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Seasonal influenza vaccination (SIV) coverage among young children remains low worldwide. Mobile social networking apps such as WhatsApp Messenger are promising tools for health interventions.
This was a preliminary study to test the effectiveness and parental acceptability of a social networking intervention that sends weekly vaccination reminders and encourages exchange of SIV-related views and experiences among mothers via WhatsApp discussion groups for promoting childhood SIV. The second objective was to examine the effect of introducing time pressure on mothers’ decision making for childhood SIV for vaccination decision making. This was done using countdowns of the recommended vaccination timing.
Mothers of child(ren) aged 6 to 72 months were randomly allocated to control or to one of two social networking intervention groups receiving vaccination reminders with (SNI+TP) or without (SNI–TP) a time pressure component via WhatsApp discussion groups at a ratio of 5:2:2. All participants first completed a baseline assessment. Both the SNI–TP and SNI+TP groups subsequently received weekly vaccination reminders from October to December 2017 and participated in WhatsApp discussions about SIV moderated by a health professional. All participants completed a follow-up assessment from April to May 2018.
A total of 84.9% (174/205), 71% (57/80), and 75% (60/80) who were allocated to the control, SNI–TP, and SNI+TP groups, respectively, completed the outcome assessment. The social networking intervention significantly promoted mothers’ self-efficacy for taking children for SIV (SNI–TP: odds ratio [OR] 2.69 [1.07-6.79]; SNI+TP: OR 2.50 [1.13-5.55]), but did not result in significantly improved children’s SIV uptake. Moreover, after adjusting for mothers’ working status, introducing additional time pressure reduced the overall SIV uptake in children of working mothers (OR 0.27 [0.10-0.77]) but significantly increased the SIV uptake among children of mothers without a full-time job (OR 6.53 [1.87-22.82]). Most participants’ WhatsApp posts were about sharing experience or views (226/434, 52.1%) of which 44.7% (101/226) were categorized as negative, such as their concerns over vaccine safety, side effects and effectiveness. Although participants shared predominantly negative experience or views about SIV at the beginning of the discussion, the moderator was able to encourage the discussion of more positive experience or views and more knowledge and information. Most intervention group participants indicated willingness to receive the same interventions (110/117, 94.0%) and recommend the interventions to other mothers (102/117, 87.2%) in future
Online information support can effectively promote mothers’ self-efficacy for taking children for SIV but alone it may not sufficient to address maternal concerns over SIV to achieve a positive vaccination decision. However, the active involvement of health professionals in online discussions can shape positive discussions about vaccination. Time pressure on decision making interacts with maternal work status, facilitating vaccination uptake among mothers who may have more free time, but having the opposite effect among busier working mothers.
Hong Kong University Clinical Trials Registry HKUCTR-2250; https://tinyurl.com/vejv276
Seasonal influenza creates a substantial annual global disease burden. Young children are the most vulnerable age group [
Sending vaccination reminders through mobile phone–based short message services (SMS) has been shown to promote vaccination uptake, including routine immunization and SIV in children [
Existing vaccination reminders for promoting childhood SIV uptake have usually contained information on influenza infection risks and SIV benefits [
Studies in behavioral economics and neuroscience have suggested that introducing time pressure in decision making could increase decision makers’ reliance on heuristic cues for decision making, mainly through the mechanisms of acceleration (ie, switching to simpler strategies to speed up decision making) and selectivity (ie, automatically omitting certain information and favoring certain information) [
This preliminary study tested the effectiveness and parental acceptability of social networking interventions through the use of WhatsApp discussion groups for promoting children’s SIV uptake in Hong Kong. The specific objectives of this study were as follows:
Examine the effectiveness of regularly delivering vaccination reminders and encouraging sharing positive SIV decisions and experiences through WhatsApp discussion groups in promoting target children’s SIV uptake
Examine the effect of adding time pressure to parental SIV decisions (reminding parents about the remaining optimal SIV window)
Conduct content analysis of WhatsApp discussion posts during the intervention period to examine how participants responded to childhood SIV and their interactions with the group moderator through WhatsApp discussions
Examine acceptability to participants of using WhatsApp discussion groups as an example of social networking interventions for promoting child health
