According to WHO, until 3 August 2022, the confirmed cases of coronavirus disease 2019 (COVID-19) were about 580 million, including 6 401 046 deaths .
Outbreaks and clusters of SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) infections in a variety of occupational settings have been reported since the start of the pandemic, particularly in sectors where workers operate in physical proximity to others (such as co-workers, patients, customers and public), within indoor settings or with shared transport or accommodation. The majority of occupational COVID-19 clusters reported were, of course, from the health sector, where testing of healthcare workers (HCWs), the ‘hard core’ of pandemics since the beginning, was a priority. The health and safety of these workers certainly continues to be a public health priority. Moreover, many clusters were also reported in various factories, in manufacturing and office settings .
COVID-19 still poses a significant challenge for occupational health and safety (OHS). As the pandemic is still ongoing, job organization is changing and the health effects of COVID-19 will very likely have short, mid-term and long-term consequences, with differences between younger and older workers as well as with individuals with preexisting medical conditions as compared with healthy ones, a life course perspective must be considered to understand the changing nature of work and health throughout the pandemic [3▪].
Since the beginning of the pandemic, the reduction of the strict containment measures has appeared both as a challenge and an opportunity for OHS. To date, the critical issues related to the impact of the pandemic on public and occupational health were higher during the first and second pandemic waves in 2020, despite the containment measures adopted (e.g. mask-wearing, social distancing, lock-downs, teleworking, mass testing strategies and vaccination); such issues are still present and mainly concern the recurrence of the waves themselves, the rapid mutability of the virus with the continuous discovery and spread of variants, the risk perception, the vaccination coverage and hesitancy, as well as the social and economic need to return to everyday life.
From a scientific research point of view, an exciting and also somehow surprising aspect was that the pandemic inspired feverish scientific activity, covering several topics. To understand the scale of this phenomenon, let us consider that a preliminary search in Medline entering the acronyms 'SARS-CoV-2’ or ’COVID-19’ yields more than 200 000 results in the years 2020–2022 alone, as opposed to the just over 500 000 studies surveyed by the same search engine under the terms ’HIV-infection’ or ’AIDS’ over the last 40 years.
As largely expected, most of the available scientific literature focused on HCWs; also, notably, this research effort was possible through the collaboration among different research centres across various countries, and through the investigation of multiple fields (mainly mental health outcomes) (Fig. 1).
This shared approach enabled the creation of cohorts reaching even tens of thousands of workers, across various countries and continents, such as the ORCHESTRA Cohort [4,5▪], AZ HEROES study [6▪] or other large cohorts from general population including workers [7,8▪▪].
Despite this outbreak of scientific research, some aspects of OHS deserve further investigation, possibly with a high-quality methodological approach and field-based.
This review aims to rapidly explore the scientific evidence published in 2021 and 2022 concerning the impact and management of COVID-19 on the working population, with special attention to clinical outcomes, vulnerable workers’ evaluation and SARS-CoV-2 vaccines’ effectiveness in relation to viral variants’ diffusion, breakthrough infections and reinfections, also in order to identify possible future research areas on specific topics of interest.
Due to the large number of studies published and their predictable lack of homogeneity in terms of quality, we carried out a rapid review to summarize the evidence relating to work and pandemics. In this selective review, we did not apply a systematic approach but rather used a targeted Medline and Cochrane Database of Systematic Reviews search strategy related to ‘SARS-CoV-2’ and ‘COVID-19’ topics, from an OHS perspective, complemented with a thorough search of references in key publications. For the same reason, the data used in this study derive both from primary and secondary research (reviews), published in the English language from 1 January 2021 to 30 June 2022.
Two reviewers (M.G.L.M. and G.S.) screened the studies independently, and differences were resolved by discussion; and a third reviewer (S.P.) was involved if an agreement was not reached. The main results were grouped according to two points of view on SARS-CoV-2 pandemic issues: clinical outcomes (and vulnerable workers) and SARS-CoV-2 vaccine effectiveness, across two occupational setting groups (healthcare and nonhealthcare) with narrative synthesis and then discussed at the same time. The selection process was done using some freeware [9,10]. In addition, a knowledge map was constructed using VOSviewer version 1.6.18, a software tool for building  to calculate a co-occurring relationship among keywords (co-word analysis), as reported in the Introduction section.
