1. Introduction

Social media has developed into one of the key digital marketing platforms, and influencer marketing has emerged as a rising star in this space, with social media influencers playing crucial roles. According to Po-Yen Lee et al., "influencers" are people or organizations who have amassed a certain audience through social media platforms and have a direct impact on consumers' purchase decisions [1]. These people gain a significant following, establish a fan base, and start offering advice to their followers, becoming social media influencers (SMI) [2]. Today, everyone can start influencing people. Anyone who creates an audience on social media can use this technique to sway that audience [3].

Influencer marketing pushes brand communication through social media to a wider consumer base [4][5]. Influencer marketing is becoming one of the most effective strategic marketing options because to the rapid expansion of social media [1]. Specifically, Demetris Vrontis et al. argue that many brands are becoming aware of the benefits of working with SMIS [2]. Influencer marketing, for instance, involves companies supporting and promoting their goods and services by giving away free merchandise or charging consumers (IM). According to research, approximately 60% of brands use IM to meet their social network communication objectives [6].

Not surprisingly, the number of studies on social media influencer marketing has exploded in recent years and has been conducted in various fields [2]. However, in the hospitality field (including travel, tourism, hotels, and restaurants.), influencer marketing has been less studied by scholars and is fragmented and scattered. More importantly, mass travel restrictions caused by the continued spread of the new crown epidemic have wreaked havoc on hospitality [7]. Hospitality has "faced collapse" and is "fighting for survival" [8]. The current crisis, though, is also seen as a critical juncture for the industry [9]. It affects all hospitality elements, including marketing practices [10]. Therefore, the study of SMI in hospitality is critical.

This study summarizes the existing literature, outlines the current research directions of SMI, and proposes relevant research gaps. It provides more possibilities for future scholars' research and proposes new development strategies for the hospitality industry in the post-epidemic era.

2. Research Selection

Since Scopus is the world's largest database of abstracts and citations for peer-reviewed research literature, the author first decided to search there for pertinent literature [11]. In addition, this study restricted the search to peer-reviewed journal articles written in English, omitting other non-reference publications such as books [2]. This is so because peer-reviewed journal publications are thought to be the most influential and represent confirmed information [12]. Then enter the core words in the "Keywords, Abstracts, and Titles" column, and use the search algorithm to search. Start with "influencer*" or "influencer marketing*" or "social media influence*" or "SMI" as the first series of keywords. Make "hospitality*" "travel*" "restaurant*" "hotel*" or "tourism" the second set of keywords. Finally, the cross-merge search of the keywords from these two parts is carried out to expand the scope of the search articles continuously, and 35 articles are found by searching for different matching keywords. 21 articles connected to SMI in hospitality were finally vetted after the general substance of these articles was read. The author then studied each paper's whole text in order to gather data relevant to the article's subject.

3. Results and Analysis of Current Research

First of all, for the publication year, the publication range of these articles is from 2017 to 2022. This is in line with the arguments in the SMI systematic review literature by Demetris Vrontis et al. [2]. They argue that research on SMI started to proliferate in 2017. It shows that scholars in the field of hospitality are increasingly interested in influencer marketing. In addition, the research methods of this literature are mostly quantitative empirical analysis or a combination of qualitative and quantitative, and there is no retrospective research literature.

The author classified the thematic directions of the 21 articles, combined them with the research themes of SMI summarized by [2], and finally divided them into four main research directions. In addition, some literature content topics will overlap so that they will be mentioned multiple times. Through a systematic literature review of research directions, this study sorts out the current research directions for researchers and promotes future scholars' research on SMI in hospitality.

4. Effectiveness and Impact of IM

First, scholars' research on SMI in hospitality mainly focuses on the impact of SMI on people's behavioral willingness and travel decisions. With different subjects as the research background, Chatzigeorgiou, C. argues that SMI influences millennials' decision-making when choosing rural tourist areas as potential destinations [3]. Payal S. Kapoor et al. use eco-friendly hotels as their research topic, and they discover that these establishments are increasingly relying on SMI to influence guests' decisions to travel sustainably [13]. Ong &Ito took Hokkaido as a case study and believed that SMI could effectively change consumers' attitudes, especially the destination image, thereby affecting consumers' travel intentions and word-of-mouth willingness [14]. Lara Madureira and Bráulio Alturas took the country as their background and discussed the impact of SMI on Portugal's tourism and travel industry in the context of the epidemic [15]. The study by Martnez-Sala et al., which involved a survey of DMOs and an examination of the influencers' networks in the Spanish tourist industry, attests to the validity of these SMIs and the incredible potential they present for destination marketing [16].

