Symptom presentation among SARS-CoV-2 positive cases and the impact of COVID-19 vaccination; three prospective household cohorts (preprint)

OBJECTIVEUsing data from European prospective household studies, we systematically compared the symptom burden of the wild-type and Alpha variant infected individuals versus the Omicron BA.1 and BA.2 infected individuals across paediatric and adult age-groups. In addition, we measured the impact of COVID-19 vaccination on the Omicron symptom burden. METHODSThe household transmission studies were conducted during the wild-type and Alpha period (April 2020 to April 2021) and the early Omicron BA.1 and BA.2 dominant period (January to March 2022). All three studies used similar protocols. Households were prospectively followed from detection of the first SARS-CoV-2 index case until at least day 21 including (repeated) PCR testing, paired serology and daily symptom reporting for all household members. To avoid possible index-case ascertainment bias, we restricted analyses to secondary household cases. Age-stratified SARS-CoV-2 symptom burden was compared for wild-type/Alpha versus Omicron infections and for primary versus primary plus booster series vaccinated adult cases. FINDINGSIn total 216 secondary cases from wild-type/Alpha, and 130 from the Omicron period were included. Unvaccinated children <12 years experienced more symptoms and higher maximum and cumulative severity scores during the Omicron compared to the wild-type/Alpha period (p=0.004, p=0.011 and p=0.075, respectively). In adults, disease duration and maximum and cumulative severity scores were reduced during the Omicron period. Adjusted for age, gender and prior immunity Omicron was associated with lower odds for loss of smell or taste (Odds Ratio [OR]: 0.14; 95%CI 0.03-0.50), and higher, but non-significant odds for upper respiratory symptoms, fever and fatigue (ORs varying between 1.85-2.23). Comparing primary versus primary plus booster vaccinated adult cases during the Omicron period no differences were observed in disease severity or duration (p[≥]0.12). INTERPRETATIONIn children, the Omicron variant causes higher symptom burden compared to the wild-type/Alpha. Adults experienced a lower symptom burden possibly due to prior vaccination. A shift in most frequently reported symptoms occurred with a marked reduction in loss of smell or taste during the Omicron period. An additional effect of booster vaccination on symptom severity in infected adults compared to primary series only, could not be demonstrated.

VIROLOGICAL AND IMMUNOLOGICAL FEATURES OF SARS-COV-2 INFECTED CHILDREN WITH DISTINCT SYMPTOMATOLOGY (preprint)

BACKGROUND: Despite SARS-CoV-2 immunizations have started in most countries, children are not currently included in the vaccination programs, thus it remains crucial to define their anti-SARS-CoV-2 immune response in order to minimize the risk for other epidemic waves. This study seeks to provide a description of the virology ad anti-SARS-CoV-2 immunity in children with distinct symptomatology. METHODS: Between March and July 2020, we recruited 15 SARS-CoV-2 asymptomatic (AS) and 51 symptomatic children (SY), stratified according to WHO clinical classification. We measured SARS-CoV-2 viral load using ddPCR and qPCR in longitudinally collected nasopharyngeal swabs samples. To define anti-SARS-CoV-2 antibodies we measured neutralization activity and total IgG load (Diasorin). We also evaluated antigen-specific B and CD8+T-cells, using a labelled S1+S2 protein and ICAM expression, respectively. Plasma protein profiling was performed with Olink. RESULTS: Virological profiling showed that AS had lower viral load at diagnosis (p=0.004) and faster virus clearance (p=0.0002) compared to SY. Anti-SARS CoV-2 humoral and cellular response did not appear to be associated with the presence of symptoms. AS and SY showed similar titers of SARS-CoV-2 IgG, levels of neutralizing activity, and frequency of Ag-specific B and CD8+T-cells. Whereas pro-inflammatory plasma protein profile was associated to symptomatology. CONCLUSION: We demonstrated the development of anti-SARS-CoV-2 humoral and cellular response with any regards to symptomatology, suggesting the ability of both SY and AS to contribute towards herd immunity. The virological profiling of AS suggested that they have lower virus load associated with faster virus clearance.

