Vaccines against Covid-19
What do you know about the Covid-19 Vaccine ?
We provide clarity
Media, web, newspapers, television, radio, give repeatedly for days and days the news that "finally" we have the vaccine antiCovid-19 and with considerable emphasis and spectacularity has started in Europe to vaccinate people most vulnerable to the virus, ie health care professionals and the people in the aged homes.
But beyond what they inform us sometimes in a illusory and inexact way, what do we really know about the antiCovid-19 vaccine? How is it made, does it protect against the virus infection and transmission, is it safe and efficacious even for the viral virus mutations ?
Finally, we all know the word "vaccine", but do you know what vaccines are, how they are produced, what they contain, how they act, what is the immunity duration ?
Now let's start from this base in order to better understand what we are talking about.
What is a vaccine and what is it for?
A vaccine is designed to react the immune system against a specific infecting agent (virus or bacterium or parasite e.g. malaria), which can cause a serious and sometimes fatal disease.
With vaccination, the immune system comes into contact with the specific pathogen, without this causing the disease. If the vaccinated person in the future comes into contact with the same specific pathogen, the immune system will recognize it and will render it harmless.
In order to exercise the function of protection and defense, a vaccine must contain a portion of the infectious agent against which the immune system must react to defend itself.
The general rule is that vaccinations are only recommended if the benefit outweighs the risk of causing side effects.
The different types of vaccine:
1.Vaccines with the infectious agent alive but in attenuated form, ie. manipulated to make it less aggressive by reducing its ability to replicte. It is the most effective method of vaccination but requires caution, as it causes a strong and lasting immune response over a long period of time, so after 1-2 doses it is not necessary to make other recalls. The limitation is that these vaccines cannot be given if the immune system is weakened by diseases or drug treatments.
The live attenuated vaccines currently in use are: rubella, measles, ear mumps, varicella, herpes zoster, yellow fever.
2. Vaccines with the infectious agent inactivated or killed, so it is unable to replicate. These vaccines are less effective than the previous ones, in fact it is often necessary to do recall doses. The advantage is that they have few side effects and can also be administered to subjects with immune system weakened by disease or drug treatments.
The inactivated vaccines currently in use are: polio, hepatitis A
3. Purified vaccines containing one or more fragments of the infecting agent, necessary for the immune system to recognize it and activate protection. These vaccines have the advantage of stimulating the immune system in a targeted manner. Tolerance is good but recall doses are necessary.
The purified vaccines currently in use are: diphtheria, pertussis, tetanus, hepatitis B, HPV, influenza
4. Conjugated vaccines, for bacterial infections. They contain sugars (polysaccharides) of the infecting agent, conjugated with a transport protein to be recognized by the immune system. To obtain immunity, which lasts only for a few years, it is necessary to take several recall doses.
The conjugated vaccines currently in use are: pneumococcus, meningococcus
5. Vaccines with vector, a fragment of the infecting agent is coniugated into a virus or bacterium that does not cause disease in the humans, which acts as a vector-stimulator of the immune system. This is a fairly recent technique that has been used for Ebola vaccination.
Vaccines with a vector are some of those made against the COVID-19 virus
The COVID-19 vaccine:
For current vaccines against Covid-19, it cannot be said with certainty if they will reduce the risk of the virus transmission, which like all Coronaviruses is subject to frequent mutations as it from England or from South Africa.
The development of a safe and effective vaccine before it is administered to the peaple, requires several years of study-test from its development, 4 stages of clinical trials and finally its marketing.
In the emergency as it happened with Ebola and the Covid-19 pandemic, the timeframe is reduced and the effects of the vaccination, whether positive or negative, will only clearly evaluated over time: in the best of cases, 1-2 years are necessary.
1. The Covid-19 virus
Protection against all variants of COVID-19 requires a vaccine that can induce and maintain strong immune responses. For the time currently, the avaible vaccines are only to protect against complications of symptoms caused by the virus by slowing its replication.
