Parental knowledge about respiratory syncytial virus (RSV) and attitudes to infant immunization with monoclonal antibodies

ABSTRACT

Background

Ninety percent of children are infected with respiratory syncytial virus (RSV) within their first two years of life. RSV is the main cause behind hospitalization of infants with lower respiratory tract infections. A new monoclonal antibody (mAb) immunization may prevent RSV in all infants. This cross-national study aimed to examine parental knowledge about RSV and attitudes to such RSV immunization.

Research design and methods

Based on a literature study, a questionnaire was designed and applied in a survey carried out in China, France, Germany, Italy, Japan, Spain, the UK, and the US. Eligible respondents were expecting their first baby or parents of children <24 months old who were open to vaccination.

Results

Parental acceptance of immunizations relies on perceptions of the preventable disease. In 5627 parents, only 35% reported basic or good level of knowledge about RSV. Recommendation from health care professionals and inclusion in immunization programs were crucial to their acceptance of RSV immunization. If recommended and informed about its efficacy and safety, most parents would accept RSV mAb immunization for their infants.

Conclusions

Infant RSV infections are highly prevalent, yet parental awareness of RSV is poor. Country variations call for targeted communication about RSV and immunization.

Plain Language Summary

Almost all children (90%) are infected with respiratory syncytial virus (RSV) before the age of two. Most cases of RSV are mild, but RSV remains the main cause behind hospitalization of infants with lung infections, such as bronchiolitis and pneumonia. A new immunization with monoclonal antibodies (mAbs) is currently being developed to prevent RSV in infants. While traditional vaccines act to mobilize a person’s own production of antibodies to fight a virus, immunization with mAbs means that antibodies are given directly. We know that parents’ attitudes to childhood vaccination depend on their views on childhood diseases and vaccination in general. Therefore, we wanted to examine what parents know about RSV. How widespread and severe do parents think RSV infection is? Would they like their infants to receive RSV immunization? To answer these questions, we carried out a survey in eight Western and Asian countries. More than 5000 people who were either expecting their first baby or already parents of under two-year-olds answered the questionnaire. Their responses showed that awareness of RSV was poor as two-thirds of parents had never heard of RSV or knew only the name. Once exposed to information about a hypothetical immunization against RSV disease, the immunization was considered beneficial; however, recommendation from health care professionals and inclusion in immunization programs were crucial to the parents’ ultimate acceptance of RSV immunization. If recommended and well informed about its safety and efficacy, most parents would accept mAb immunization against RSV for their infants.

KEYWORDS:

• Acceptability
• bronchiolitis
• immunization
• information needs
• monoclonal antibodies
• parents/parental
• respiratory syncytial virus (RSV)
• childhood vaccination

1. Introduction

Respiratory syncytial virus (RSV) is a common respiratory pathogen that causes disease throughout life but may be particularly severe in infants less than one year of age. RSV is the main cause of lower respiratory tract infections (LRTI) in children. RSV infections account for 60–80% of infant bronchiolitis, and up to 40% of pediatric pneumonias [1]. Ninety percent of children are infected with RSV in their first two years of life, and up to 40% of these will develop an LRTI with the initial episode, typically within the child’s first RSV season [2–6]. The RSV season lasts approximately five months from November through March in temperate regions.

Although most cases of LRTI are mild, RSV remains a leading cause of infections requiring hospitalization of infants [7]. Up to 79% of RSV-related hospitalizations are in previously healthy infants born at term [1,7–11]. A multi-center study from the US showed that 35% of children <5 years old who were hospitalized with acute respiratory illness tested positive for RSV. Of these, 87% were <24 months old and 50% were <6 months old [10,12]. US surveillance data has shown RSV-related pneumonia to be the most common viral cause of deaths in infants <1 year of age [13]. In Europe, annual incidence of RSV-related acute LRTI in hospitalized infants <1 year old is estimated to range from 10 to 28 per 1,000 children with some country variation [14–19]. A recent systematic review estimated that globally, RSV-related acute LRTI in infants <6 months results in 1.4 million hospital admissions, of which 184,000 are in industrialized countries, and 27,300 in-hospital deaths, mainly in developing countries [2]. Hospitalization may include intravenous fluids, intubation, and/or mechanical ventilation. Natural RSV infection only provides short-term immunity, making new infections common the following season [3].

