Is a single COVID-19 vaccine dose enough in convalescents ?

High Concentration of Anti-SARS-CoV-2 Antibodies 2 Years after COVID-19 Vaccination Stems Not Only from Boosters but Also from Widespread, Often Unrecognized, Contact with the Virus

This study follows 99 subjects vaccinated with Pfizer/BioNTech COVID-19 vaccines over two years, with particular focus on the last year of observation (between days 360 and 720). The response to the vaccination was assessed with Diasorin's SARS-CoV-2 TrimericSpike IgG. Screening for SARS-CoV-2 infection was performed with Abbott's SARS-CoV-2 Nucleocapsid IgG immunoassay. Data from questionnaires were also analyzed. Two years after the first vaccine dose administration, 100% of the subjects were positive for anti-spike SARS-CoV-2 IgG and the median antibody level was still high (3600 BAU/mL), dropping insignificantly over the last year. Simultaneously, a substantial increase in seropositivity in anti-nucleocapsid SARS-CoV-2 IgG was noted, reaching 33%. There was no statistically significant agreement between anti-N seropositivity and reported COVID-19. Higher anti-spike concentrations and lower COVID-19 incidence was seen in the older vaccinees. It was noted that only subjects boosted between days 360 and 720 showed an increase in anti-spike IgG concentrations. The higher antibody concentrations (median 7440 BAU/mL) on day 360 were noted in participants not infected over the following year. Vaccination, including booster administrations, and natural, even unrecognized, contact with SARS-CoV-2 entwined two years after the primary vaccination, leading to high anti-spike antibody concentrations.

COVID-19 vaccination challenges: A mini-review

The emergence of SARS-CoV-2 has led to the infection of many people across the globe, over six million deaths, and has placed an unprecedented burden on public health worldwide. The pandemic has led to the high-speed development and production of vaccines against the COVID-19, as vaccines can end the pandemic. At the beginning of the program, vaccinations were initially targeted only at high-risk groups, such as the elderly, those with comorbidities, or healthcare workers. Although most of the mentioned populations have received the two recommended doses, limited resources have left many authorities with an effective vaccine undersupply. Therefore, policies have been implemented to manage the available doses of the vaccines more efficiently. As there is no universally agreed consensus on this topic, we discuss the different recommendations and guidelines regarding the time interval between the two vaccine doses and explain the different scenarios for applying the two doses.

Potency of BNT162b2 and mRNA-1273 vaccine-induced neutralizing antibodies against severe acute respiratory syndrome-CoV-2 variants of concern: A systematic review of in vitro studies

BNT162b2 and mRNA-1273 are two types of mRNA-based vaccine platforms that have received emergency use authorization. The emergence of novel severe acute respiratory syndrome (SARS-CoV-2) variants has raised concerns of reduced sensitivity to neutralization by their elicited antibodies. We aimed to systematically review the most recent in vitro studies evaluating the effectiveness of BNT162b2 and mRNA-1273 induced neutralizing antibodies against SARS-CoV-2 variants of concern. We searched PubMed, Scopus, and Web of Science in addition to bioRxiv and medRxiv with terms including 'SARS-CoV-2', 'BNT162b2', 'mRNA-1273', and 'neutralizing antibody' up to June 29, 2021. A modified version of the Consolidated Standards of Reporting Trials (CONSORT) checklist was used for assessing included study quality. A total 36 in vitro studies meeting the eligibility criteria were included in this systematic review. B.1.1.7 (Alpha), B.1.351 (Beta), P.1 (Gamma), and B.1.617.2 (Delta) are four SARS-CoV-2 variants that have recently been identified as variants of concern. Included studies implemented different methods regarding pseudovirus or live virus neutralization assays for measuring neutralization titres against utilized viruses. After two dose vaccination by BNT162b2 or mRNA-1273, the B.1.351 variant had the least sensitivity to neutralizing antibodies, while B.1.1.7 variant had the most sensitivity; that is, it was better neutralized relative to the comparator strain. P.1 and B.1.617.2 variants had an intermediate level of impaired naturalization activity of antibodies elicited by prior vaccination. Our review suggests that immune sera derived from vaccinated individuals might show reduced protection of individuals immunized with mRNA vaccines against more recent SARS-CoV-2 variants of concern.