Moreover, X.Y. Leung et al. put SMI into Saudi culture from a gender perspective, arguing that the credibility of male influencers and the social attractiveness of female influencers lead to a higher willingness to visit restaurants [17]. Xu Xu and Stephen Pratt proposed that SMI endorser–consumer congruence or endorser–destination congruence would actively promote tourists' willingness to travel through self-congruity theory [18]. Rebeka-Anna Pop et al. included mediator variables in their analysis, highlighting how consumers' faith in influencers might boost their desire to travel [19]. Findings suggest that influencers contribute to increased destination visit intent [20].

Therefore, a hospitality influencer's primary responsibility is to improve visit intent, change how people see the place, create content, foster online engagement, raise brand awareness, and draw more customers to a certain hotel, eatery, or tourist destination [18][21].

In addition, scholars have assessed the impact of sponsorship disclosure on consumer responses in social media influencer marketing. Kapoor, P.S. analyzed how sponsorship status affects the quality of information argumentation through an article in an environmentally friendly hotel case study [22]. In order to raise tourists' awareness and urge them to choose the hotel, they think SMI should provide sponsored messaging that offers logical and impartial information about the hotel's sustainable operations. Another article by Po-Yen Lee et al. provides insights into how businesses and SMIS should design appropriate sponsorship collaborations to meet consumer needs [1]. Although this part of the article in the hospitality field has been mentioned, the content needs to be more, and the research gap is significant.

4.1. Content Attributes of SMI

On the other hand, the features and reliability of influencer content and the subsequent results are scholars' most important and prominent research themes. Andrzej Szymkowiak et al. proved through experiments in their research that the content published by SMI has an impact on the evaluation and selection stages of tourism-related services, and the internal attributes of the content can significantly affect travelers' choices [23]. Similar results were reached by Cátia Guerreiro et al., who said that SMI followers frequently appreciate their information, go to the locations they recommend, and let them guide their decisions [24]. From a DMO perspective, Yi Xuan Ong & Naoya Ito argue that DMOs should explore using SMI to create interactive and engaging content to attract consumers' attention and enhance consumers' experience of activities [14]. Similarly, Femenia-Serra & Gretzel also explored the range and structure of tourism SMI marketing campaigns in the DMO study [25]. On this basis, Femenia-Serra et al. from the perspective of COVID-19, argue that the epidemic is changing SMI and their content and communication practices [10].

In addition, the main focus of many scholars' discussions is the importance of reliability in the IM environment. For example, Rebeka-Anna Pop et al. argue that SMI can build trust in its content, then SMI significantly impacts all stages of the travel planning process [19]. Moreover, companies should pay attention to the credibility of SMI information sources. Po-Yen Lee et al. also mentioned in the text that owners and influencers should increase the credibility of sources and information while cooperating for a win-win situation [1]. Travelers may believe sponsored attribute-value messages more than sponsored plain suggestion messages, according to Payal S. Kapoor et alresearch .'s on argument quality, a crucial aspect in trustworthiness ratings [22]. Chatzigeorgiou studied their trust evaluation of IM from the perspective of millennials. He argues that millennials evaluate an influencer's credibility mostly based on the influencer's fan base, personality as displayed in posts and comments on social media, and activity as shown in posts, videos, and images [3]. As a result, customers consider SMI to be more credible, trustworthy, and similar, and they view it to have a stronger social presence. These factors have an impact on consumers' purchase decisions and attitudes toward SMI-endorsed products [26].

To sum up, scholars mainly focus on the impact of SMI on consumers and the research on the intrinsic level of SMI, but there are still many research gaps in other directions. Researchers are still developing their understanding of SMI in the hotel sector. Therefore, future scholars should comprehensively understand the mechanism of SMI from all aspects and explore more possibilities in the hospitality field.

5. Recommendation

This paper reviews and summarizes the existing research and finds that the current research directions of scholars mainly focus on four levels: impact mechanism, content quality, credibility, and sponsorship status. However, there are still many research directions that have not yet been explored, such as the impact of SMI on consumer behavior, exploring the perception of SMI in hospitality from the perspective of consumer psychology, the role of SMI as a strategic plan for hospitality, and the impact of SMI on consumer outcomes under different sponsorship states. In addition, this paper also puts forward some proposals for the application of SMI in the hospitality industry from a practical point of view.