CORONAVIRUS DISEASE 2019, CLINICAL OUTCOMES AND VULNERABLE WORKERS
It is estimated that before the SARS-CoV-2 pandemic, about 800 million people of working age were living with disabilities worldwide. The SARS-CoV-2 pandemic poses new challenges for occupational health by creating two poles of interest, consisting of returning to work after health problems and resuming work during a pandemic, with special consideration for workers with vulnerabilities, including those acquired as a result of the pandemic itself [12–14]. Workers can be considered vulnerable on both the occupational (e.g. HCWs, essential services employees and temporary workers) and clinical (immunocompromised or disabled workers, pregnant women, elderly and ’post-COVID-19 condition’) or socioeconomic levels (such as income, race and ethnicity).
Even if the pandemic exacerbated existing inequalities among vulnerable groups, such as migrant workers, there was an exponential increase in studies related to the pandemic. However, there is still a limited number of original publications associated with the impact of COVID-19 on the health of occupational migrants . As reported by Cote et al., several studies focussed on how the pandemic affects migrant workers, including care workers and seasonal farm workers . Moreover, in times of health crisis, workers with precarious status, who are often (im)migrants, members of ethnic minority groups and women, found themselves on the front line of providing and maintaining essential services, at the risk of their own health as well as that of their relatives and other colleagues, when the conditions for preventing transmission and controlling the disease are not adequate.
In this context, occupational physicians must embrace the challenge of protecting the health of migrant workers, considering that issues and gaps are still present in the occupational health and safety systems, such as the lack of quality standards, poor information and health education, limited risk assessment, poor or inadequate health surveillance and case management. Moreover, there is a lack of analysis of the connections with working conditions, and it is occupational physicians who should be the primary link between workplace needs and migrant health protection . The role of occupational physicians can also be remarkable in defining fitness for work for the postpandemic era, providing useful insights for an integrated approach, for example, in the management of return to work as well as supporting equal access to safety measures and vaccination/immunization programs in the workplace. At the same time, occupational physicians should consider that if migrant workers are in people-contact occupations, they may need to be given high priority in these programs .
Concerning clinical outcomes, a vast and rapidly growing literature has examined the impact of the pandemic on mental health in the shorter and longer terms [18▪▪,19,20▪,21▪,22,23]. Fan et al. found that a significant proportion focused on either mental illness and well being outcomes, such as anxiety and posttraumatic stress, depression and stigmatization, as well as outcomes related to the risk of infection by COVID-19 [18▪▪]. A further issue related to pandemics is the stigmatization of occupations with contact with COVID-19 or suspected patients. Schubert et al. found clear evidence of the psychological consequences of COVID-19-related stigmatization for depression and anxiety disorders. Although this was most evident in the early stages of the pandemic, to date, it has not completely disappeared, and to promote workers’ health, antistigma strategies should also be implemented in the workplaces . Sleep disorders [25–27], burnout , anxiety and depression  and suicidal behaviour are the most documented problems among workers during the COVID-19 pandemic, first and foremost among HCWs.
The direct and – perhaps more importantly – indirect consequences of SARS-CoV-2 infection on the psychological health of workers constitute (mainly because of the medium-to-long-term effects) priority aspects to be taken into consideration, not only when choosing containment measures but also for the enhancement of care and support services for those adversely affected by this health earthquake, first and foremost the HCWs again. Intervention programs aimed at supporting psychological issues resulting from the pandemic are as urgent as they are challenging to implement. Although several groups around the world are working to develop initiatives to support the well being of HCWs coping with the psychological impact of the COVID-19 pandemic through easily accessible psychological support services [30–32], still evidence lacks on the effectiveness of randomized trials that can provide orientation on which treatments may be beneficial for the mental health of frontline HCWs facing the current pandemic .
