | n/a | Service station bathrooms | Highway service station bathroom users, more than 198,000 restroom uses over 32 days | Text-only message, displayed on an electronic dot matrix screen over the entryway to the 2 restrooms | 14 different intervention messages covering seven domains, max 48 characters, all included the word ‘soap’. | Blank control: no message on the board Positive control: “Wash your hands with soap.” | July–September 2008 | ● Soap use ratio ● Soap dispenser use divided by number of people in the bathroom during the intervention period (1-h intervals) |
| UK | RCT | RTIs | Online | 20,066 adult patients from 344 practices, who had at least one other individual living in the household | Web-based and email prompts | Four weekly web-based sessions, that provided information, developed a plan for handwashing, reinforced helpful attitudes and norms, addressed negative beliefs and used tailored feedback. Automated emails were used to prompt participants to use sessions and complete questionnaires | No treatment: The control group did not have access to the intervention webpages, but they had monthly emails to prompt them to complete the questionnaires. | 4 months | ● Self-reported infections in user (incidence and severity of respiratory infections, incidence of gastrointestinal infections) ● Self-reported incidence of respiratory infections in household members ● Self-reported handwashing ● Health care use as assessed from medical records (number of GP consultations and antibiotic prescriptions) |
Study 2 | India | RCT | n/a | Home | 617 new mothers, 605 mothers of 4–7 year olds | Mobile phone audio messages (all); reminder texts (new mothers only) | Audio phone messages of 90s, twice weekly, conveying health messages via a fictional dialogue between a doctor and a mother; Text reminders to practice the target behaviours | No intervention (though control sample also had to own a phone) | 8 weeks (new mothers), 4 weeks (mothers of 4–7 year-olds) | ● Handwashing with soap at key occasions; ● Measured 21 days after the end of the intervention using sticker diaries |
| China | RCT | HFMD | Home | 3000 parents of vaccinated healthy children aged 0–3 | Text messages | Messages of < 50 words, about knowledge, prevention and treatment of HFMD, sent at least weekly, with a total of 16–20 messages. | No intervention | 5 months | ● Proportion of children who wash hands before eating and after going to the toilet (measured at baseline and 1 year) ● Proportion of children who wash hands after going out (measured at baseline and 1 year) |
Two of the studies were conducted in the UK [
9,
19], one in the US [
16], three studies in China [
17,
18,
21], and one in a relatively low income part of India [
20]. All three Chinese studies concerned hand foot and mouth disease (HFMD) [
17,
18,
21], one UK study focussed primarily on respiratory tract infections (RTIs, Little [
9]), and the one US study was on influenza [
16]. Two studies aimed to increase the incidence of hand washing with soap, without being focussed on the prevention of a particular disease [
19,
20].
Regarding the setting and population, three studies targeted parents of young children [
18,
20,
21], one targeted parents and staff in kindergartens [
17], one was set in the workplace [
16], one in service station restrooms [
19], and one targeted the general adult population [
9]. The participants in the four studies that targeted parents of young children had a lower average age than participants in the two trials with a workplace or general population setting, see Additional file
3. The sample sizes varied from hundreds [
16‐
18] to thousands [
20,
21] to tens of thousands [
9] to hundreds of thousands [
19]. One of the smaller trials, Bourgeois 2008, had a smaller sample than hoped for because it was set in the workplace and there was corporate restructuring during the recruitment period [
16].
Two studies, Hu 2018 and Hu 2019, delivered their interventions via WeChat, a Chinese platform that is similar to Whatsapp, allowing users to send free messages to phone contacts that also use WeChat; to transfer pictures, videos, or speech; and enabling group chat [
17,
18]. In both studies, a WeChat group was set up for health care workers and participants. Health care workers could upload health educational materials and participants could ask them questions about HFMD. Both WeChat interventions operated in the same manner, but they had different targets and therefore contents: one was for healthy children and included material that promoted knowledge of prevention methods [
17], while one was for the parents of HFMD patients with a target of promoting knowledge of clinical treatment including nursing [
18].
Germ Defence, Little 2015, is a web-based intervention plus email [
9]. Participants were recruited from GP practices and offered a web-based session each week for 4 weeks, which provided information about the importance of influenza and the role of handwashing, encouraged users to develop a plan to maximise goal and intention formation for handwashing, reinforced helpful attitudes and norms, and addressed negative beliefs using tailored feedback. Automated emails were used to prompt participants (to complete the monthly questionnaires, and—in the intervention group—to use the sessions).