So far, only a small subset of infants such as premature babies born at <35 weeks gestational age or those born with congenital heart or chronic lung disease have been offered immunization with palivizumab, a monoclonal antibody (mAb) requiring monthly injections throughout the RSV season. The World Health Organization (WHO) acknowledges that new RSV prevention strategies are needed [20]. A long-acting mAb designed to protect all infants <12 months old against RSV-related LRTI for the entire RSV season with a single dose is currently being investigated [21]. Routine immunization of all infants against RSV with a mAb is a new concept calling for an examination of parental attitudes to this novel prophylactic solution.

The primary aim of the present study was to examine parental awareness of RSV, and attitudes to the idea of routine immunization of infants with a mAb against RSV in eight countries across Asia, the US, and Europe. Secondarily, and for context, we aimed to examine parental attitudes to childhood immunization, in general, and main information sources regarding children’s health. This paper reports key results across regions.

2. Methods

A literature study was carried out in 2020 and included searches (completed in November 2020) focusing on a) parental attitudes to childhood vaccination; b) parental knowledge about RSV; c) parental knowledge of mAbs; and d) parental information needs regarding childhood vaccination (Appendix A: literature search strategy). The main aim with the literature study was to form the basis of the design of a survey questionnaire, i.e. to ensure the validity of questions and response options. In brief, the questionnaire included an introduction and initial screening questions, and then three main sections focusing on 1) Parental attitudes to childhood immunization and information sources, 2) Parental perceptions of RSV and bronchiolitis, and 3) Parental reactions to information about a new RSV immunization for all infants using mAbs. The questionnaire included three brief information boxes to allow for an assessment of parents’ reactions to information about RSV, immunization against RSV, and mAb technology (full questionnaire in Appendix B).

The questionnaire was completed online by parents in (in alphabetical order) China, France, Germany, Italy, Japan, Spain, the UK, and the US from March 18 to May 21, 2021. A panel approach was used wherein online survey panel members were invited to participate if meeting the inclusion criteria. The aim was to include 750 respondents in each of the five European countries and the US, 400 in China and 600 in Japan. Sample sizes were set lower in the Asian countries as research panels are less ingrained here. Overall, the sample size was designed to achieve a balance between margin of error (3.5% to 4.8% in any country) and feasibility of reaching respondents using the panel approach. These sample sizes enabled subgroup comparison using standard t-test for proportions and z-test for means, both for 95% confidence. The sample comprised an equal dispersion of ‘New’ parents (who were expecting their first child or had just one child under 24 months of age) and ‘Experienced’ parents (who had more than one child, at least one of whom was younger than 0–24 months old). This distinction enabled comparison between perceptions of RSV and immunization across these two groups.

Eligible respondents stated to have given or plan to give their child/children all, most (more than half) or some (less than half) of the childhood immunizations in the national immunization program. In this paper, we use the term ‘immunization’ to include active as well as passive immunizations – with active immunization referring to traditional vaccinations, while mAb is a type of passive immunization. Parents who had not given nor planned to give their children any childhood immunizations – or who stated to be uncertain of this – were excluded as these were likely hesitant toward any childhood immunization. This choice was made to avoid biasing results pertaining to RSV immunization, specifically.

As panel members, they had previously agreed to being contacted, but always had the option of declining participation in any survey without consequences. They were informed about this study being funded by a pharmaceutical company, that they had the right to withdraw at any time, and their responses would only be analyzed at an aggregated level and treated with confidentiality. The respondents gave their consent to participate on this basis. No personal information was collected except for information the participants disclosed in the survey. Ethics committee approval was not required.

3. Results

The literature showed that parental attitudes toward childhood vaccination are linked to perceived gains and losses of vaccination, including the perceived risk and severity of the vaccine-preventable disease (VPD), the options of treating the VPD, and other means of prevention, if any. A range of socio-cultural, emotional, spiritual, economic, and political factors have been shown to affect parental attitudes to vaccination [22–32]. Vaccine hesitancy is therefore subject to change across time, settings, and specific vaccines [26,30,31]. Also, relationships with health care professionals (HCP), information sources, and strategies, as well as vaccine accessibility are decisive to parental attitudes toward childhood vaccination [33–37]. Finally, the literature search found few studies regarding parental experiences and distress related to having children hospitalized with RSV, bronchiolitis, or more broadly with acute respiratory illness or LRTI [38–44]. Overall, it was shown that while parents may recognize symptoms and transmission of respiratory illness, in general, they lack knowledge about RSV specifically [38–41]. Parents aware of RSV were mainly those whose children had been hospitalized and/or received RSV prophylaxis [38,42–47]. Sources of information were HCPs and people whose children had RSV or received RSV prophylaxis [38]. The limited research on parental perceptions of mAbs focused on compliance with palivizumab [46–50]. The literature study led to the formulation of the survey questionnaire, including questions about awareness of RSV and bronchiolitis, perceptions of the severity and risk of RSV, and attitudes toward infant mAb immunization against RSV.

