Literature review

Marketing and business-related COVID-19 literature

Marketing trends have evolved as a natural consequence of consumer behavior changes during the pandemic. Some studies on marketing trends emphasize the effects of COVID-19, which may disrupt marketing strategies and policies (^{Hoekstra & Leeflang, 2020}). ^{Maulana (2020)} does an in-tegrative literature review focusing on research trends in marketing science before the COVID-19 outbreak. This author proposes a research agenda highlighting social media and social and cause-related marketing studies concerning the pandemic.

On the one hand, supply chain disruption in the pandemic era is a key issue explored by diverse authors (^{Sarkis, 2021}). Different industries were and continue to be affected by this problem, particularly the food industry, as evidenced by the different studies on such matters (^{Hobbs, 2020}). On the other hand, the increase in online activities and digitalization is an important research topic with relevant implications for individuals and industries. A large number of studies find that e-commerce has grown and will continue to do so, thanks to the increase in global online activity and home office approaches. As a result, we find a large number of studies addressing the challenges of the online channel (^{Jílková & Králová, 2021}).

Tourism is an industry that has been particularly impacted by the initial confinement and the continuous regulations and fears that prevent people from traveling -studies such as ^{Shin and Kang (2020)} stress technology's usefulness in facing such challenges. An important change related to technology is the study of how people search for information (^{Bento et al, 2020}). This is an essential feature of consumer behavior relevant to governments and businesses. ^{Paakkari and Okan (2020)} emphasize how health literacy is an underestimated problem. For companies, business intelligence data that helps to understand search patterns and trends is vital in the current changing environment.

Moreover, we need to consider the amount of time people spend online derived from the COVID-19 pandemic. This is known as the "attention economy," a recent but well-researched topic in 2020. Whether consumers look for information and make decisions following influencers or have other strategies is a topic that has also attracted researchers' attention.

Therefore, in a world of literature, this study aims to answer the following research question: Which are the salient topics addressed in the consumer behavior literature during the pandemic, and how have they changed?

The use of surveys among researchers is common (^{Di Crosta et al., 2021}; ^{Eger et al., 2021}; ^{Gu et al., 2021}; ^{Jílková & Králová, 2021}; ^{Mehta et al., 2020}; ^{Satish et al., 2021}). Others have used secondary data, such as the work of ^{Hoekstra and Leeflang (2020)} and ^{Zwanka and Buff (2021)}. The number of citations can measure the impact of research. Table 1 summarizes the most cited articles related to consumer behavior and COVID-19. By looking at the information in this table, it is visible that secondary data and surveys are still the most common data collection methods, only one study conducts an experiment, and few works adopt online panel data.

Lockdown due to coronavirus impacts people's interaction (topic 1)

Lockdown due to COVID-19 has caused several changes in consumer behavior, which has created variations in spending patterns and fluctuations in prices of various products, which may continue to change since it is not known when the pandemic will end (^{Borsellino et al., 2020}). In times of crisis, it is necessary to consider those factors that serve to model consumer behavior, such as the attitude towards risk, which reflects how the consumer reacts to risk, and the perception of risk, when consumers consider how much they are exposed (^{Mehta et al., 2020}). The lockdown, as well as social distancing recommendations that were implemented to fight COVID-19, generated significant changes in consumer behavior. For example, the limits between professional and personal life are practically non-existent since many people work, study, and relax at home (^{Sheth, 2020}); hence, consumers look for simple products and services that are perceived as of great value by simplifying their lives (^{Mehta et al., 2020}).

COVID-19 has generated changes in consumers' priorities due to the mandatory isolation adopted as a preventive action, reducing the consumption of unnecessary items and increasing the consumption of groceries and home entertainment (^{Mehta et al., 2020}). In this context, many restaurants stopped working. Hence, consumers had to eat more at home, which increased the traffic of websites related to cooking recipes, implying a change in consumer preferences (^{Borsellino et al., 2020}). In addition, the purchase of prepared foods decreased since they are perceived as less healthy and because people have more time to prepare their own food; on the contrary, more fresh vegetables are being bought, as they are considered healthier foods (^{Laguna et al., 2020}). However, even though consumers bought fruit instead of beer at the beginning of the pandemic, after a while, they went back to buying beer and snacks because they were forced to stay home to prevent infections (^{Anastasiadou et al., 2020}).