COVID-19 in Southeast Asia: current status and perspectives

Coronavirus Disease-2019 (COVID-19) has spread globally with catastrophic damages to the public health, social and economy since the beginning of the outbreak. In 2020, Southeast Asia proved that it could prevent the worst effects of a pandemic through the closure of activities and borders and movement restriction, as well as social distancing. Nevertheless, with the occurrence of the common variants of concern (VOCs), especially Alpha (B.1.1.7), Beta (B.1.351), Delta (B.1.617.2), Southeast Asia is facing a significant increase in the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infections. Now, the area also has the threats of the spreading out of the dangerous variant – Omicron (B.1.1.529) from other close countries or regions. COVID-19 countermeasures such as closures and social distancing seem to be insufficient. Moreover, Southeast Asia is being held back by a shortage of vaccines and other medical resources. This work focuses on describing the COVID-19 situation, the virus variants, and the coverage of COVID-19 vaccination in the area. We also provide perspectives on the COVID-19 vaccine distribution, protecting the economic capitals, developing the green zone, and the importance of finding more vaccine supplies in Southeast Asia.

Anti-Spike SARS-CoV-2 IgG Assessment with a Commercial Assay during a 4-Month Course after COVID-19 Vaccination

We intended to assess the humoral response induced by the Pfizer/BioNTech Comirnaty COVID-19 vaccine with commercially available immunoassays: anti-spike (S) IgG and IgM, and anti-nucleocapsid (N) IgG antibodies, over a 4-month course. One hundred subjects, including 15 COVID-19 convalescents, comprised the study cohort. The SARS-CoV-2 antibodies concentrations were measured on day 0' and 10', 20', 30', 60', 90', and 120' after the first dose administration. Over the course of the study, 100% of the participants developed and sustained anti-SARS-CoV-2 S IgG antibodies. The highest concentration, exceeding the quantification range of the test (2080 BAU/mL), was reached by 67% of the subjects on day 30'. The concentration of the antibodies remained stable between days 30' and 90' but was followed by a significant decrease between days 90' and 120'. The stronger and more persistent humoral response was noted for women. The COVID-19 convalescents developed higher antibody levels, particularly 10 days after the first Comirnaty dose. Twenty-three out of the eighty-five naïve vaccinees failed to develop a detectable IgM response. LIAISON® SARS-CoV-2 TrimericS IgG (DiaSorin S.p.A, Saluggia, Italy) may be useful in the assessment of the humoral response to the Comirnaty vaccine. In contrast, Abbott's anti-S SARS-CoV-2 IgM has a limited utility in this context.

Immune Responses against SARS-CoV-2-Questions and Experiences

Understanding immune reactivity against SARS-CoV-2 is essential for coping with the COVID-19 pandemic. Herein, we discuss experiences and open questions about the complex immune responses to SARS-CoV-2. Some people react excellently without experiencing any clinical symptoms, they do not get sick, and they do not pass the virus on to anyone else ("sterilizing" immunity). Others produce antibodies and do not get COVID-19 but transmit the virus to others ("protective" immunity). Some people get sick but recover. A varying percentage develops respiratory failure, systemic symptoms, clotting disorders, cytokine storms, or multi-organ failure; they subsequently decease. Some develop long COVID, a new pathologic entity similar to fatigue syndrome or autoimmunity. In reality, COVID-19 is considered more of a systemic immune-vascular disease than a pulmonic disease, involving many tissues and the central nervous system. To fully comprehend the complex clinical manifestations, a profound understanding of the immune responses to SARS-CoV-2 is a good way to improve clinical management of COVID-19. Although neutralizing antibodies are an established approach to recognize an immune status, cellular immunity plays at least an equivalent or an even more important role. However, reliable methods to estimate the SARS-CoV-2-specific T cell capacity are not available for clinical routines. This deficit is important because an unknown percentage of people may exist with good memory T cell responsibility but a low number of or completely lacking peripheral antibodies against SARS-CoV-2. Apart from natural immune responses, vaccination against SARS-CoV-2 turned out to be very effective and much safer than naturally acquired immunity. Nevertheless, besides unwanted side effects of the currently available vector and mRNA preparations, concerns remain whether these vaccines will be strong enough to defeat the pandemic. Altogether, herein we discuss important questions, and try to give answers based on the current knowledge and preliminary data from our laboratories.