This study received ethical approval from the institutional review board of the University of Hong Kong/Hospital Authority Hong Kong West Cluster (reference number UW 17-003) and was registered with the Hong Kong University Clinical Trials Registry [HKUCTR-2250]. Participants were randomly allocated to either the control group, which received no intervention, or one of two social networking intervention groups that received weekly reminders to take their children for SIV via WhatsApp discussion groups with a time pressure component (SNI+TP) or without a time pressure component (SNI–TP) incorporated into the vaccination reminders. The intervention lasted for the 8 weeks of the Hong Kong government SIV campaign. Both intervention groups were also encouraged to share their positive vaccination decisions and experiences via their respective WhatsApp group with group members and a group moderator during the intervention period. A supermarket voucher valued at US $12.80 was given to every participant to improve response rate in the follow-up survey [
Since mothers in Hong Kong are the primary decision makers or significantly contribute to decision making with fathers for children’s immunization [
The vaccination reminder comprised three messages. Message 1 introduced the CIVSS and doctors’ recommendations for children’s SIV, message 2 addressed children’s risk of seasonal influenza and benefits and safety of SIV for children, and message 3 addressed the number of days remaining for the recommended vaccination timing (days remaining from the date when the vaccination reminder was sent out to the date 2 weeks before the winter influenza season). While the vaccination reminders for SNI–TP and SNI+TP contained message 1 and 2, message 3 (the time pressure component) was only included in the vaccination reminders for SNI+TP participants. All messages were constructed using information from the official websites of the Hong Kong Centre for Health Protection and World Health Organization and local published studies [
In addition to delivering weekly vaccination reminders, a WhatsApp discussion group was also set up to provide positive peer support for mothers to make better-informed SIV decisions regarding their children. To control group size and facilitate group discussion, participants allocated to the intervention groups were then randomly allocated to one of two SNI–TP and two SNI+TP WhatsApp discussion groups, each comprising approximately 40 mothers. In each WhatsApp discussion group, mothers could post their opinions and concerns about influenza and SIV and freely communicate with other mothers and the group moderator about their experiences of personal and child influenza vaccinations. The project moderator monitored and facilitated the group discussions on a daily basis following standardized guidelines (
In April and May 2018 after the winter influenza season, all participants were again contacted to report information on their children’s SIV uptake before and during the 2017-2018 influenza season. For participants who had more than one child eligible for CIVSS, the vaccination status of each eligible child was recorded. Mother’s intention to take their children for SIV in the next 12 months was also recorded. Risk perceptions regarding seasonal influenza and SIV for children were assessed again to examine whether any changes in perceptions occurred after the interventions. Participants’ opinions about the interventions and their willingness to receive vaccination reminders via WhatsApp in the future were asked to assess the acceptability of the interventions. In addition, a total of 20 participants from the intervention groups were contacted from May to July 2018 for in-depth interviews to explore their opinions about interventions and the acceptability of using WhatsApp for promoting children’s health.
Timeline and study procedure. CIVSS: Childhood Influenza Vaccination Subsidy Scheme.
Pearson chi-square tests were first conducted to compare participants’ demographics, baseline perceptions, history of influenza vaccination, and their target child’s characteristics by intervention arm to assess randomization and by follow-up status to assess selection bias.
Children’s SIV uptake rate in 2017-2018 was calculated for each group and compared between groups using the Pearson chi-square test. Both the SIV uptake of all target children aged between 6 to 72 months and that of the youngest target child’s SIV were compared across groups, because among families with more than one target child, the youngest one tends to be not vaccinated [
To further assess the effects of the interventions on vaccination uptake, a generalized estimating equation (GEE) logistic regression model was conducted to examine the following questions: (1) Did SIV outcome differ by intervention arm (intervention effect)? (2) Did SIV outcome change from baseline to follow-up (time effect)? (3) Did change of SIV outcome by time differ by intervention arm (intervention × time interaction)? GEE can accommodate cases with missing outcome measures at some time points (cases with outcome measure at one time point will be counted) and the correlation between the outcome measures at different time points (ie, the baseline and follow-up SIV uptake) [
In the GEE analysis, participants’ youngest target child’s SIV status during the follow-up period was used as the outcome. Since the final SIV uptake of the target child(ren) of participants who dropped out at follow-up was unavailable, intention-to-treat analysis was used as a conservative and sensitivity analysis by treating the lost outcomes as not vaccinated over the specific CIVSS campaign to compare with the complete case analysis.