Panic buying behavior is a reaction to situations of fear and uncertainty, which generates an accumulation of basic (rational) goods or unnecessary (irrational) goods and, consequently, a shortage in the supply chain (^{Borsellino et al., 2020}). The fear of getting sick, as well as the difficulty in accessing several products, have been the main factors that cause hoarding behavior (^{Hao et al., 2020}). Other factors that influence the hoarding of products in times of crisis are education, income level, purchases in online stores, gender, and profession in fields related to medicine (^{Wang & Hao, 2020}). On the one hand, hoarding is a common reaction when there is uncertainty about the future supply of products that cover basic needs. On the other hand, an informal market may arise where unauthorized intermediaries hoard essential products and generate price increases, or even counterfeit products may be sold (^{Sheth, 2020}). ^{Anastasiadou et al. (2020)} found that consumers are more likely to accumulate a certain product if its price or maintenance cost is low or if there is a risk of receiving the product due to a crisis.

At the beginning of the pandemic, when a consumer made a purchase, he or she tried to be as fast as possible, allocating significant importance to the disinfection and cleaning of bags and shopping carts, as well as preferring to buy locally produced products, perhaps to avoid contamination by reducing their manipulation (^{Anastasiadou et al., 2020}). In this sense, the general preference for shopping, especially in Latin America and other developing regions, has shifted from traditional points of sale to more modern channels, such as supermarkets or hypermarkets, due to a perception of cleanliness and safety (^{Borsellino et al., 2020}). This is confirmed by another study that argues that those who prefer modern commerce based their decision on attributes of safety, cleanliness, and vehicle parking (^{Bohorquez-Lopez et al., 2022}).

Increase protection to maintain operations (topic 2)

Previous research found that fear is one of the main determinants of consumer purchasing behavior in crises (^{Eger et al., 2021}; ^{Hassan & Soliman, 2021}; ^{Rather, 2021}). These studies also indicated that people tend to comply with expectations and restrictions in risky circumstances. ^{Roberts and David (2021)} identified that fear of COVID-19 can cause increased self-efficacy as well as perceived behavioral control, with the emotional response influencing self-protective behavior (^{Liu et al, 2021}). During the COVID-19 pandemic, the perceived threat is positively correlated with the global adoption of preventive measures, resulting in elevated self-protection against the imminent threat (^{Itani & Hollebeek, 2021}). In this context, these authors found that fear causes many people to comply with social distancing since the severity of the threat is relatively high, so social distancing is perceived as an effective coping mechanism by those who believe that they are more likely to contagion.

^{Czarniecka-Skubina et al. (2021)} studied the catering industry, which has adopted new practices to minimize the risk of COVID-19 contagion, identifying the main protection measures such as hand disinfection, table disinfection, use of masks and visors by staff, the possibility of cashless payments, and maintenance of social distance. Within the protection measures that take into account a comprehensive approach to reduce the transmission of COVID-19 both inside and outside the facilities, that is, not only focusing on consumers but also on the staff working in organizations, we can highlight: vaccination of employees, ensuring that social distancing is practiced, ensuring that masks are used appropriately, periodically evaluating employees for COVID-19, promoting frequent hand washing, cleaning surfaces exposed to different people, and ensure adequate ventilation (^{Trmičič et al, 2021}).

^{Liu et al. (2021)} suggested that protective motivation theory (PMT) is often used when an individual's self-protective behaviors arise through fear, such as the fear many people have experienced contracting COVID-19. In the context of the pandemic we are experiencing, PMT can help understand how consumers perceive threats and how their reaction, when faced with them, impacts their behavior. PMT has been used to predict behaviors related to health protection when it is subjected to several threats (^{Min et al., 2021}), as well as to show that the perceived threat and the effectiveness of the response could contribute to fear, which is a predictor of consumer behavior during the COVID-19 pandemic (^{Kim et al, 2021}).

Other studies have used PMT to explain that people's fear influences their behavioral responses in such a way that they can minimize the resulting trauma, which explains why many people engage in risk-reducing behaviors through self-protection in the face of COVID-19 to reduce the possibility of infection (^{Liu et al., 2021}). In this sense, behaviors that minimize risks (e.g., wearing masks, maintaining social distance, washing hands regularly) are present in people who fear the consequences of COVID-19 (^{Adunlin et al, 2021}). In other words, PMT helps to understand people's cognitive process when evaluating a threat, considering their ability to deal with it, resulting in possible protective actions. Therefore, given the current pandemic, consumers' perceived threats and coping evaluations may influence the protective actions they take, for example, when visiting a restaurant or engaging in activities with others (^{Min et al, 2021}).

