Latest Covid-19 Research: ‘Innovative’ Vaccine Candidate To New T-cell Test To Map Immune Response

From the efficacy shown by a new Covid-19 vaccine candidate in a clinical trial to a study about the waning effectiveness of existing vaccines — a look at the latest research on Covid-19

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New Delhi: With the SARS-CoV-2 virus evolving constantly, scientists across the world are working hard to understand the variant strains and their effect on those contracting it. Several studies are being conducted to understand the efficacy of existing vaccines, develop new and innovative vaccines, and understand the pathogenicity of SARS-CoV-2 variants. 

Here are some of the top global Covid-19 research shared this past week.

‘Innovative’ Vaccine Candidate

A new study conducted by researchers from the Vaccine Research Institute (VRI), CEA and Université Paris-Saclay highlights the efficacy in clinical trials shown by a new vaccine that they are working on and explains its working. The study was published in the Natural Communications Journal. 

The vaccine consists of a monoclonal antibody, which is an antibody made by cloning a unique white blood cell, and binds to only one substance. The monoclonal antibody stimulates dendritic cells, which are immune cells circulating throughout the body, by binding with a specific protein, resulting in a strong antibody and cellular response. The researchers have demonstrated this in other models of infection. As a Covid-19 vaccine candidate, the antibody must bind to a SARS-CoV-2 protein.

The scientists conducted experiments on convalescent animals (animals who no longer have clinical signs but have not returned to full function), who had been infected with SARS-CoV-2 virus six months ago, and studied the ability of their vaccine candidate to induce anti-Covid-19 booster responses with the help of models. They used both vaccinated and unvaccinated animals, along with control animals free from any previous infection, and found that the vaccinated animals showed a better ability to clear the virus in a shorter time, compared to the rest, on being newly exposed to the virus through the candidate vaccine. Thus, a better protection than natural immunity could be provided by the vaccine candidate.

The study demonstrates that this vaccine, developed from the initial SARS-CoV-2 strain, induces an antibody response capable of neutralising new variants. The antibody response neutralises the Alpha variant (B.1.1.7) in a very effective manner, and the Beta variant (B.1.351) quite significantly.

The vaccine, without an adjuvant (a substance enhancing the body's immune response to a foreign object), restimulates the production of neutralising antibodies capable of binding to the virus during reinfection, concludes the study.

Quick Method Found To Measure T-cell Immune Response To SARS-CoV-2 

Researchers from various universities have found a simple and quick method to measure the T-cell immune response to SARS-CoV-2. 

Their study, published in the Journal of Clinical Investigation, explains that in a coordinated immune response against SARS-CoV-2, T-cells and antibodies play an important role, and this new method will provide additional help to scientists in monitoring and assessing T-cell responses in Covid-infected individuals, and also aid them in testing and verifying the effectiveness of vaccines. 

The researchers conducted a test, Cytokine Release Assay (CRA), on the blood samples of people who had received Covid-19 vaccine, and those who had recovered from Covid-19. The scientists introduced small fragments of the SARS-CoV-2 spike protein into their samples, in response to which the chemical signals called cytokines were released by the T-cells, making it much easier to detect and quantify these cells, without the use of specialised equipment. 

The scientists say that the CRA test will help define the correlation between T-cells and antibodies in providing protection against SARS-CoV-2, and that this will be beneficial for Covid-19 vaccine development.

Effectiveness Of Covid-19 Vaccines Wanes Over Time: Study

A team of physicians and public health experts at the University of California, San Diego, wrote a letter to The New England Journal of Medicine, which was published on September 1, 2021, highlighting the measurements of Covid-19 mRNA vaccine effectiveness among health workers at UC San Diego Health. 

This was notably during the time the highly transmissible Delta virus variant emerged, and when the state's mask mandate ended, allowing fully vaccinated people to go out in public without wearing masks. 

The letter states that the effectiveness of both Pfizer and Moderna mRNA Covid-19 vaccines, which were granted emergency use authorization by the Food and Drug Administration in December 2020, decreased over time. From March through June 2021, vaccine effectiveness against symptomatic infection decreased from more than 90 percent to about 65 percent by July, the authors note. 

When the Delta variant is taken into consideration, the vaccine effectiveness for mildly symptomatic disease was considerably lower, and decreased within six to eight months of recieving the second dose, according to Francesca Torriani, co-senior author of the study. 

With California's mask mandate ending and Delta variant emerging in July 2021, more people, belonging to the highly vaccinated population, were diagnosed with SARS-CoV-2 infection. Co-author Nancy Binkin said that these factors resulted in the dramatic change in vaccine effectiveness from June to July. Another co-author said in the letter that the Delta-infected young children, aged five to 11, were infecting their parents, unlike what was experienced with other variants.

The letter mentions that the infection rates in healthcare workers who had been fully vaccinated in January and February were higher than those who were vaccinated in March through May, indicating that vaccine effectiveness was associated with the passage of time.

Co-senior author Shira Abeles said in the letter that the findings highlight the importance of reinstating measures such as indoor masking, intensive testing strategies, and the necessity of boosting vaccination rates.

Hospitalisation Risk Due To Delta Variant Twice That Of Alpha Strain

A new UK study, published in The Lancet Infectious Diseases Journal, has said that the risk of hospitalisation in people infected with the SARS-CoV-2 Delta variant is twice that of people infected with the Alpha variant. More than 40,000 cases from England between 29 March and 23 May 2021 were studied. 

The most accurate way to determine the Delta variant is whole-genome sequencing as it determines the entire DNA sequence of an organism's genome at a single time. Cases confirmed by this method of sequencing were included in this study, making it the first of its kind. 

Compared with the Alpha variant, the risk of being admitted to a hospital or attending it for emergency care within 14 days of being infected with the Delta was 1.45 times greater. 

Dr Gavin Dabrera, one of the lead-authors of the study, said most of the people included in the study were unvaccinated, and since the Delta variant accounts for more than 98 per cent of Covid-19 cases in the UK, it is essential for the people who haven't received the two doses of vaccine to get vaccinated at the earliest. 

The study states that the Alpha variant, first identified in Kent, UK, had previously gained dominance worldwide and that the Delta variant, first reported in India in December 2020, was up to 50 per cent more transmissible than the Alpha variant.

Since only 1.8 per cent of the people involved in this study were fully vaccinated, the study primarily tells us about the risk of hospitalisation for the unvaccinated or partially vaccinated population. Hence, it is not possible to statistically decipher from this study, how the hospitalisation risk for vaccinated people infected with Alpha and Delta variants, after receiving both doses, are different from each other.

Some of the limitations of this study included lack of access to the pre-existing health conditions of the patients, which affect the risk of severe illness from Covid-19, the authors note.