Tidwell 2019 sent weekly 90 s audio messages about hand hygiene to participants’ phones, supplemented with text message reminders to some participants [
20]. The messages were branded as a part of a campaign and took the form of a fictional dialogue between a local doctor and a mother. Mothers of children from 4 to 7 years received messages for 4 weeks, whereas new mothers received messages for 8 weeks. Messages to the former were about hygiene topics, while messages to the latter included more general maternal health messages as well. New mothers also received reminder texts to practice the target behaviours.
Wu 2020 sent text messages of less than 50 words about knowledge, prevention and treatment of HFMD [
21]. The messages were sent at least once a week starting 1 month before the peak time for hand foot and mouth, with a total of 16 to 20 messages over 5 months.
Bourgeois 2008 sent messages via a personally controlled health record program [
16]. Enrolled subjects completed online health risk assessment surveys, the responses to which drove a decision support system to generate and send tailored health messages for participants in the intervention group. These messages were sent to participants’ personally controlled health record inbox, and participants were simultaneously notified with a standard, plain-text email instructing them to visit and log on to their personally controlled health record to review the message. The intervention group received messages on influenza illness and prevention, tailored based on information provided in baseline and seven bi-weekly surveys, and on postcode. There were five types of health message: vaccine reminders, respiratory illness advice, influenza alerts, weekly influenza risk maps, and monthly educational bulletins. For instance, in the health message about what to do if a household member has respiratory illness, participants were advised to avoid close contact, stay home when sick, cover your mouth and nose, wash your hands, and avoid touching your eyes, nose or mouth.
Judah 2009 used electronic billboards at the entrance to service station restrooms [
19]. Messages were a maximum of 48 characters, were in capital letters, and flashed for the duration of their presentation to attract attention. The researchers tested two messages from each of seven domains; all included the word ‘soap’. The domains were:
-
Knowledge of risk: Inform people about a fact they may not know;
-
Knowledge activation: Remind people of what they know already or convince them of the importance of what they know;
-
Norms or affiliation: Raise concern for social judgments on people’s hygiene behaviours because of the knowledge that others might be concerned with standards for acceptable behaviour;
-
Status or identity: Help people to feel that hand washing—or more broadly, cleanliness and being hygienic—is an important aspect of their self-image;
-
Comfort. Emphasize positive sensory qualities of having clean hands;
-
Disgust: Trigger the arousal of a “yuck” response;
-
Cue. Provide people with a behavioural rule triggered by an object in the environment or an event.
The study using the personally controlled health record program (Bourgeois 2008) had an active control condition [
16]. Control participants were sent monthly bulletins (four in total) providing information on cardiovascular disease, stroke, skin cancer and sun protection, and guidelines for a healthy diet. The service station restroom trial had both a passive control (blank board) and an active control (“Wash your hands with soap”). The other trials all had a no intervention/ usual-care control.
In three studies, Judah 2009, Tidwell 2019 and Wu 2020, participants were passive receivers of the intervention [
19‐
21]. In two studies, Little 2015 and Bourgeois 2008, they completed questionnaires [
9,
16] and in two studies, Hu 2018 and Hu 2019, the participants could interact with each other and with health care professionals [
17,
18].
All seven studies either sent participants educational material or, in the case of [
19], had conditions that targeted knowledge. Both of the studies that asked participants to complete questionnaires (Little 2015 and Bourgeois 2008) also used them to provide tailored feedback [
9,
16]. One of these two studies, Little 2015, also used planning to support the formation of intentions to wash hands, monitored handwashing behaviour, reinforced helpful attitudes and norms, and addressed negative beliefs [
9]. Three studies sent prompts as well as the main intervention: Bourgeois 2008 sent emails to remind the participants to log-on to their personal health care record [
16], Little 2015 emailed to remind them to complete questionnaires and use the intervention sessions [
9], and Tidwell 2019 sent texts to one group of participants to remind them to practice the target behaviours [
20].
The restroom trial messages in Judah 2009 were developed at a workshop of experts, based on empirical data and theoretical domains from behaviour change theory [
19]. Tidwell 2019 piloted messages on a group that was similar to the target participants, to check for comprehensibility and acceptability of content [
20]. Little 2015 developed the Germ Defence intervention iteratively with users, with the “person-based approach” [
9].