Excepting for effects on children’s SIV uptake, intervention effects on parental perceptions regarding influenza and SIV by intervention arm were also assessed using chi-square and similar GEE logistic regression modeling. All WhatsApp group posts were archived by the project moderator immediately before the WhatsApp discussion groups were closed.
The mean number of posts per participant was calculated while the distributions of participants’ frequency of posting across discussion groups were compared using Kruskal-Wallis equality-of-populations rank tests. All discussion posts were examined to further explore participants’ responses to the vaccination reminders, their perceptions and attitudes regarding influenza and influenza vaccination, and how they interacted with peers and the group moderator during the communication process.
All posts were analyzed and coded by two researchers independently using content analysis. Each post was coded for the following categories: role (moderator or participant), format (text, picture, emoji, or hyperlink), cybersupport (eg, sharing views or experience and emotional exchange) and discussion topics (eg, vaccine effectiveness, vaccine safety, and side effects). More than one code could be assigned to each post. A coding scheme for cybersupport and discussion topics was drafted and developed by the first author based on literature on online psychosocial support [
The refined coding scheme was then used in NVivo 12.0 (QSR International Pty) by the first author and a trained research assistant to independently code all the posts again. The interrater agreement between the two coders was assessed; the Cohen kappa was less than 0.6, indicating low agreement, which was then resolved by joint discussion between the two coders.
How the moderator’s involvement in the WhatsApp discussion could change the discussion direction about SIV among participants was also analyzed by plotting the time sequence of cybersupport behaviors of participants and the moderator in each discussion group. Parental acceptability of the intervention was first assessed by describing participants’ opinions about the interventions and their willingness to receive vaccination reminders via WhatsApp in the future. In addition, thematic coding was conducted to identify themes and categories relating to parental acceptability of the interventions and using WhatsApp Messenger for child health promotion emerging from the in-depth interviews. All quantitative data were analyzed using Stata 15.1 (StataCorp LLC) while the textual data were analyzed using NVivo 12.0.
A total of 365 mothers in the control, SNI–TP, and SNI+TP groups completed the baseline assessment, of whom 85.9% (174/205), 71% (57/80), and 75% (60/80), respectively, completed the outcome assessment. Two participants of the SNI/–TP left the group in the first week of the intervention without giving any reasons and another 2 participants of the SIN/–TP left in the fifth week of the intervention for violating participation rules with offensive statements when arguing over SIV for their children. Participants of the intervention groups were more likely to drop out from the outcome assessment than were the control (χ222=8.0,
The youngest target child SIV uptake rates were 37.9% (66/174), 33% (19/57), and 38% (23/60) in the control, SIN–TP, and SNI+TP groups, respectively. Chi-square tests indicated that the interventions did not have significant effects on either the youngest target child’s SIV uptake or all target child(ren)’s SIV uptake (
GEE analysis was conducted to further take into account the time effect (SIV uptake rate changed from the baseline to the follow-up) and its interaction with the intervention condition as well as its interaction with both intervention condition and participants’ work status. Results showed that the youngest target child’s SIV uptake rate significantly increased from the baseline to the follow-up (OR 3.13, 95% CI 2.14-4.57) in all groups, but such increase was shown to be significantly less in the SNI+TP group than the control (OR 0.27, 95% CI 0.10-0.77) after adjusting for participants’ work status. Participants’ work status significantly interacted with both the time and intervention effects, with the target child’s follow-up SIV uptake increased significantly more among participants who did not have a full-time job than the control (OR 6.53, 95% CI 1.87-22.82;
Seasonal influenza vaccination uptake rates among target children at the follow-up by intervention condition.