Sustainability of consumption and current business models (topic 3)

Many consumers have been financially affected by the pandemic, so their long-term purchasing behavior has become more frugal; that is, consumers buy what they really need instead of making unnecessary purchases. Hence, one of the consequences of the pandemic has been the shift toward more responsible purchasing behavior, due not only to limited resources but also focused on sustain-ability (^{Mehta et al., 2020}). In other words, consumers with sustainable consumption behavior tend to have a deeper holistic outlook and concern about moderation in consumption (^{Phang et al, 2021}). ^{Radcliffe et al. (2021)} pointed out that the sustainability of face-to-face food systems and markets has been widely discussed and criticized in the literature, especially from the point of view of resilience. These authors highlighted the potential of bringing these spaces online to contribute to sustainability in the face of system shocks such as during the COVID-19 pandemic. ^{Ha et al. (2021)} found that consumers who were resilient during the pandemic, that is, were able to recover quickly after a crisis, were more likely to patronize small businesses, thus contributing to their survival.

The pandemic brought as a consequence a change in the priorities of consumers, generating new purchasing behaviors to cope with the uncertainty of the pandemic, demonstrating greater concern for the social and ecological, and supporting efforts to achieve sustainability and well-being of the society in this new economic environment (^{Sharma et al, 2021}). As COVID-19 spread throughout the world, consumers faced major changes in their daily activities, including the closure of many businesses that did not know how to adapt, while those that did experience supply chain disruptions were influenced by product availability (^{Ha et al, 2021}). In this context, people spent much more time in their homes, so they had to adopt different technologies to make purchases, and they were much more aware of the importance of saving water and energy, which has generated greater awareness of waste, as well as the adoption of some pro-environmental and social practices (^{Arias et al., 2021}). ^{Phang et al. (2021)} stated that individuals with sustainable consumption behavior could alter their behaviors to favor mindful consumption, adopting less panic and compulsive buying relative to those who do not.

Focusing on the economic impact of the COVID-19 pandemic, most companies, regardless of their size or sector, have been forced to rethink their strategies, especially concerning their operations related to stakeholders (^{Vãtãmãnescu et al., 2021}). In this context, it is more important than ever for small businesses to be able to understand the behavior of their customers so that they can maintain themselves and be profitable (^{Arias et al, 2021}). These authors identified that small companies are especially vulnerable in times of crisis due to a lack of resources compared to large companies. Therefore, small businesses must analyze how, when, where, and to whom they sell their products to achieve long-awaited sustainability during and after the crisis (^{Ha et al, 2021}). In this sense, small businesses could benefit from a better understanding of their consumers, such as knowing their emotions related to the pandemic (resilience, optimism, etc.) and their profile (generational category, employment situation, income, etc.). By segmenting their customers, they will have more and better tools to give them what they need with limited resources (^{Ha et al, 2021}).

COVID-19 has significantly impacted small businesses, many of which remain at risk of disrupting operations. However, now more than ever, it is vital to understand the factors that contribute to the survival of small businesses in the face of a crisis, such as the frequency of purchase by their consumers and the number of services used and preferred, which can serve to achieve their survival during this difficult time (^{Ha et al, 2021}). ^{Vătămănescu et al. (2021)} empirically validated the importance of product sustainability attributes, highlighting that social and environmental sustainability practices are necessary for good business performance, especially during the pandemic. In addition, small businesses must build trust with their consumers to foster long-term, mutually beneficial relationships; they can achieve this by posting relevant information on their social networks to generate a feeling of identification among their followers (^{Ha et al, 2021}). In that sense, online communities can be considered helpful for building a community around shared ethics and beliefs that can support the greater use of sustainable consumption practices (^{Radcliffe et al, 2021}).