In this regard, we report that an interdisciplinary research group at the University of Verona, Italy, started a parallel-group randomized controlled trial to assess the feasibility, acceptability and efficacy of a mindfulness and compassion-focused programme on frontline nurses who had been working during the COVID-19 pandemic. The research aims to present a scientifically validated intervention for those healthcare professionals most exposed to the stressful conditions of working during the COVID-19 pandemic, trying to fill a gap in the current scientific literature (L. Bodini, C. Bonetto, S. Cheli et al., unpublished observation).
A new challenge for OHS management is the ’Post-COVID-19 condition’ (previously referred to as ’long COVID’), a ‘postviral’ condition that occurs in individuals with a history of probable or confirmed SARS CoV-2 infection, usually 3 months from the onset of COVID-19 with symptoms that last for at least 2 months and cannot be explained by an alternative diagnosis. Common symptoms include fatigue, shortness of breath, cognitive dysfunction, and others and generally impact everyday functioning. Symptoms may be of new onset following initial recovery from an acute COVID-19 episode or persist from the initial illness. Symptoms may also fluctuate or relapse over time . The most frequently reported symptoms, not restricted to severe acute disease, are profound fatigue or muscle weakness, dyspnoea, sleep difficulties, anxiety or depression, reduced lung capacity, memory/cognitive impairment (‘brain fog’), hyposmia/anosmia and the inability to exercise or work fully .
The mechanisms that explain these chronic symptoms after COVID-19 are not yet fully understood  and researchers worldwide are currently investigating such syndromes, with a well founded effort to address the underlying mechanisms, diagnosis and treatment under of condition as well as epidemiology in public and occupational environments [12,35,37,38].
From an occupational health perspective, strategies promoting the return to work for these workers will need to be implemented and could be similar to programmes developed for other chronic conditions. Moreover, several more severe sequelae following critical illness suggest the need for enhanced support by rehabilitation and occupational physicians with a multidisciplinary integrated approach [39–40]. The consequences of the epidemic must be evaluated over time for people who suffered from functional limitations before COVID-19, as their physical and mental condition may be modified by the epidemic and, specifically, the consequences of lockdown [12,41].
A further aspect that needs to be considered is to recognize the ’post-COVID-19 condition’ as an occupational disease and to compensate frontline health and other key workers living with its ‘debilitating’ effects [42–43].
SEVERE ACUTE RESPIRATORY SYNDROME CORONAVIRUS 2 VACCINES: EVALUATION OF EFFECTIVENESS WITH VARIANTS, BREAKTHROUGH INFECTIONS AND REINFECTIONS
SARS-CoV-2 vaccination provided substantial protection against infections, hospitalizations and deaths among those who had been vaccinated. Vaccination is an effective public health intervention with demonstrable impact, which will be critical in combination with nonpharmaceutical interventions to mitigate the COVID-19 pandemic .
SARS-CoV-2 vaccinations constitute a widely investigated aspect in the working population, especially among HCWs, with particular attention to infection rates [6▪,45–48], general preventive measures [40,49,50▪], testing strategies’ efficacy , vaccination adherence [51–55] and effectiveness [56–57].
Concerning vaccine efficacy and effectiveness, some critical issues quickly emerged regarding SARS-CoV-2 variants, breakthrough infections and reinfections.
Viruses like SARS-CoV-2 continuously evolve as changes in the genetic code (caused by genetic mutations or viral recombination) occur during genome replication; therefore, the concept of SARS-CoV-2 variants was introduced [58–60]. There are concerns that current therapies and vaccines will confer protection against new circulating SARS-CoV-2 variants because of possible resistance and vaccine ineffectiveness, respectively .