During the epidemic, the development of SMI provides new development opportunities for hospitality. Because distance has become an obstacle under the influence of the epidemic, people have fewer and fewer opportunities to choose travel, and they choose travel destinations more carefully. On the other hand, professionals feel that influencer marketing is more efficient and affordable than traditional media [10]. Therefore, many restaurants, hotels, and tourist destinations can cooperate with SMI while reducing costs and using SMI's influence to stimulate consumers' travel intentions.

Enterprise managers should cooperate reasonably with influencers on various social platforms. Consider TikTok, a platform for short videos. In the post-pandemic age, TikTok is the media platform that is expanding the fastest, and it was the most downloaded app worldwide in 2020 and 2021 [27]. TikTok will be used for influencer marketing by 42% of US marketers on this platform in 2021 [28]. Managers in the Hospitality space can promote their products here. For example, suppose a newly established hotel wants to market itself. In that case, it can reach cooperation through SMIs with similar positioning on the TikTok platform, invite them to stay in the experience, and share it through their accounts with many followers, which can quickly increase the hotel's exposure.

In addition, live broadcast is also a good media channel. Many Internet celebrities sell goods, promote products, and gain income through live broadcasts. This model is also an e-commerce model. There are also many travel products appearing in the live broadcast rooms of various influencers, such as accommodation packages, restaurant packages, tourist attraction packages, etc. Through the influencer's live broadcast room, consumers can watch food tastings and the introduction of attractions. In this method, influencer engagement is established, and superior interactive and consuming process experiences are obtained. Additionally, it fulfills people's inner perceptual demands, which has the impact of causing word of mouth to spread quickly [29].

6. Recommendation

This paper reviews and summarizes the existing research and finds that the current research directions of scholars mainly focus on four levels: impact mechanism, content quality, credibility, and sponsorship status. However, there are still many research directions that have not yet been explored, such as the impact of SMI on consumer behavior, exploring the perception of SMI in hospitality from the perspective of consumer psychology, the role of SMI as a strategic plan for hospitality, and the impact of SMI on consumer outcomes under different sponsorship states. In addition, this paper also puts forward some proposals for the application of SMI in the hospitality industry from a practical point of view.

During the epidemic, the development of SMI provides new development opportunities for hospitality. Because distance has become an obstacle under the influence of the epidemic, people have fewer and fewer opportunities to choose travel, and they choose travel destinations more carefully. On the other hand, professionals feel that influencer marketing is more efficient and affordable than traditional media [10]. Therefore, many restaurants, hotels, and tourist destinations can cooperate with SMI while reducing costs and using SMI's influence to stimulate consumers' travel intentions.

Enterprise managers should cooperate reasonably with influencers on various social platforms. Consider TikTok, a platform for short videos. In the post-pandemic age, TikTok is the media platform that is expanding the fastest, and it was the most downloaded app worldwide in 2020 and 2021 [27]. TikTok will be used for influencer marketing by 42% of US marketers on this platform in 2021 [28]. Managers in the Hospitality space can promote their products here. For example, suppose a newly established hotel wants to market itself. In that case, it can reach cooperation through SMIs with similar positioning on the TikTok platform, invite them to stay in the experience, and share it through their accounts with many followers, which can quickly increase the hotel's exposure.

In addition, live broadcast is also a good media channel. Many Internet celebrities sell goods, promote products, and gain income through live broadcasts. This model is also an e-commerce model. There are also many travel products appearing in the live broadcast rooms of various influencers, such as accommodation packages, restaurant packages, tourist attraction packages, etc. Through the influencer's live broadcast room, consumers can watch food tastings and the introduction of attractions. In this method, influencer engagement is established, and superior interactive and consuming process experiences are obtained. Additionally, it fulfills people's inner perceptual demands, which has the impact of causing word of mouth to spread quickly [29].

7. Conclusion

This paper mainly determines the focus of current scholars' discussions, the existing research gaps, and future development directions through a literature review. It aims to provide new ideas for Hospitality enterprise managers to use SMI development in the post-epidemic era better. This paper only conducts relevant searches on the "scholar" search tool, excludes books, conference proceedings, etc., and only keeps journal articles. Furthermore, although the range of relevant search terms used in the literature review was carefully selected, these terms may not have been included in the recent emergence of new terms in the rapidly evolving social media and marketing field. For example, an influencer may also be a "vlogger" or "blogger," or "influencer endorsement" may also be some specific name. In the future, scholars can expand the scope of the article for further study.