3.1. Parental attitudes to childhood immunization

A total of 5969 parents responded to the survey request of which 5627 were eligible to participate and completed the full survey: 2824 New and 2803 Experienced parents (overview of participant characteristics in Appendix C).

Of the 5969 initial respondents, 74% had given their infants ‘all recommended childhood immunizations in the routine immunization program’ so far, 15% had given ‘most,’ and 5% ‘some’ of the recommended immunizations. Six percent was uncertain or had not given their child any immunizations and were screened out. When asked about their intentions toward future immunizations, 83% planned to give their children all immunizations, 13% most, and 2% would only give some (country-specific details in Appendix D).

The three main reasons given for receiving childhood immunizations across countries were a) ‘to protect my child against preventable childhood diseases,’ b) ‘some childhood diseases are severe,’ and c) ‘I might regret if my child gets a childhood disease.’ The three main reasons for not wanting all recommended childhood vaccines were a) ‘worries about safety of immunizations,’ b) ‘children receive too many immunizations,’ and c) ‘lacking recommendation from HCP.’ Across countries, ‘conversations with HCP’ were the most frequently mentioned source of advice regarding health-related child issues. Pediatricians were the most frequently mentioned type of HCP, followed by a primary care physician (PCP) or nurse. In Germany, Japan, and the UK, midwives also played an important role. Following HCP, New parents, in particular, took advice from friends and family in Europe, Japan, and the US (detailed information sources in Appendix E).

3.2. Parental perceptions of respiratory syncytial virus (RSV) and bronchiolitis

3.2.1. Parental awareness of respiratory syncytial virus and bronchiolitis

Compared with other common childhood diseases (common cold, influenza, pneumonia, gastroenteritis, bronchiolitis, strep throat, LRTI, and roseola) respiratory syncytial virus (RSV) was the least well known. Only a third of respondents (35%) reported having ‘basic information’ or ‘good level of knowledge’ of RSV; 36% stated to ‘have never heard of it,’ and 29% had ‘heard the name but nothing else’ (Figure 1). In all countries except France, awareness of RSV, i.e. parents stating to have a basic or good level of knowledge, was significantly higher in Experienced compared to New parents (45% and 30%, respectively, P < 0.001). Please find country-specific RSV awareness in Appendix F.

Figure 1. Self-reported knowledge about respiratory syncytial virus (RSV) and bronchiolitis.

Awareness of bronchiolitis was comparatively higher, with 71% reporting to have ‘basic information’ or ‘good level of knowledge’ about this. In Japan, reported knowledge was significantly lower than in the other countries (38% vs. 75% across other countries, P < 0.001). Across regions, 8% had never heard of bronchiolitis and 21% knew only the name. Overall, significantly more Experienced parents felt informed about bronchiolitis than did new parents (76% vs. 66%, P < 0.001).

3.2.2. Parental perceptions of infant RSV infection before and after receiving information

Before being presented with information about RSV (Information 1), parents who reported being aware of RSV – i.e. those reporting a basic or good level of knowledge – were asked to state their concerns in relation to RSV and other common respiratory diseases affecting infants (pneumonia, influenza, common cold, LRTI, and bronchiolitis). Pneumonia was the most concerning disease; most parents considered it very severe for their infants, followed by RSV, then LRTI and bronchiolitis. This ranking was similar across countries. After receiving information about RSV, almost half of parents previously aware of RSV remained highly concerned about their child getting RSV. The number of highly concerned parents increased in China, the UK, and the US, remained the same in Japan, and decreased in the remaining European countries (Appendix G). The main causes for concern were ‘how common RSV is’ (main cause in China, the UK, and the US) and ‘the possible impact of disease’ (main cause in Japan and continental Europe).