A few months ago, Ferrè et al. pointed out that data on the Omicron variant were scarce and that studies need to be carried out quickly to better define the threat this variant posed; reiterating, however, that protective measures and vaccination would nevertheless be the key elements in countering the spreading of the new variant and preventing new waves of severe COVID-19 cases and deaths. The same authors emphasized how, even at the level of social equality, it was mandatory to ensure access to vaccination worldwide, both to protect unvaccinated populations from severe COVID-19 cases and deaths and to prevent the virus from circulating freely, by rapidly accumulating mutations, which in turn can increase transmissibility and viral infectivity or might lead to new waves worldwide .
Breakthrough infections are closely related to a variant of interest and vaccination effectiveness. They are defined as the detection of SARS-CoV-2 on an RT-PCR assay performed in fully vaccinated people who may still get COVID-19. There are several relevant articles related to this issue in occupational settings; first of all, in healthcare, that reported breakthrough infections as early as a few months after the first vaccination rounds [63–65].
Regarding the effectiveness of natural immunity, reinfections, second, third, or more infections in individuals who have already had initial contact with the virus must be considered among HCWs [66–67] and workers from other occupational settings [68▪]. In a 2021 review, Murchu et al. reported that 11 large cohort studies were identified that estimated the risk of SARS-CoV-2 reinfection over time, including three enrolled HCWs and two that enrolled elderly care home residents. All studies reported low relative SARS-CoV-2 reinfection rates in individuals with prior evidence of infection, compared with those without, for up to 10 months. Hence, practical and scientific implications arise, such as the role of precautions (e.g. masks and distancing) or vaccine effectiveness and management, because of the evidence that both natural and vaccine immunity could be insufficient to provide lifelong immunity.
A further interesting research suggestion was provided by Stefanizzi et al.[70▪]. On the basis of Italian legislative indications about the concurrent administration of the third anti-SARS-CoV-2 and the influenza vaccines, the authors suggest the need to explore the immunological aspects related to this practice in order to support the updating of guidelines in Public and Occupational Health, and to guarantee both the best immunogenicity of COVID-19 vaccination and high vaccine coverage for influenza vaccination, particularly for high-risk groups in which the optimal immunogenicity of the COVID-19 vaccines must be reached.
All these aspects, with the rapid changes in the global pandemic epidemiological scenario, constitute aspects of being evaluated in governmental actions to protect public and occupational health and challenge research insights during the pandemic and postpandemic eras.
This rapid overview of the COVID-19 pandemic research gives insights into future scenarios that will possibly engage OHS practitioners and researchers, and which may represent ’branches of the same tree’.
First challenge to OHS is the need to re-assess the occupational risks, particularly in the biohazard realm. The assessment must include in-depth knowledge of how the virus spreads, the establishment, monitoring and effectiveness evaluation of procedural, technical and organizational prevention measures, and, last but not least, the appraisal of the new medical conditions and susceptibilities that the pandemic brought to light.
Indeed, new susceptible and vulnerable workers probably would need a dedicated Health Surveillance by occupational physicians; in fact, it could be likely necessary to perform specific health surveillance procedures, which could include tailored diagnostic assessments (e.g. extra cardiologic, pneumologic or immunologic laboratory and instrumental assessments), as well as to elaborate specific procedures, for example, when fitness for work becomes an issue for high-risk workers, such as those not vaccinated or those affected by comorbidities or post-COVID-19 conditions. It should also be underlined that the issue of the return to work (RTW) of individuals previously affected by COVID-19; the number of workers in such conditions is huge and, therefore, the OPs will very likely be confronted with RTW problems, which in turn need programs tailored to the specific work settings.
Scientific research can support this occupational physician's activity by also investigating little-explored areas, such as the role of cellular immunity, the identification of protective anti-SARS-CoV-2 antibodies cut-offs, or emergent clinical aspects, such as post-COVID-19 condition. The research must be of high-quality, targeted, and possibly generated by field studies, to produce data that can serve as guidance to all stakeholders involved in workers’ protection.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
REFERENCES AND RECOMMENDED READING
Papers of particular interest, published within the annual period of review, have been highlighted as:
▪ of special interest
▪▪ of outstanding interest
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