Health outcomes
Three trials reported health outcomes: [
9,
17,
18] (see Table
3). Little 2015 was conducted in the UK, focussed on RTIs, and was judged to be at low risk of bias; Hu 2018 and Hu 2019 were conducted in China on HFMD; Hu 2018 was judged to be at high risk of bias and Hu 2019 was judged have some concerns. All reported that they were successful at reducing either incidence or duration of illness, and Little 2015 was also successful at reducing the use of healthcare resources (consultations and antibiotics).
Table 3
Summary of health outcomes
| Incidence of HFMD | 13.3% (4/30) | 0% (0/30) | n/a |
| Duration of rash in days, M (SD) | 7.43 (1.9) | 3.65 (0.8) | p < 0.05 |
Time to recovery in days, M (SD) | 13.04 (2.6) | 6.66 (1.5) | p < 0.05 |
| Number reporting one or more episodes of RTI at 16 weeks | 59% (5135/ 8667) | 51% (4242/ 8241) | Multivariate risk ratio 0·86; 95% CI 0·83–0·89; p < 0·0001 |
Number reporting one or more episodes of gastrointestinal infections at 16 weeks | 25% (1821/ 7292) | 21% (1376/ 6410) | Multivariate risk ratio 0.82; 95% CI 0.76–0.88; p < 0.0001 |
Number of respiratory infections at 4 months, M (SD) | 1.09 (1.36) | 0.84 (1.13) | Multivariate incident rate ratio 0.75; 95% CI 0.72–0.79; p < 0.0001 |
Number of days of moderate or bad symptoms, M (SD) | 2.60 (4.44) | 2.08 (4.00) | Multivariate incident rate ratio 0.92; 95% CI 0.87–0.98; p < 0.0001 |
Antibiotic use in primary care within 4 months | 6% (617/9579) | 6% (535/9540) | Multivariate risk ratio 0.83; 95% CI 0.74–0.94; p = 0.002 |
Antibiotic use in primary care within 12 months | 11% (1008/9579) | 9% (891/9540) | Multivariate risk ratio 0.85; 95% CI 0.77–0.93; p < 0.001 |
Consultation in primary care or hospitalisation with respiratory infection within 4 months | 11% (1021/9579) | 10% (951/9540) | Multivariate risk ratio 0.90; 95% CI 0.82–0.98; p = 0.014 |
Consultation in primary care or hospitalisation with respiratory infection within 12 months | 17% (1653/9579) | 16% (1527/9540) | Multivariate risk ratio 0.90; 95% CI 0.84–0.96; p = 0.001 |
Number of respiratory infections in household members | 49% (4193/ 8551) | 44% (3545/ 8075) | Multivariate risk ratio 0.88; 95% CI 0.85–0.92; p < 0.0001 |
Number of respiratory infections in the household at 4 months, M (SD) | 1.17 (2.07) | 0.93 (1.48) | Multivariate incident rate ratio 0.79; 95% CI 0.74–0.83; p < 0.0001 |
The Germ Defence intervention was successful at reducing incidence of RTI and transmission within the home [
9]. After 16 weeks, 51% of individuals in the intervention group reported one or more episodes of RTI compared with 59% in the control group (multivariate risk ratio 0·86, 95% CI 0·83–0·89;
p < 0·0001). The intervention reduced transmission of RTIs (reported within 1 week of another household member) both to and from the index person. It also reduced incidence of gastrointestinal infections from 25% in the control to 21% in the intervention (multivariate risk ratio 0.82, 95% CI 0.76–0.88;
p < 0.0001). The participants in the intervention group had less days of moderate or severe symptoms. These self-reported measures were confirmed by objective measures from medical notes: the intervention group were less likely to have had antibiotics prescribed, or to have had a consultation in primary care or hospitalisation with RTI, at both 4 and 12 months.
Two Chinese studies, Hu 2018 and Hu 2019, one which was at high risk of bias and one that had some concerns, reported that establishing a WeChat group could improve health outcomes related to HFMD [
17,
18]. Hu 2019 was an RCT, and reported that the WeChat intervention decreased the duration of the rash and led to faster recovery compared to a control group that only received the usual face-to-face GP care: duration of rash: intervention
M (SD) = 3.65 (0.8) days, control
M (SD) = 7.43 (1.9) days; time to recovery: intervention
M (SD) = 6.66 (1.5) days, control
M (SD) = 13.04 (2.6) days [
18]. Hu 2018 was a non-randomised but controlled trial, where a WeChat was established among parents and staff in a daycare setting. They reported that the incidence of HFMD decreased to 13.3% in the control and to 0 in the group that had the WeChat intervention [
17].