Information 1. Information presented to respondents about respiratory syncytial virus (RSV).

Respiratory syncytial virus (RSV) is a common seasonal virus that infects nearly all children (90%) within their first two years of life. RSV is contagious and is transmitted through oral or nasal secretions. In infants 12 months and younger, mild, cold-like symptoms may include congestion, cough and decrease in appetite. However, many will develop a lower respiratory tract infection (bronchiolitis or pneumonia), and in rare cases, medical intervention is needed to regulate breathing. RSV is the most common cause of hospitalization for lower respiratory tract infection (LRTI) in young children. It is difficult to predict which babies will become severely ill, and most babies who are hospitalized due to RSV are otherwise healthy and were born full-term. Options for Prevention and Treatment • Currently, only very premature babies or babies born with conditions such as chronic lung disease or congenital heart disease receive immunization against RSV. This requires monthly injections throughout the typical five-month RSV season. There is no immunization against RSV for healthy babies. • The risk of RSV illness may be reduced – but not eliminated – by washing an infant’s toys, clothes, and bedding often, as well as washing hands before touching an infant. • There is no actual cure for RSV disease; treatment consists of symptom relief and supportive care. • Natural infection does not provide immunity, so it is possible to have more than one RSV infection in the same season. At a Global Level Globally, roughly one in every 160 children younger than five years who develop acute lower respiratory infections (LRTI) caused by RSV will die. The majority of deaths occur in developing countries

Before reading the information about RSV, most parents aware of RSV did not perceive the risk of infants contracting RSV to be high. Almost twice as many considered that RSV would be very severe to their infant (Table 1: ‘before info’). After reading the information about RSV, parental perceptions of the risk of their infant contracting RSV increased, overall, while perceptions of its severity decreased (Table 1: ‘after info’). In other words, parents came to understand how common RSV is, but also that it is mild in most cases.

Table 1. Parental perceptions of the risk and severity of RSV infection before and after receiving RSV information.

	Perceived Risk of Contracting RSV						Perceived Severity of RSV
	Low		Moderate		High		Mild		Moderate		High
	Before info	After info	Before info	After info	Before info	After info	Before info	After info	Before info	After info	Before info	After info
Assessment•
USA %	19	13	53	55	28	32	8	9	48	56	44	35
Europe %	19	12	60	65	21	23	4	7	49	66	47	28
Japan %	11	3	66	72	23	25	9	7	68	73	24	20
China %	7	3	48	44	45	53	2	1	38	32	60	67
Total %	16	10	58	62	26	28	5	7	49	61	46	33

*Assessments of risk and severity of RSV refer to responses to a 1–7 scale: Low risk/mild severity = responses 1–2. Moderate risk/severity = 3–5. Very high risk/very severe = 6–7. It should be noted that only parents who had stated to be aware of RSV were asked about their perceptions of risk and severity of RSV prior to receiving the RSV information. All respondents were asked about their perceptions of the risk and severity of RSV following the information.

3.2.3. Information sources about RSV and bronchiolitis

To parents stating to have a basic or good level of knowledge about RSV and bronchiolitis, HCPs were the main source of information. Experienced, American, and Chinese parents tended to mention a broader range of information sources about RSV compared to New parents and European and Japanese parents. In China, Europe, and Japan, 10–15% and 22% in the US knew about RSV from knowing ‘people whose child(ren) had had an RSV infection.’

Across regions, some parents knew about RSV because one of their own children had a case of RSV diagnosed by an HCP (8% a mild case and 6% a severe case). Some became aware of bronchiolitis because one of their children was diagnosed with it (11% mild; 6% severe cases) (details in Appendix H). Of parents whose child was diagnosed with bronchiolitis, 54% were told the cause. Significantly more were told in the US (76%) compared to China (63%, P = 0.027) and Europe (46%, P < 0.001).

3.3 Parental reactions to information RSV immunization with mAbs

To examine reactions to a new mAb immunization that may prevent RSV-related disease in all infants, respondents were presented with brief information about ‘product X’ (Information 2). It was stressed that the information was hypothetical, and when answering, respondents should assume this immunization was approved by local health authorities and their infant child was eligible to receive it.

Information 2. Information presented to respondents about a new immunization against RSV.