The pandemic moves online consumption (topic 4)

^{Pham et al. (2020)} analyzed the role of COVID-19 as a moderating variable between the consumer's perception of interest and their online shopping activities, finding that this situation encourages consumers to make purchases using digital channels, significantly reducing the number of purchases and visits to physical stores due to fear of contagion. Instead, they shopped online much more than before due in part to restrictions on movement, which may hold when things return to normal due to convenience (^{Borsellino et al., 2020}). These authors identified that the increase in online purchases had affected food deliveries since, in some cases, they were not only delayed but not even shipped. On the consumer side, it is increasingly necessary for them to have information to control, prevent, or respond to fear and perceived risks, which generates a high level of interactivity and social presence in electronic commerce platforms (^{Addo et al., 2020}). This will enable them to adopt new attitudes, such as shopping on different websites, changing stores when shopping, eating at nearby restaurants and using store pickup (^{Anastasiadou et al, 2020}).

The COVID-19 pandemic has accelerated digital transformation, with digital channels becoming more important than ever. In contrast, the lockdown has made companies aware of the importance of digitalization throughout the value chain to improve not only resilience and efficiency but also demand forecasting (^{Vătămănescu et al, 2021}).

The need to face the pandemic crisis has forced small companies and intermediaries to embrace vertical integration and omnichannel strategies (^{Gutiérrez-Leefmans, 2022}). This crisis period has prompted a change in consumer behavior that has migrated from physical stores to online purchases, which is likely to continue in the future, increasing the frequency of online purchases and changing their consumption habits (^{Yin et al, 2021}). Along the same lines, ^{Mehta et al. (2020)} indicated that these changes in behavior result in a change in the spending pattern, as well as the use of various electronic contact points to buy, such as the official product site, social networks, mobile platforms, etc. This impacted the reduction of traditional outdoor advertising and decreased visits to shopping centers due to social distancing. The challenge for companies now is developing an effective omnichannel strategy where the marketing mix is consistent across channels.

^{Yin et al. (2021)} argued that previous studies found that changes in consumer behavior due to COVID-19 have created many opportunities for industry reform, which should be used to integrate offline processes with online processes since, in this way, economic development will be promoted (^{Yin et al, 2021}). ^{Akram et al. (2021)} point out that online consumption and digitization in a crisis context not only impact customers' well-being but also imply great challenges and development opportunities for the retail industry. Therefore, the evolution of online markets can make it possible for customers to connect with local suppliers, fostering the creation of a community around ethical and responsible consumption. In this sense, online markets can help efficiently connect customers and suppliers to reduce physical contact and interactions in public spaces, potentially fostering a real community based on caring, shared interest, and consumption ethics (^{Radcliffe et al, 2021}).

In the new normal, digital technologies play a fundamental role in maintaining retail operations and in the possibility of offering quality and uninterrupted customer service; these technologies help retailers improve their crisis management capabilities, which benefits the entire value chain (^{Jiang & Stylos, 2021}). It is important to remark that those companies with capabilities based on digital technologies can optimize their businesses with much more flexibility in response to changes that arise in the external environment (^{Wang et al., 2020}). This avoids crowding in their premises and the consequent spread of contagion by offering free store pick-up or home delivery to clients (^{Borsellino et al., 2020}), and strategically improves their online presence and attracting consumers with offers specific to their profile, thus mitigating the decrease in sales (^{Koch et al., 2020}).

Research agenda

We propose the following research agenda derived from our analysis and confirming previous studies in the literature. In contrast to previous studies, we find that future research areas go beyond technology and information search (^{Cruz-Cárdenas et al, 2021}) or social and cause-related marketing (^{Maulana, 2020}). It is important to highlight a particular emphasis needed in studies related to small companies' business models and digital transformation. Various core marketing areas need researchers' attention in the context of COVID-19, such as:

Two important future research areas related to consumer behavior are the study of augmented reality (AR) and neuromarketing, where few studies can be found. Relating the pandemic's effects on consumers' emotions and desires to an immersive reality where users can feel safe and have a unique experience can certainly bring interesting insights.

Among our findings' practical and managerial implications are the focus needed on marketing for local consumption. In omnichannel strategies, a special emphasis is needed on customer service, which literature related to COVID-19 has also highlighted. Not only is digitalization required but understanding customer value shifts seems to be vital for successful business models. Also, innovative ways to enhance the digital experience should be explored, such as AR, where technology will play a vital role for companies.

Regarding policy implications, security and consumer protection are still issues businesses face. Hence, the need for proper regulations that help them continue operations, ensuring consumer safety. Other issues concerning government regulations are the need for sustainable business models and digital transformation. In some countries, SMES receive financial help from governments to survive and invest. However, that is not a common trend in developing countries, where SMES represent an important part of employment.