Characteristic | Control (n=174), % (95% CI) | SNI–TPa (n=57), rate (95% CI) | SNI+TPb (n=60), rate (95% CI) | |||
SIVd, youngest target child | 37.9 (30.7-45.6) | 33.3 (21.4-47.1) | 38.3 (26.0-51.8) | .80 | ||
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.78 | ||
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All | 37.4 (30.2-45.0) | 33.3 (21.4-47.1) | 38.3 (26.1-51.8) |
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Partial | 4.0 (1.6-8.1) | 21.7 (0-9.4) | 21.7 (0-8.9) |
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Secondary or below | 37.1 (25.9-49.5) | 33.3 (15.6-55.3) | 46.7 (28.3-65.7) | .56 |
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Tertiary or above | 38.5 (29.1-48.5) | 33.3 (18.0-51.8) | 30.0 (14.7-49.4) | .66 |
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40,000 or below | 37.0 (27.1-48.0) | 20.0 (6.8-40.7) | 36.0 (18.0-57.5) | .27 |
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More than 40,000 | 38.8 (28.4-50.0) | 43.7 (26.4-62.3) | 40.0 (23.9-57.9) | .89 |
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Full-time | 37.6 (27.8-48.3) | 31.8 (13.9-54.9) | 16.7 (5.6-34.7) | .10 |
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Part-time/unemployed | 38.3 (27.7-49.7) | 34.3 (19.1-52.2) | 60.0 (40.6-77.3) | .07 |
aSNI–TP: social networking intervention group who received weekly vaccination reminders without time pressure component.
bSNI+TP: social networking intervention group who received weekly vaccination reminders with time pressure component.
c
dSIV: seasonal influenza vaccination.
Assessment of the intervention effects on child’s influenza vaccination uptake using generalized estimating equation logistic regression.
Independent variables | Beta (SEa) | Odds ratio (95% CI) | ||
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SNI–TPb (vs control) | –0.20 (0.38) | 0.82 (0.38-1.71) | .59 |
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SNI+TPc (vs control) | 0.24 (0.34) | 1.27 (0.65-2.47) | .65 |
Time effect: follow-up versus baseline | 1.14 (0.19) | 3.13 (2.14-4.57) | <.001 | |
Time × SNI–TP | –0.002 (0.51) | 1.00 (0.36-2.73) | .95 | |
Time × SNI+TP | –1.29 (0.53) | 0.27 (0.10-0.77) | .01 | |
Work status (part-time/unemployed vs full-time) | 0.14 (0.24) | 1.15 (0.72-1.83) | .56 | |
Time × SNI–TP × part-time/unemployed | –0.03 (0.60) | 0.97 (0.30-3.17) | .96 | |
Time × SNI+TP × part-time/unemployed | 1.88 (0.64) | 6.53 (1.87-22.82) | .003 |
aSE: standard error.
bSNI–TP: social networking intervention group who received weekly vaccination reminders without time pressure component.
cSNI+TP: social networking intervention group who received weekly vaccination reminders with time pressure component.
GEE analysis was also conducted to examine whether change in participants’ SIV perceptions from the baseline to the follow-up differed by intervention condition. Results showed that there were significant intervention effects on the change of participants’ perceived self-efficacy in taking children for SIV, with participants of the SNI–TP (OR 2.69, 95% CI 1.07-6.79) and SNI+TP (OR 2.50, 95% CI 1.13-5.55) groups reporting more increase in confidence in taking their children for SIV than did the control participants (
Change in participants' perceived self-efficacy for taking child for seasonal influenza vaccination by intervention condition. SNI–TP: group that received weekly reminders to take their children for SIV via WhatsApp discussion groups without a time pressure component; SNI+TP: group that received weekly reminders to take their children for SIV via WhatsApp discussion groups with a time pressure component; SIV: seasonal influenza vaccination.