Product X Product X is the first immunization to prevent RSV disease in all infants. It provides protection for the entire RSV season (from autumn to spring) with one injection in a muscle. In a recent global clinical trial, one dose of Product X, given before the RSV season, offered healthy preterm infants protection against RSV disease throughout the RSV season. 70% of these infants were protected from lower respiratory tract infection (LRTI) due to RSV; and 78% were protected from risk of hospitalization with RSV-related LRTI. Clinical trials have proven Product X to be very safe with few adverse reactions, comparable to placebos. Product X has received the following designations from regulatory agencies: • Shown in the US: US Food and Drug Administration: Breakthrough Therapy • Shown in France, Germany, Italy, and Spain: European Medicines Agency: ‘PRIME’ designation • Shown in the UK: UK Medicines and Healthcare Regulatory Agency: Promising Innovative Medicine’ designation • Shown in China: China Center for Drug Evaluation: Breakthrough Therapy • Shown in Japan: Japan Agency for Medical Research and Development (AMED): ‘A product of high priority’

After receiving the information, 50% of respondents believed that this hypothetical immunization would be highly beneficial to their infant child (6–7 on a 1–7 scale), 46% moderately beneficial (3–5), and 3% not beneficial (1–2). In the information text, the parents were asked to highlight which aspects of it, if any, they found positive and/or negative, i.e. advantageous or disadvantageous to their infant. In Japan, the most frequently marked positive aspect was protection from RSV-related hospitalization; in all other countries, protecting infants for the duration of the RSV season was the key positive. Surprisingly, ‘few adverse reactions’ was the most frequently marked negative aspect in Europe and the US, which may be explained with higher expectations of safety. In China, the key negatives were ‘78% protected from risk of hospitalization with RSV-related LRTI’ and ‘70% protected from RSV-related LRTI’ which may suggest higher expectations of efficacy. In Japan, one of the key negatives was ‘protection for the entire RSV season,’ perhaps indicating higher expectations of durability. These attempted explanations are entirely hypothetical, however, as the survey did not allow respondents to argue for the reasons behind their answers.

If recommended as part of the immunization program and by the infant’s HCP, 60% of respondents considered there was a high chance they would accept ‘product X’ for their infant (8–10 on a 1–10 scale) (Figure 2). Acceptance rates were highest in China and lowest in France and Japan, where half the parents said there was a moderate chance (3–7). In total, 4% considered there was no or low chance (0–2) they would accept. Overall, European, Japanese, and Experienced parents were more hesitant toward a new immunization and their acceptance relied more on HCP recommendation and inclusion in the routine immunization program compared with Chinese, the US, and new parents.

Figure 2. Parental acceptance of infant immunization against RSV.

Question: ‘If Product X were recommended as part of the immunization programme and by your infant child’s healthcare professional, how likely would you be to accept this RSV immunization for your infant child?’ Responses on a scale of 0–10 where 0 = ‘No chance/almost no chance’ and 10 = ‘Certain/practically certain’ to accept: red (0–2) = low chance; yellow (3–7) = some chance; green (8–10) = high chance.

The main reason to accept this new immunization was a wish to protect one’s infant child against RSV. The main reason that parents might be hesitant was concern about potential side effects. Some also voiced concerns about the novelty of this immunization (Appendix I and J). This was mostly consistent between New and Experienced parents. The parents stated that the most important information about this RSV immunization, if available, regards its safety, and secondly, its efficacy.

Very few respondents reported having knowledge about ‘passive immunization’ (6.8%) and monoclonal antibodies or mAbs (3.1%). Receiving information about mAbs and passive immunization (Information 3) had a positive impact on 59% of parents’ willingness to let their infant receive ‘product X’ (5–7 on a 1–7 scale). The information had particularly positive impact in China (90%) and the US (68%). The information had no impact (4) on 33% of parents and negative impact (1–3) on 8% of parents. Germany and Japan saw the highest number of parents stating that the information had no or negative impact.

Information 3. Information given about passive immunization and monoclonal antibodies (mAbs).

Please read the information below, which explains how Product X works vs. some other immunizations. There are two types of immunization: active and passive. Current childhood immunizations are defined as ‘active immunizations.’ Active immunization works by activating the immune system to produce antibodies, which protect the body from a specific infectious disease. It can take days to weeks to develop this protection. ‘Passive Immunization’ with monoclonal antibodies (mAbs) works by transferring antibodies directly into the patient via injection in a muscle. This is defined as a biological product offering rapid protection from a specific infectious disease.

