Researchers in Sweden conducted a cohort study of 2149 healthcare professionals regarding symptoms consistent with long COVID-19 after mild infection for up to 8 months. Of the participants, 323 were anti-SARS-CoV-2 IgG seropositive and 1072 were seronegative at baseline and participants with previous severe disease and those who developed seropositivity during the study were excluded. 71/323 (22%) seropositive and 254/1072 (24%) seronegative participants reported underlying chronic disease. 26% of seropositive versus 9% of seronegative participants reported at least one persistent symptom that lasted at least two months (RR, 2.9 [95% CI, 2.2-3.8]) and 15% of seropositive versus 3% of seronegative participants reported at least one symptom that lasted at least 8 months (RR, 4.4 [95% CI, 2.9-6.7]) (Table). The most common symptoms in the seropositive group were anosmia, dyspnea, and fatigue with these symptoms being reported as significantly affecting work life, home life, and social life in 8%, 12%, and 15% of seropositive individuals respectively. These results indicate that low risk individuals with mild COVID-19 experience significant long-term symptoms.

Investigators at the Institute for Basic Science in South Korea analyzed nasal epithelial samples from humans and nonhuman primates infected with SARS-CoV-2. By combining immunofluorescence staining and single cell RNA-sequencing, they found high levels of viral proteins in the setting of low levels of mRNA with proteins generally localized to the apical side of multiciliated cells (Figure 2, B-G) suggesting that mRNA levels poorly correlate to cellular localization. Additionally, they found that SARS-CoV-2 replication was localized to these nasal multiciliated cells when compared to oral squamous cells (Figure 4, B and C). While the findings suggest early replication in shedding epithelia of the nasal cavity, the lack of inclusion of glandular epithelial cells warrants study of these cells as potential points of replication for the virus.

In a literature review of 30 studies, a multidisciplinary team of researchers associated several Canadian universities discuss COVID-19 transmission risk in essential occupations such as healthcare, retail, manufacturing, and agriculture. In these occupations, the main issues reported that increase risk of transmission were lack of PPE, inadequate health insurance, physical proximity to each other, housing conditions, and many more (Table 3). In addition, COVID-19 rates also increase with structural inequities, discrimination, and mental health issues. These findings suggest that public systems such as healthcare, legislation, workplace environment, and community network for must change for the better (Table 4).

A prospective cohort study conducted by researchers affiliated with multiple medical centers in Israel included 84 breastfeeding women who received 2 doses of the Pfizer-BioNTech vaccine between December 23, 2020 and January 15, 2021 and found positive levels of anti-SARS-CoV-2-specific IgA antibodies (ABs) in breast milk in 61.8% of samples 2 weeks after the first dose, 86.1% after 4 weeks, and 65.7% after 6 weeks as well as anti-SARS-CoV-2-specific IgG ABs in 91.7% at week 5 and 97% in weeks 5-6 (Figure 1). There were no serious adverse events reported during the study period but 47 (55.9%) and 52 (61.9%) reported vaccine-related adverse events after the first and second dose, respectively (Table 1). These findings suggest the antibodies found in breast milk showed strong neutralizing effects and potentially provide a protective effect in infants as protection against SARS-CoV-2 infection.

A cohort study performed by researchers from SciLifeLab and Danderyd Hospital in Sweden studied COVID-19-related long-term symptoms in health care professionals in Stockholm, Sweden. They found that low-risk individuals with mild COVID-19 reported a wide array of long-term symptoms (Table 1), which disrupted their work, social, and home life (Figure 1). The symptoms were self-reported, and the research team indicated that recall bias and the subjective rating of symptoms were potential study limitations.