Analytical and clinical performances of a SARS-CoV-2 S-RBD IgG assay: comparison with neutralization titers (preprint)

Background SARS-CoV-2 serology presents an important role in understanding the virus epidemiology, in vaccine prioritization strategies and in convalescent plasma therapy. Immunoassays performances have to be accurately evaluated and correlated with neutralizing antibodies to be used as a surrogate measure of neutralizing activity. We investigate the analytical and clinical performance of a SARS-CoV-2 RBD IgG assay, automated on a high throughput platform, and the correlation of the antibodies (Ab) levels with the plaque reduction neutralization (PRNT 50 ) Ab titers. Methods A series of 546 samples were evaluated by SARS-CoV-2 RBD IgG assay (Snibe diagnostics), including 171 negative and 168 positive SARS-CoV-2 subjects and a further group of 207 subjects of the COVID-19 family clusters follow-up cohort. Results Assay precision was acceptable at low and medium levels; linearity was excellent in all the measurement range. Considering specimens collected after 14 days post symptoms onset, overall sensitivity and specificity were 99.0% and 92.5%, respectively. A total of 281 leftover samples results of the PRNT 50 test were available. An elevated correlation was obtained between the SARS-CoV-2 RBD IgG assay and the PRNT 50 titer at univariate (rho = 0.689) and multivariate (rho = 0.712) analyses. Conclusions SARS-CoV-2 S-RBD IgG assay achieves elevated analytical and clinical performances, and a strong correlation with sera neutralization activity.

Prioritizing the first doses of SARS-CoV-2 vaccine to save the elderly: the case study of Italy (preprint)

Many countries are currently facing high mortality caused by the circulation of SARS-CoV-2 among the elderly not yet vaccinated. Vaccine shortage poses relevant challenges to health authorities, called to act in a timely manner, and with scarcity of vaccine, and data. We have developed a model for estimating of the impact of vaccination on the mortality of the elderly following a schedule of mRNA SARS-CoV-2 vaccine that prioritize first dose administration, as alternative to the standard schedule of two doses administered 3 to 4 weeks apart. We studied the Italian scenario, considering it representative of other Countries facing similar conditions in terms of virus circulation, mortality, and vaccine shortage, in the period from February 10 to April 14 2021. Under different conditions of quantity of vaccine administration, the schedule prioritizing first doses showed always significant increase of protected individuals, and a decrease of deaths, up to 19.8% less than the standard schedule. These findings support the vaccination option of prioritizing first dose in the elderly until vaccine supplies are adequate.

Virological and Immunological Features of SARS-CoV-2 Infected Children Developing Specific and Neutralizing Antibodies (preprint)

As the global COVID-19 pandemic progresses and with the school reopening, it is paramount to gain knowledge on adaptive immunity to SARS-CoV-2 in children in order to define possible immunization strategies and reconsider pandemic control measures. We analyzed anti-SARS-CoV-2 antibodies (Ab) and their neutralizing activity (PRNT) in 42 COVID-19-infected children 7 days after symptoms onset. Individuals with specific humoral responses presented faster virus clearance, and lower viral load associated to a reduced in vitro infectivity. We demonstrated that the frequencies of SARS-CoV-2 specific CD4-CD40L+ T-cells and Spike specific B-cells were associated with the anti-SARS-CoV-2 Ab and the magnitude of neutralizing activity. The plasma proteome confirmed the association between cellular and humoral SARS-CoV-2 immunity, with PRNT+ patients showing higher viral signal transduction molecules (SLAMF1, CD244, CLEC4G). This work shed lights on cellular and humoral anti-SARS-CoV-2 responses in children which may drive future vaccination trials endpoints and quarantine measures policies.Funding: This work was made possible by support from Bambino Gesù Children’s Hospital ricerca corrente 2020 to NC and ricerca corrente 2019 to PP, by PENTA and by Fondazione Cassa di Risparmio di Padova e Rovigo, Progetti di Ricerca Covid-19 (ADR participant).Conflict of Interest: The authors declare no competing interests.Ethical Approval: Local ethical committee approved the study and written informed consent was obtained from all participants or legal guardians.

Frequent testing regimen based on salivary samples for an effective COVID-19 containment strategy (preprint)

Rapid and accurate diagnostic tests are essential for controlling the ongoing COVID-19 pandemic. Although the current gold standard involves testing of nasopharyngeal swabs specimens by nucleic acid amplification test, such as real-time reverse-transcription polymerase chain reaction (rRT-PCR) to detect the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), it presents several limitations that ultimately may translate into a bottleneck in the surveillance regimen. New strategies based on frequent testing using less invasive specimens are urgently needed for containment of the infection. Rapid antigen assay using saliva as a reliable alternative to nasopharyngeal swabs should be proposed as a valuable part of the overall testing strategy.