Hybrid immunity: the immune response of COVID-19 survivors to vaccination

Hybrid immunity can become a turning-point opportunity to defeat the infection in context with the current pandemic scenario. Adopting policies aligned with the data mentioned above may be particularly beneficial for regions like Latin America. While this region shares only ~5% of the world population, it accumulates +16% of the ~200 million COVID-19 total cases, so far reported1. Acknowledging the reduced diagnostic capabilities of these countries, this entire area is probably one of the most affected globally, leading to one of the more numerous populations of convalescent people. From both an economic and pharmacological perspective, applying a one-dose regime of pertinent vaccines to convalescent individuals is sustainable5. As COVID-19 survivors may need just one vaccination to achieve high levels of protective immunity, massive antibody screening for SARS-CoV-2 spike antibodies could help prioritize and free up doses, optimize vaccine supply efficiency, and surpass problems linked to the current vaccine manufacturing bottleneck

SARS-CoV-2 Variants: A Synopsis of In Vitro Efficacy Data of Convalescent Plasma, Currently Marketed Vaccines, and Monoclonal Antibodies

We summarize here in vitro evidences of efficacy for convalescent plasma, currently approved vaccines and monoclonal antibodies against SARS-CoV-2 variants of concern (VOC: B.1.1.7, B.1.351, P.1, and B.1.617.2), variants of interest (VOI: B.1.427/B.1.429, P.2, B.1.525, P.3, B.1.526, and B.1.671.1), and other strains (B.1.1.298 and B.1.258delta). While waiting from real world clinical efficacy, these data provide guidance for the treating physician.

Anti-SARS-CoV-2 Antibodies Testing in Recipients of COVID-19 Vaccination: Why, When, and How?

Although universal vaccination is one of the most important healthcare strategies for limiting SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) circulation and averting the huge number of hospitalizations and deaths due to coronavirus disease 2019 (COVID-19), significant inter-individual variability of COVID-19 vaccines' efficacies has been described, mostly due to heterogeneous immune response in recipients. This opinion paper hence aims to discuss aspects related to the opportunity of monitoring anti-SARS-CoV-2 antibodies before and after COVID-19 vaccination, highlighting the pros and cons of this strategy. In summary, the advantages of anti-SARS-CoV-2 antibodies' testing in recipients of COVID-19 vaccination encompass an assessment of baseline seroprevalence of SARS-CoV-2 infection in non-vaccinated individuals; early identification of low or non-responders to COVID-19 vaccination; and timely detection of faster decay of anti-SARS-CoV-2 antibody levels. In contrast, potential drawbacks to date include an unproven equivalence between anti-SARS-CoV-2 antibody titer, neutralizing activity, and vaccine efficiency; the lack of cost-effective analyses of different testing strategies; the enormous volume of blood drawings and increase of laboratory workload that would be needed to support universal anti-SARS-CoV-2 antibodies testing. A potential solution entails the identification of cohorts to be prioritized for testing, including those at higher risk of being infected by variants of concern, those at higher risk of unfavorable disease progression, and subjects in whom vaccine immunogenicity may be expectedly lower and/or shorter.