When asked, most parents in China and the US stated that it was important to know if an immunization is active or passive, though it varied whether this information was reassuring or concerning compared with traditional vaccinations. Europeans were comparatively neutral, while fewer Japanese considered it important to know this. In Europe and Japan, parents tended to worry less about the way immunizations work, yet when asked, felt safer with traditional vaccinations.

4. Discussion

Across eight countries, a large sample of New and Experienced parents had limited knowledge about RSV despite the high prevalence of infant RSV infections worldwide [2,14]. The total burden of RSV-related infections in children is substantial. Hospitalization rates are high, and in the UK, for instance, it has been estimated that 20% of children <6 months of age will attend an outpatient healthcare setting with RSV-related LRTI [51,52]. Yet many parents in this study had never heard of RSV or knew only the name. Those who reported being aware of RSV ranked it the second most concerning respiratory disease affecting infants after pneumonia. More respondents reported to be aware of bronchiolitis, yet there is some risk of confusion with bronchitis. Finally, only around half of parents of children diagnosed with bronchiolitis knew the cause behind. Awareness of RSV and bronchiolitis was higher in Experienced than in New parents. This suggests that information about RSV may be needed before childbirth for parents to make an informed decision about RSV immunization in due time before the infant’s first RSV season.

This survey was carried out at a time when the eight countries were variously under lockdown due to the COVID-19 pandemic. It has previously been suggested that media attention to increases in VPD cases and disease severity may increase uptake rates [29]. A large resurgence of RSV cases and hospitalizations of infants was seen in many countries alongside lifting restrictions. The pandemic may have increased public awareness of RSV as well as mAb technology, which may affect attitudes toward RSV immunization.

Overall, parental acceptance of immunizations is related to the perceived risk and severity of the VPD [23–32,50]. In this study, when informed about RSV, most perceived the risk and severity of infant RSV infection to be moderate (61% and 62%, respectively) or high (28% and 33%). Acceptability also relies on perceptions of the immunization itself [28,29,31,53,54]. After receiving information about ‘product X,’ most parents in this study believed it would be moderately or highly beneficial to their infant. While more parents highlighted positive rather than negative aspects of this immunization, responses showed that concerns about safety, efficacy, and durability may vary from one country to another, underlining the need for targeted objective information about RSV as well as mAb immunization in infants. Tailored information efforts might benefit from further examinations of the reasons behind specific local concerns and considerations. When informed, most parents in this study were likely to accept ‘product X’ for their infants if it is included in the childhood immunization program and recommended by the infant’s HCP.

Parental knowledge about mAbs and passive immunization was very sparse. Receiving information about this had a positive or no impact on most respondents. It varied between countries how important this information was and why, again calling for targeted communication. Our study suggests that, overall, parents will likely be less concerned about the mAb technology if ‘product X’ is recommended by HCPs and included in childhood immunization programs. It confirms that HCPs have key impact on parental information levels and acceptance of childhood immunizations [24,26,28,29,31,33]. Still, to many parents, childhood immunization ‘is just something you do,’ it is included in a routine schedule or perceived to be mandatory, which is another well-known driver to vaccination [25,28,31]. Inclusion in immunization programs may act as an endorsement of safety and efficacy [25].

Most parents in our study had given and planned to give their children all immunizations recommended in the schedule of their country or region. Still, 20% had omitted some, mainly due to safety concerns. Beliefs that children receive too many immunizations are known to increase worries about risk of side effects and lead some parents to become selective about which vaccines to accept, delay, or refuse. Several studies have stressed the importance of HCPs presenting parents with balanced and unbiased information about childhood vaccination and VPDs [23,24,26,27,29–38,53]. Given this, most parents are likely to accept additional injections for their children in order to protect their children [55]. Adding a new mAb immunization may require information about the lack of interaction with traditional vaccines if co-administered [56]. New parents found safety information particularly important. Overall, presenting accurate information in simple language during pregnancy and at well-child appointments has been shown to improve childhood vaccination uptake [33].