From four WhatsApp discussion groups including two SNI–TP groups and two SNI+TP groups, after excluding posts irrelevant to influenza, vaccination, or children’s health (2.7% [12/446] of the total posts), 434 posts from participants were retrieved over 8 weeks, on average 13.6 posts per group per week. Overall, 58.1% (93/160) of the participants who joined the WhatsApp discussion groups participated in the online discussion, on average 3.08 posts (SD 5.90) per participant (Table C of
Of 434 participant posts, 226 (52.1%) were coded as sharing experience or views, 119 (27.4%) as seeking information or opinions, 106 (24.4%) as sharing knowledge or information, and 66 (15.2%) as emotional exchange (
Quotes about cybersupport from the WhatsApp discussion groups.
Cybersupport and number of posts | Quotation | ||
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Negative (101/226, 44.7%) |
I also do not take my child for flu vaccination because it can be worse if he got a fever after taking vaccination. I have to work and don’t want to take leave to take care of him (after vaccination). |
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Positive (87/226, 38.5%) |
I took my 3-year-old son for flu vaccination today. He also took the flu vaccination when he was two years old. I think it is necessary. Now, we cannot overlook the risk of influenza. In addition, the viruses change more and more easily. It is necessary to give children the prevention. We should take our children for the vaccination even if there is no subsidy from government. |
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Neutral/Mixed (39/226, 17.3%) |
I’m indecisive...Don’t know whether I should take my child for the vaccination. |
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Seeking information or opinions (119/434, 27.4%) |
I want to ask: it is my baby’s first flu vaccination. What can be the maximum time interval between the two doses of flu vaccine? Is it true that one has to take flu vaccination every year once he/she takes the first flu vaccination? |
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Sharing knowledge or information (106/434, 24.4%) |
There are still some quadrivalent influenza vaccines at Dr XXX in Yuen Long. The vaccination is free there. You may call the clinic for more information if your child hasn’t received the vaccine. They provide flu vaccination during weekends. |
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Emotional exchange (66/434, 15.2%) |
Thank you for sharing the information. I’m considering (whether to take my child for flu vaccination (or not) feeling uncertain. |
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Sharing knowledge or information (144/203, 70.9%) |
All children aged 6 months to 8 years who have never received flu vaccine or those who just received one dose of flu vaccine at their first-time vaccination should receive two doses of flu vaccine. |
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Encouraging information and experience sharing (42/203, 20.7%) |
Mothers who have taken your child for influenza vaccination can share your experience! |
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Encouraging vaccination planning (21/203, 10.3%) |
According to our survey, most parents indicated intention to take their children for flu vaccination. Mothers who have such intention are encouraged to plan your child’s vaccination early. |
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Encouraging information seeking (20/203, 9.9%) |
We understand that the people in the public have different opinions about influenza vaccination. We should carefully evaluate the evidence and the sources of the information. Surely, as a parent, you are the main decision maker for your child’s flu vaccination. You are encouraged to discuss with your family doctor if necessary. |
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Sharing experience or views (14/203, 6.9%) |
I remember, at the second time when I took my daughter to take flu vaccination, she cried out as soon as she saw the nurse. But, we can’t care too much about her crying because the vaccination can protect her from diseases. |
The main discussion topics among participants’ posts are shown in
Quotes from main discussion topics of participant posts (n=434).