Behavioural outcomes
Six studies reported behavioural outcomes (see Table
4): [
9,
16,
17,
19‐
21]. They were all concerned with handwashing. Three trials measured hand washing via self-report, [
9,
16,
20], whereas two reported behaviour about handwashing without saying who took the measure [
17,
21], and one reported soap use ratio (amount of soap used divided by number of restroom users), [
19]. Five out of the six (all but Bourgeois 2008) reported that the interventions increased handwashing (or soap use as a proxy for handwashing) [
9,
17,
19‐
21].
Table 4
Summary of behavioural outcomes
| Likelihood of staying home during an infectious respiratory illness during the study | 39% (16/41) | 14% (5/35) | p = .02 |
Self-reported hand hygiene: |
Q1.a. (content of question not reported) | 93% (40/43) | 89% (50/56) | OR = 0.9 (0.2–4.4), p = .88 |
Q1.b. (content of question not reported) | 81% (35/43) | 84% (47/56) | OR = 1.2 (0.4–3.8), p = .75 |
Q1.c. (content of question not reported) | 86% (37/43) | 86% (48/ 56) | OR = 1.9 (0.5–7.6), p = .36 |
Self-reported cough etiquette: |
Q2.a. (content of question not reported) | 72% (31/43) | 68% (38/56) | OR = 0.7 (0.3–1.6), p = .37 |
Q2.b. (content of question not reported) | 86% (37/43) | 93% (52/56) | OR = 2.3 (0.5–9.6), p = .27 |
Q2.c. (content of question not reported) | 51% (22/43) | 28 (50% (28/56) | OR = 1.0 (0.4–2.5), p = .93 |
Q2.d. (content of question not reported) | 91% (39/43) | 98% (55/56) | OR = 5.7 (0.6–53.4), p = .13 |
Q2.e. (content of question not reported) | 70% (30/43) | 79% (44/56) | OR = 1.8 (0.6–5.1), p = .30 |
Q2.f. (content of question not reported) | 58% (25/43) | 59% (33/56) | OR = 1.1 (0.5–2.7), p = .81 |
| Proportion of children who mastered the correct way of washing hands | 76.67% (23/30) | 96.67% (29/30) | χ2 = 5.192, p < 0.05 |
Proportion of children who formed good habits of washing hands | 66.67% (20/30) | 96.67% (29/30) | χ2 = 9.017, p < 0.05 |
| Proportion who said they washed hands 10+ times per day at 4-month follow-up | 37.20% (3228/8667) | 52.73% (4361/8270) | OR = 1.96 (1.83, 2.10), p < 0.0001 |
| Soap use ratio (soap use divided by number of restroom users in the trial period) in the men’s restroom; seven intervention domains, each compared to the blank passive control (relative increase, %): |
Disgust | 0.317 | 0.348 (9.8%) | p = .001 |
Norms/ affiliation | 0.317 | 0.347 (9.6%) | p = .003 |
Status/identity | 0.317 | 0.343 (8.3%) | p = .012 |
Positive control | 0.317 | 0.343 (8.2%) | p = .010 |
Cue | 0.317 | 0.341 (7.7%) | p = .014 |
Comfort | 0.317 | 0.341 (7.5%) | p = .020 |
Knowledge of risk | 0.317 | 0.336 (6.0%) | p = .044 |
Knowledge activation | 0.317 | 0.33 (5.1%) | p = .093 |
Soap use ratio (soap use divided by number of restroom users in the trial period) in the women’s restroom; seven intervention domains, each compared to the blank passive control (relative increase, %): |
Knowledge activation | 0.651 | 0.711 (9.4%) | p = .001 |
Positive control | 0.651 | 0.708 (8.9%) | p = .002 |
Knowledge of risk | 0.651 | 0.706 (8.6%) | p = .003 |
Norms/ affiliation | 0.651 | 0.698 (7.3%) | p = .008 |
Status/identity | 0.651 | 0.692 (6.4%) | p = .021 |
Disgust | 0.651 | 0.683 (5.0%) | p = .0.78 |
Cue | 0.651 | 0.674 (3.5%) | p = .178 |
Comfort | 0.651 | 0.654 (0.6%) | p = .832 |
Study 2 | Number of times per day that new mothers washed their hands with soap at end of study (M) | 8.8 | 10.1 (Adj RR: 1.04) | p = .035 |
Number of times per day that mothers of 4–7 year olds washed their hands with soap at end of study (M) | 6.8 | 7.8 (Adj RR: 1.07) | p = .007 |
| Proportion of children who wash hands before eating and after going to the toilet at end of study | 71.7% (987/1376) | 93.6% (1300/1389) | χ2 = 231.07, p < 0.01 |
Proportion of children who wash hands after going out at end of study | 69.1% (951/1376) | 92.6% (1286/1389) | χ2 = 246.48, p < 0.01 |
Wu 2020 found that sending weekly text messages about prevention and treatment of HFMD to parents increased handwashing among children [
21]. It is not clear from the paper who took observations for the outcome measure or whether they were self-reported. One year after the start of the trial the proportion of children in the intervention group who washed their hands after going out was 92.6%, compared to 68.1% in the control, and the proportion who washed their hands before and after eating 1 year after the start of the intervention was 93.6% in the intervention group compared to 71.7% in the control (both
p < 0.01).
