Vaccination against coronavirus may need reminders.
7 August 2020 23: 00
Vaccination against the COVID-19 may require reminders: here is what it means
Institute of biomedical sciences, University of Brighton
THE SCIENCE IN HIS WORDS/The hope is reborn in the global race for the research against the coronavirus, while a number of vaccines are in development, offering the prospect of encouraging preliminary results. On the basis of what is already known, it seems likely that the vaccines are most effective against the SARS-CoV-2, the virus that causes the COVID-19 – require the use of boosters, and this can be regularly. What is it ?
When a pathogen enters the human body, our immune system saves the information and retains it in memory, in order to be able to lead a counter-offensive quickly if this germ represents. In most cases viral infections, that memory lasts a long time. But this is not always the case.
The underlying principle of all vaccinations is to give the subject a version of the germ that will not cause disease, but which will, however, in the memory of its immune system. This is achieved by various methods depending on the nature of the virus and the extent of our knowledge of that virus.
The two kinds of vaccines
Some vaccines are manufactured in order to neutralize the pathogen so as to render it safe when it is introduced, but that it is able to continue its natural life cycle. The idea being to stimulate a response close to that of the natural immune system in order to enroll in the long-term memory without making the subject ill.
This is the basis of the vaccine that is administered against measles, mumps, and rubella (MMR). It contains all the elements live, but inactivated, of each of these viruses. It is given to children in two doses at a few years interval, in the case where the vaccine does not work the first time, so we must “remember” the good memory of the immune system. It is not in the case of a booster vaccine as such, but rather of a second dose in order to avoid possible interference with other childhood infections, and, because the immune system of a preschool-age child is still in the development phase.
This approach MMR is made possible, because the virus of the measles, mumps and rubella are very widespread in the population, and that virologists have excellent knowledge on their interaction with the immune system. But it takes many years to create a live vaccine is safe and effective, and this is why, in the case of the SARS-CoV-2, the research teams are following different paths. In this case, one effective approach is to use a version dead of the virus, rather than a version live, but modified, as is the case for the MMR.
Inactivated vaccines against polio and the flu are both using versions died of the virus. The disadvantage of these vaccines is that the immune response doesn’t last, and that is why it is necessary to use reminders.
In the case of the seasonal flu, the mutations of the virus require a new vaccine every year, but even if the virus changed it or not, he should still use reminders to stimulate memory immune because the virus is not alive.
In the case of polio, most of the countries use an inactivated vaccine in their infant immunization programs, rather than the living administered orally. The fact that the disease has been nearly eradicated, it is assumed that the injection of a single dose per child should be enough to protect them when they start dating other people. But in the case of an epidemic, any person in the presence-close to other individuals in a local range should receive a booster vaccine.
What would a vaccine against the COVID-19 ?
The potential vaccine designed by the French firm Valneva, which will be manufactured in Scotland, is an inactivated vaccine. If it proves to be effective to protect us from SARS-CoV-2, this could certainly help reduce the spread of the virus.
In this case, recalls, would likely be required, perhaps on an annual basis, in order to guarantee the longevity of immune memory. In case of epidemic, all the people present in the infected area could receive a dose of the vaccine to limit transmission.
Another design of a vaccine is to extract the genetic code of the part of the virus that is known to stimulates an immune response, and insert it in a body holder, which may not cause disease.
The hepatitis B vaccine uses the code of the antigen found on the surface of the infectious particles of the virus. This code has been introduced into the genome of yeast and is harmless to manufacture a vaccine. As of its expansion, the yeast divides, communicates its properties to antigens on the surface of the virus, and encourages the body to provoke an immune response continues. Administered in three doses over a period of six months, this vaccine requires a booster after around five years for most individuals.
The vaccine of the COVID-19 developed by the team of the university of Oxford, and of which the initial results are promising, uses basically this approach, since the researchers have extracted the code for the spike protein of SARS-CoV-2 to the graft in a vector of harmless virus.
It is therefore possible that the initial schedule for any individual treated by this type of vaccine involves one or two booster doses, a few months after the first dose, as is the case for the vaccine for hepatitis B. We are not certain of the duration of immunity in the case of the COVID-19 in the framework of this strategy, but it could be measured in terms of years by analogy with hepatitis B. This may be enough to limit the spread of the SARS-CoV-2.