Discussion topics and number of posts | Quotation | |
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Positive (69/134, 51.5%) |
I will take my child for flu vaccination. I also have booked an appointment to take my son for flu vaccination. |
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Negative (40/134, 29.9%) |
I won’t take my child for flu vaccination because there is still some negative news. |
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Being hesitant or seeking opinions for vaccination decision (25/134, 18.7%) |
I am considering (whether to take my child for flu vaccination). Then, should I take my child for flu vaccination? |
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Sharing information (48/63, 76%) |
Dr XXX at Kwai Fong, trivalent vaccine is free and quadrivalent vaccine cost HK$60. My child just took the vaccination yesterday, and they still have some available vaccines. |
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Seeking information (15/63, 24%) |
Which clinics provide free flu vaccination (for children)? |
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Concerns over vaccine safety and side effects (40/62, 65%) |
Is it true that one needs to take influenza vaccination every year once he/she receives the first flu vaccination and that all family members should receive influenza vaccination once one member of the family receives the flu vaccination (otherwise it can be worse)? |
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Being mixed or neutral/purely seeking information about vaccine safety and side effects (16/62, 26%) |
Different children may have different reactions to the flu vaccination. What can be the side effects of flu vaccination? |
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Sharing information for clarifying vaccine safety and side effects (6/62, 10%) |
It is misinformation that vaccination can cause autism. This rumor has been dismissed many years before. |
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Concerns over vaccine effectiveness (26/51, 51%) |
Now there are too many viruses/bacteria, and they change very quickly. This time, we take the flu vaccination against this virus but later another new virus emerges. How can we ensure that the vaccination is effective? It depends on how accurate their guess on the vaccine strain is every year. If their guess is wrong, the flu shot is a meaningless suffer. If one can still get sick even after taking the vaccination, why should he suffer from an injection? |
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Sharing information for clarifying vaccine effectiveness (16/51, 31%) |
Although there is mismatch, the vaccine is still effective for preventing influenza H1N1 or influenza B viruses. It (flu vaccination) is an additional protection for our children. |
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Being mixed or neutral/purely seeking information about vaccine effectiveness (15/51, 29%) |
Is it true that one can still get a cold even after taking the vaccination but can protect against influenza? Can influenza vaccination protect one against serious complications due to influenza? |
Medical eligibility for seasonal influenza vaccination (40/434, 9.2%) |
I thought to take my daughter for flu vaccination today but she has a running nose and some cough. Is it OK for her to take flu vaccination? |
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Positive (16/33, 49%) |
My child has taken the flu vaccination and he still feels very good now. |
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Negative (12/33, 36%) |
My elder daughter took the flu vaccination once but got more and severe sicknesses that year. Since then, she has never taken flu vaccination... |
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Mixed or uncertain (5/33, 15%) |
My two sons have taken the flu vaccination. One is 3 years old. He was given injection in the hip and he said no pain. Another is 7 years old. He was given injection in the arm. He said it was very painful and the pain lasted for 2 days. |
Doubtful or negative vaccination attitudes (26/434, 6.0%) |
Vaccination is to inject germs into the body. Is it necessary to take flu vaccination if my child is always healthy? Too many vaccinations are not good for children. |
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First-time influenza vaccination (20/434, 4.6%) |
I would like to ask: it is my baby’s first flu vaccination. The doctor said he needed two doses of vaccines. Then what’s the maximum time interval between the two vaccinations? |
The main knowledge and information shared by the moderator was about vaccine effectiveness (30/144, 20.8%), vaccination clinic and cost (27/144, 18.8%), vaccine safety and side effects (25/144, 17.4%), medical eligibility for SIV (18/144, 12.5%), and first-time influenza vaccination (15/144, 10.4%). The moderator also provided social cues related to vaccination (eg, doctors’ recommendation, other mothers’ decisions to take their child for SIV, and vaccination statistics) to motivate vaccination decision or planning (23/144, 16.0%).
To illustrate the change of participant cybersupport behaviors as the moderator became involved in the online discussion, participant cybersupport behaviors were categorized into three types based on their potential effects on SIV uptake: positive cybersupport behaviors comprising sharing positive experience or views, sharing knowledge or information and positive emotional exchange; negative cybersupport behaviors comprising sharing negative experience or views and negative emotional exchange; and mixed or neutral cybersupport behaviors comprising sharing mixed or neutral experience and views, seeking information or opinions, and other emotional exchange.
Change of cybersupport behaviors among participants by time and moderator’s involvement. SNI–TP1 and SNI–TP2: groups that received weekly reminders to take their children for SIV via WhatsApp discussion groups without a time pressure component; SNI+TP1 and SNI+TP2: groups that received weekly reminders to take their children for SIV via WhatsApp discussion groups with a time pressure component; SIV: seasonal influenza vaccination.