Sending weekly 90 s audio messages about hand hygiene to mothers in a relatively low-income area of India led to increased self-reported handwashing with soap at key occasions [
20]. Hand washing behaviour was measured 21 days after the end of the intervention, by putting stickers to represent handwashing occasions in a sticker diary, which had the day segmented into seven sections; participants also had to self-report some distractor activities, which were intended to mask the purpose of the study. There were two groups in the study, new mothers and mothers of four to seven-year olds, each with a comparable control group (who also had to own phones). New mothers were more likely to report washing their hands in the intervention than in the control group (Adj RR: 1.04,
p = .035), corresponding to 1.3 more occasions daily, and a 3.0 percentage point increase from a baseline rate of 49.6%. The mothers of four to seven-year olds were more likely to report washing their hands in the intervention group than the controls (RR: 1.07,
p = .007), corresponding to 1.0 more occasions daily, and an increase of 3.4 percentage points over a baseline rate of 46.7%.
In Hu 2018’s non-randomised but controlled trial using an interactive WeChat intervention, where health care workers could circulate educational materials and parents could ask questions, both the proportion of children who mastered the correct way of washing their hands and the proportion of children who formed good habits of washing their hands increased from 76.7 to 96.7% (both
p < 0.05) [
17]. It is not reported how the measurements were taken, or whether they were self-reports.
Putting electronic text-only messages on bulletin boards outside of English highway service station restrooms was effective at increasing soap use ratio (soap use/ per person entering the restroom) [
21]. Most of the seven intervention domains in Judah 2009 showed a small but statistically significant increase in soap-use ratio when compared with the blank passive control; however, the pattern of results was very different for men and women. Knowledge activation (reminders about the dangers of failing to wash hands) was the top-performing domain for women with a 9.4% increase compared with the blank control condition (
p = .001), but was ineffective for men. Disgust messages, which aimed to arouse a “yuck” response, led to the biggest improvement in men with a 9.8% relative increase compared with the blank control (
p = .001), but produced no significant response in women. Norms and status/ identity were effective for both genders, as was the positive control condition, “Wash your hands with soap”. There were two messages for each domain and the only individual message that was effective for both genders was the norms message, “Is the person next to you washing with soap?”, which resulted in a 12.1% relative increase in hand-washing ratio among men and a 10.9% increase among women compared with the control condition. This was the most effective message for men and the second most effective for women.
A trial in a US workplace, Bourgeois 2008, that sent tailored targeted messages about influenza illness and prevention over 16 weeks, via a personally controlled health record program, had mixed results, including no statistically significant improvement in handwashing [
16]. Participants in the intervention group were more likely to stay home during an infectious respiratory illness (self-reported) compared with participants in the control group, who received messages about cardiovascular care and sun protection (39% [16/41] vs 14% [5/35], respectively;
p = .02) There was no change in self-reported hand hygiene or cough etiquette.
Little 2015 found that self-reported handwashing was higher in the group that had received the Germ Defence intervention [
9]. The proportion of participants who reported that they washed their hands 10+ times per day was 52.7% in the intervention group, compared to 37.2% in the control, OR = 1.96 (1.83, 2.10),
p < 0.0001.