(Selected Tables and Figures referenced, but not present in this blog
can be found in their corresponding Science Version blogs)
Vaccination is the act of getting a vaccine, usually in the form of an injection into the arm of a person (immunization) to protect against a disease. Testing for an effective vaccine is done in 3 phases from animals to humans to if it produces an immune response. if the vaccine protects against the coronavirus in at least 50% of vaccinated people it is considered effective and regulators decide whether to approve the vaccine or not. The mRNA vaccines (Pfizer and Moderna) proved highly effective at 95% and 94%, respectively, and received immediate EUA in January 2021.
Vaccination levels must produce a threshold called “herd immunity” to achieve “R-Naught” (RO) or SIR (“susceptible-infectious-recovered” formulation), a factor that determines the transmissibility of the pathogen. It denotes the average number of secondary cases of an infectious disease that 1 case would generate in a completely susceptible population. That is, when one infected person infects greater than one other person, a potential exponential increase in infections results leading to an epidemic or pandemic. If, however, transmission on average remains below an RO of one person, this will result in a decreasing spread in infection and eventually into a majority of the population (an estimated 70% to 80% needed) to produce “herd immunity.”
In the absence of a vaccine, developing herd immunity to an infectious agent requires large amounts of people actually being infected, developing antibodies to the infectious agent and thus becoming immunized against future infection. Assuming that immunity is achieved (and long-lasting?), a very large number of people must be infected to reach the 70% to 80% herd immunity threshold required. During this process, mortality of certain infections like SARS-CoV-2 could reach unacceptable levels as occurred in Sweden where herd immunity was attempted. Nor does a pathogen magically disappear when the herd immunity threshold is reached. Rather, it only means that transmission begins to slow down and that a new epidemic is unlikely to start up again. An uncontrolled pandemic could continue for months after herd immunity is reached, potentially infecting many more millions in the process. These additional infections are what epidemiologists refer to as “overshoot.”
Researchers are genetically sequencing the entire human immune (the "immunome") system, a system billions of times larger than the human genome. The goal is to encode the genes (the antibody-encoding genes from Blog #7) responsible for circulating B cell receptors. This can provide potentially new antibody targets for vaccines and therapeutics that work across populations. The Human Vaccines Project seeks to define the genetic predisposition of people’s ability to respond and adapt to an immense range of diseases. The study specifically looks at one part of the adaptive immune system, the circulating B-cell receptors that are responsible for the production of antibodies, considered the primary determinant of immunity in people. The receptors form unique sequences of nucleotides (DNA base compounds) known as receptor “clonotypes.” This creates a small number of genes that can lead to an incredible diversity of receptors, allowing the immune system to recognize almost any new pathogen. This Project marks a crucial step toward understanding how the human immune system works, setting the stage for developing next-generation health products, drugs, and vaccines through the convergence of genomics and immune monitoring technologies with machine learning and artificial intelligence (AI).
Comments