2.The viral antigen included in the vaccines
The spikes on the surface of the Coronavirus (S or Spike protein) are the means by which Covid-19 attacks our cells. It is therefore necessary that the RNA of the virus is present in the vaccine to induce a response that blocks the Spike protein and therefore prevents the infection. This concept is in reality valid for all Coronavirus, not only for Covid-19.
3.Immune defenses to be induced
Covid-19 vaccine induces the immune production of high amounts of antibodies that neutralize the virus. In reality it is difficult, if not impossible, to obtain only the production of neutralizing antibodies, because at the same time non-neutralizing antibodies are developed, which can be dangerous.
4. Risk that the vaccine increases the severity of Covid-19
One risk of the vaccine is to induce , as mentioned above, the production of non-neutralizing antibodies, i.e. antibodies that can bind to the infecting virus but without neutralizing it. These antibodies (Antibody-Dependent Enhancement) can promote the entry of the virus into the cells and cause the reverse effect, i.e. they can favor the infection. This risk has already been found with the vaccine produced against SARS-Cov-1 virus and against MERS-CoV virus.
5. Vulnerable subjects
To induce with a vaccine an immune response in subjects who are weaker for diseases, drug treatments, old age, obesity, is more difficult than in healthy or younger subjects.
Covid-19 vaccines are produced with relatively new technologies and have been selected and licensed on the basis of scientific characteristics, people supply (number, timing), and commercial factors.
They are: vaccines with Covid-19 RNA (Pfeizer/Biontech, Moderna) and vaccines with Covid-19 RNA conjugated to a vector adenovirus (Oxford-AstraZeneca).
RNA vaccines (Pfeizer/BionTech, Moderna) contain a fragment of the Covid-19 virus RNA encapsulated in nanoparticles (80 nm in size) composed of lipids (fats). This type of vaccine is the most similar to the natural infection of the virus: it is a fragment of messenger code (RNA) of Covid-19 that induces an immune reaction against the Spike protein. Tolerance to nanoparticles depends on their composition; in the case of these vaccines, they are lipids similar to those of the human body and are metal-free. Polyethylene glycol (PEG) is present to improve vaccine storage.
The Oxford-AstraZeneca vaccine, in addition to a fragment of Covid-19 RNA, contains a genetically modified fraction of the cold adenovirus of chimpanzee . The chimpanzee cold adenovirus, inactivated so that it cannot multiply, acts as a vector for the viral RNA, contains DNA that becomes part of our genetic code.
The side effects of these vaccines can be locally (pain, redness, swelling at the site of inoculation) and/or generally (fever, fatigue, headache, muscle and joint pain). The average duration is 1-3 days and the occurrence depends on the reaction of the immune system of each subject, the age, the general state of health. In the subjects suffering from allergies, with a delicate immune system, who use immunosuppressive drugs or other drugs, in case of autoimmune diseases, the eventual vaccination must be valued by tests and precautionary measures.
To the control authorities of the various countries have been reported some cases of subjects submitted to vaccination against Covid-19, who had serious side effects or anaphylactic shock.
It 's too short time to have clear conclusions about the current anti-Covid-19 vaccines, only the time (years) will show whether they are effective and safe despite the mutations to which the virus is subject and whether they provide immunity over time to suppress the diffusion and the contagions.
Vaccinated subjects, in consideration of these unknowns, will continue to respect the rules of hygiene and social conduct followed until now, since at the moment we only know that the vaccine helps to protect against the symptoms caused by the infection. Even the period of the protection time is not known, nor is known whether the Covid-19 vaccines interact with the influenza vaccine.
At present, only hypothetical assumptions are made, mostly based on studies of animal models.
Available antiCovid-19 vaccines:
Studies are funded by the same multinational manufacturers
BNT162, Pfizer - BioNTech, vaccine with virus mRNA for Spike protein of SARS-CoV-2, encapsulated in lipid particles (nanoparticles).
mRNA-1273, Moderna, vaccine with virus mRNA for Spike protein of SARS-CoV-2
ChAdOx1, AstraZeneca, vaccines with chimpanzee cold adenovirus as vector and virus mRNA for Spike protein of SARS-CoV-2