This study may involve inclusion bias as panel members may be more well-educated, urban dwelling parents with higher employment rates, educational and income levels than average parents. Respondents are considered representative of the online population but carry a risk of self-selection bias. In some cases, e.g. the number of diagnosed RSV cases in Japan, the sample size was relatively low. Also, in electronic surveys, respondents may search the internet for responses, e.g. regarding RSV or mAbs, carrying a risk of overestimation of real-world knowledge. Finally, the study’s exclusion of parents who generally oppose childhood vaccination means the strongest negative views are not represented here. This was, however, a deliberate choice as we aimed to focus on parents who are open to childhood immunization, if hesitant or only partially adherent to current vaccination programs, to examine parental views on RSV immunization, specifically.

While the large cross-national scope is a strength of this study, cross-country comparison also poses challenges. We aimed to ensure similar wordings of the questionnaire in all languages, yet these may have a different impact on respondents in different settings. Also, the stated intentions to immunize may not be followed by actual behavior. Social desirability and courtesy bias may be variously involved depending on the context. Also, it is common to answer with extremes in some countries, while others tend to prefer moderate replies [57]. This paper describes overall tendencies, yet in some cases, there was great country variation. In Europe alone, attitudes toward immunization vary greatly. It is likely that there may also be regional variation within some countries. In addition, parental information levels and attitudes were related to eight very different health-care systems and associated immunization policies. Finally, it should be kept in mind that the overwhelming majority of RSV morbidity and mortality burden occurs in developing countries that are not represented here [2]. While this study was carried out in industrialized countries in which RSV is highly prevalent but relatively few infants die from RSV-related disease, RSV immunization may impact the respiratory disease burden in infants worldwide.

5. Conclusion

RSV causes disease throughout life, but severe infections occur late and early in life, particularly in infants entering their first RSV season. RSV is unpredictable, and all infants may develop severe disease. During the RSV season, most hospitalizations are in otherwise healthy infants born at term and the outpatient burden is high. A new mAb immunization against RSV may prevent RSV-related disease in all infants. Besides meeting an unmet public health need, parental acceptance relies on the perceived burden of RSV and value of immunization. This study shows a great discrepancy between the high prevalence of RSV and the poor parental awareness of it, including the causal relation to infant LRTIs, such as bronchiolitis and pneumonia. This study suggests a need for information to current and future parents about RSV, and when available, about the safety, protection duration, and efficacy of a new infant mAb immunization against RSV. The recommendations from HCP and health authorities are crucial to parental acceptance, and they constitute key information sources, yet national differences in drivers and barriers to childhood immunization call for targeted communication approaches.

Key take-aways

• RSV is highly prevalent and a main cause of infant hospitalizations with respiratory disease

• Parental awareness of RSV is poor – especially in New parents

• 54% of parents whose children had bronchiolitis was told about the cause

• A new investigational mAb immunization for all infants may offer season long protection against RSV with one injection

• When informed about RSV and if the new mAb immunization (product X), most parents were likely to accept this for their infants, if it is included in the childhood immunization program and recommended by the infant’s HCP

• Parents need targeted information about the safety, efficacy, and durability of a new RSV immunization using mAbs

• Information about RSV is needed before childbirth and at early well-child appointments for parents to make an informed decision about RSV immunization before the infant’s first RSV season

Parental attitudes to immunizations are mainly influenced by healthcare professionals and public health authorities

Declaration of interest

GL Mortensen received funding from Sanofi for her contribution to the study, including the methodological design, data analysis, and manuscript writing. GLM received honoraria from Sanofi for participating in an online EU Nirsevimab advisory board, Oct-Nov. 2021. K Harrod-Lui is an employee of Sanofi. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

Reviewer disclosures

Peer reviewers on this manuscript have no relevant financial or other relationships to disclose.

Geolocation information

The study was carried out in China, France, Germany, Italy, Japan, Spain, the UK, and the US (in alphabetical order).

Author contributions

Both authors substantially contributed to the conception, design, analysis, and manuscript reporting of the results of the study.

Acknowledgements

The authors wish to thank all the current and expecting parents who took time to participate. From Research Partnership, who oversaw the data collection and contributed to the survey design, we are indebted to Mark Braund, Beth Clark, Alicia Crawley, and Lauren Craigen. Finally, we wish to thank MD Michelle Roberts, Vaccines Global Medical Lead RSV, Sanofi for sharing her knowledge about RSV and related disease.

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/14760584.2022.2108799

Additional information

Funding

This manuscript was funded by Sanofi.