Of the 117 participants of the intervention groups who completed the outcome assessment, 115 (98.3%) reported reading the discussion posts at least several times a week during the intervention period and 105 (89.7%) had read more than one-half of all discussion posts. Over 80% (95/117, 81.2%) indicated no concern over participating in the WhatsApp discussion groups. Of those expressing concerns, the most common concern was receiving misinformation or irrelevant information. Most (93/117, 79.4%) agreed that the information from the discussion groups could improve understanding about SIV. Around 60% (70/117, 59.8%) agreed that the information was useful but 20.0% (23/117) reported the information was insufficient for SIV decision making. Overall, 94.0% (110/117) were willing to accept the same intervention in the future, 84.6% (99/117) would recommend the intervention to other mothers, and 87.2% (102/117) were satisfied with the moderator’s information.
Post hoc qualitative interviews with 20 participants of the intervention groups were analyzed to clarify participants’ in-depth opinions about the interventions (Table D of
This social networking intervention, involving sending weekly vaccination reminders and encouraging exchanges of positive experiences and information among participants via WhatsApp discussion groups during an influenza vaccination campaign, did not significantly enhance children’s SIV uptake. Two main reasons may explain why a significant effect of sending regular vaccination reminders was not identified. First, compared with previous studies that used vaccination reminders to promote routine childhood immunization [
Despite not increasing SIV uptake among the target children, the social networking intervention was significantly effective for promoting mothers’ self-efficacy in taking their children for SIV. This is possibly due to the frequent posts of information about the vaccination clinics and cost that were shared by both moderator and participants through the online discussion. Previous studies also have found that online information support significantly increased parents’ perceived self-efficacy in other child health care practices [
Including an additional time pressure did not significantly enhance childhood SIV uptake. However, subgroup analysis showed that children’s SIV uptake significantly increased among mothers without a full-time job while declining slightly among mothers with a full-time job when the time pressure intervention was included. The qualitative data indicated that time pressure pushed participants to make a rapid decision, but those decisions can be either positive or negative. Unemployed and part-time-employed mothers may have more cognitive resource to deliberate the pros and cons of influenza vaccination and perceive that they have the ability to make the decision within time limit. Therefore, under some time pressure, they may become more active in searching information to reduce the risk of influenza and efficiently integrate different cues to reach a positive vaccination decision. In comparison, working mothers face more pressure from work for childcare [
The content analysis of the WhatsApp discussion identified several maternal concerns and misperceptions about SIV. Two common concerns about vaccine side effects were that SIV was needed annually once initiated and that all family members should be vaccinated if one member was vaccinated. These concerns seem linking to beliefs that SIV weakens immunity. This may be a misinterpretation of current recommendations for annual SIV vaccination of all family members which should be addressed in future SIV risk communications. Similarly, vaccine effectiveness was an issue because SIV does not ensure 100% protection and is worse where the SIV strain does not match the actual circulating strain. SIV was perceived to be useless or wasteful by participants. This may also link to a common distrust about how vaccine strains are predicted by the vaccine scientific committee. Future risk communication should clarify the accuracy of existing prediction for the main influenza vaccine strain and the effectiveness of SIV in protecting against not only risk of getting influenza but also complications of influenza illnesses, and even when strains are not matched, SIV can still offer some cross-immunity. Some participants refused SIV due to their belief that vaccination is not a natural process. Future risk communication should give a clear explanation about the mechanism of influenza vaccination, which is a quasi-natural process, by emphasizing similarities in vaccination and natural exposures to specific immunogens—the former is simply a controlled variant of the latter. For parents intending to take their children for SIV, information about medical eligibility for SIV, vaccination clinic and costs and how to arrange, particularly the timing of the two vaccinations for children’s initial SIV, should be provided to enhance optimal timing of SIV.
Despite being ineffective for increasing children’s SIV uptake, the intervention was nonetheless highly acceptable for most participants. They appreciated the convenience of using WhatsApp messenger as a channel for health communication compared with sourcing information from websites or other traditional health communication methods. In addition, participants emphasized the importance of being able to interact with a health professional and thereby have access to more professional, trustworthy, and personalized information through WhatsApp. This indicates that the involvement of a health professional in the online communication is highly valued by parents and is likely to have greater impact if the health professional is a primary care provider to the target population. However, our study also indicates that audience segmentation, based on parents’ prior beliefs about SIV, is necessary for improving the effectiveness and acceptability of social networking interventions to achieve behavioral change. Putting people with different vaccination beliefs into one group may lead to strong arguments which may negatively affect other members’ participation in the discussion and the online communication environment. Finding approaches that work to bring resistant parents around to SIV requires further research.
This study had several limitations. First, we only recruited participants who were users of WhatsApp or those who were willing to install WhatsApp on their mobile phone and thereby the sample may not be representative for the target population, although the penetration rate of WhatsApp use was very high in the population. Since almost all participants reported using WhatsApp on a daily basis, the data did not have sufficient variance to allow for examining the intervention effects stratified by WhatsApp use. Second, a discussion group specifically for influenza vaccination may dissuade those uninterested in the topic, causing in-group biases. However, our analysis did not find significant differences in participants’ demographics, perceptions of SIV, and SIV history and intention across intervention arms. Third, this was a preliminary study to test social networking interventions effects on SIV uptake and as such the sample size was insufficient for detecting a small effect size. Fourth, data on children’s SIV uptake were reported by parents and could not be validated from children’s medical records and may be subject to social desirability bias. The survey was emphasized to be anonymous for participants to minimize social desirability bias and improve response rate. Fifth, in the WhatsApp discussion groups, out-of-office-hour discussions were not promptly monitored and addressed. The time lag in addressing participants’ questions or concerns may have affected participants’ subsequent participation in discussions and thereby SIV decision making. However, it is difficult to determine optimal moderator input in the WhatsApp discussion given the discussion group tried to encourage mutual support between participants. Furthermore, the infrequent emotional exchange among participants also indicated insufficient development of attachment to and friendships between group members, which could be a reason for why around half of the participants were lurkers, silent and passive members in the WhatsApp discussion. This represents to be a big challenge for the sustainability of online discussion. Future studies need to examine how to encourage information support from peers, moderate their emotional interactions, and the optimized moderator participation.
The social networking intervention for mothers was ineffective for increasing SIV uptake among young children but did effectively increase mothers’ perceived self-efficacy for taking their children for SIV. A combination of social networking intervention with added time pressure on decision making can significantly promote children’s SIV among non–full-time working mothers, but among mothers working full-time, time pressure may reduce SIV uptake by reinforcing the influence of negative cues on SIV decision making. Future social networking interventions should consider audience segmentation using mothers’ working status and their prior SIV attitudes. Mothers’ participation in the online discussion mainly involved sharing concerns or negative views about vaccine safety, side effects, and effectiveness and seeking information or opinions to clarify these concerns. Mothers’ knowledge sharing and information giving was mainly supportive of those intending to take their children for SIV but seldom addressed concerns about vaccine safety, side effects, and effectiveness, possibly due to uncertainty around knowledge and information. The moderator played an important role by providing knowledge and information that addressed vaccine-related concerns and shaped positive online discussions about vaccination. Finally, our study indicates that WhatsApp messenger is a highly acceptable medium for health communication among parents in Hong Kong, but health professionals should be involved for more effective health communications.
Vaccination reminders (English and Chinese versions).
Guideline for monitoring and facilitating WhatsApp discussion for the moderator.
Supplementary tables.
Change of child's seasonal influenza vaccination uptake by intervention condition and participants' work status: (A) mothers with a full-time job and (B) mothers without a full-time job.
CONSORT EHEALTH checklist (V 1.6.1.).
Childhood Influenza Vaccination Subsidy Scheme
generalized estimating equation
seasonal influenza vaccination
short message service
group that received weekly reminders to take their children for SIV via WhatsApp discussion groups with a time pressure component
group that received weekly reminders to take their children for SIV via WhatsApp discussion groups without a time pressure component
This work was funded by a grant from the Hong Kong Government’s Health Medical Research Fund (grant number 16150752).
None declared.