Why vaccines may be essential to end the pandemic
If the transmission of a pathogen is reduced, as a consequence of a high proportion of the population being immune, group or herd immunity can be achieved.
An indirect protection that we can only reasonably achieve against SARS-CoV-2 through vaccination, as evidenced by the fact that countries that chose to allow the population less vulnerable to the disease to become infected have changed their strategy.
Achieving group immunity against covid-19 is therefore essential to protect those who cannot be vaccinated: people with clotting problems, immunosuppressed, severe allergies, pregnant women, etc.
What are vaccines?
The first two authorized by the EU (Pfizer-BioNTech and Moderna) are based on a lipid-encapsulated messenger RNA to facilitate their entry into our cells. This RNA is like the “software” of the coronavirus, it carries the information necessary for our cells to make the spike (S) protein, which SARS-CoV-2 uses to enter our cells.
The Oxford-AstraZeneca vaccine is based on a chimpanzee adenovirus incapable of replicating in human cells, which has been “emptied” and which carries the information that codes for protein S in the form of DNA. The greater stability of this nucleic acid allows this vaccine to be stored in a refrigerator, while those from Pfizer-BioNTech and Moderna require deep freezers.
However, the effectiveness of the Oxford-AstraZeneca can be reduced if we have been previously infected with a human adenovirus, since our immune system could “attack” the vaccine. In any case, by synthesizing protein S, vaccines allow our immune system to develop specific B and T lymphocytes, which will produce antibodies and kill infected cells.
Are covid-19 vaccines safe?
Yes. Both RNA and chimpanzee adenovirus are practically harmless. In addition, the safety of any vaccine is evaluated, without exception. Of the nearly 100 vaccines that have been evaluated preclinically, a total of 64 candidates have been evaluated in human clinical trials.
They confirm that they stimulate the immune system and their safety is evaluated, in different phases in which the number of volunteers is progressively increased, from a few (phase I), to later inoculate thousands (phase III) with the vaccine or a placebo, in which different groups (age, sex) are also established, its efficacy is evaluated and an attempt is made to find rare adverse effects.
How effective are they?
The efficacy of messenger RNA vaccines is around 95% . It is surprisingly high. Until last year, there were only a few examples of clinical trials with RNA vaccines (against rabies, flu, or chikunguya), and only one of them, a vaccine against the Zika virus, had reached phase II.
AstraZeneca’s vaccine is up to 90% effective when the amount of vaccine is reduced in the first dose, something we know from a discovery.
Although the efficacy data is very clear, its effectiveness has yet to be determined. Will they be able to protect the entire population, including those with previous pathologies and people who cannot be vaccinated? Ultimately, will they be effective in generating herd immunity?
How is it possible to have developed vaccines so quickly?
We are amazed that in times of pandemic “science advances a lot.” But scientists always walk on the shoulders of giants. Edward Jenner carried out the first vaccination against smallpox more than two centuries ago and it has been 30 years since certain therapeutic indications in an RNA vaccine were described.
Thanks to numerous efforts, the time required for us to use this technology today has been reduced. Among them, Katalin Karikó, who in 2005 described how to reduce its adverse inflammatory effects. Another key factor has been the urgent release of public and private research funds for COVID-19. This has reduced the terms from months to days.
It is also key that several laboratories have competed with each other to reach the goal first. In addition, it has been essential that they have combined phases I and II in clinical trials simultaneously: vaccinate as many people as possible as soon as possible and that they live in regions with a very high incidence, which will ensure that a reasonable number of volunteers end up infected.
Is it true that they have as many adverse effects as we have read?
Like all medicines, obviously vaccines can have adverse effects. There are people who are concerned because we do not know its long-term effects from having been developed so quickly. However, a vaccine is not a conventional medicine that we take repeatedly over time and can cause long-term effects (for example, prolonged consumption of aspirin can cause gastric damage).
By their very nature, if vaccines give adverse effects, these will be immediate or will appear in the first two weeks, when our immune system is training. To date, we have more than 10 million people vaccinated with the Pfizer-BioNTech vaccine and there have been hardly any adverse effects , including a single case of encephalitis, which, however, has been very high in the media. We can therefore be calm and safe and ignore the alarmist news that reaches us through social networks.
Can vaccines make me transgenic?
Surely many have read or thought that, being an RNA vaccine, I run the risk of becoming transgenic. Nothing is further from reality. RNA is a highly unstable molecule (that is why vaccines should be kept at -80ºC), as it degrades very easily.
As soon as it enters our cells and they begin to synthesize proteins, RNA is degraded. In fact, I wish it were so easy to go transgenic with an RNA vaccine. In this way, we would not have to resort to the Nobel Prize-winning CRISPR-Cas9 technique to modify the genome.
However, there are cases of transgenic humans, such as patients with certain lymphomas who are treated with “CAR T-cell” therapy, where the patients’ lymphocytes are modified so that they can destroy the cells. tumors with an approximate cost of € 500,000 per patient. In short, I wish it were so easy to modify the genome of an organism, so we can be calm and safe with vaccines, which no, they will not modify our DNA.
If I get vaccinated can I get it?
There has been a lot of talk about cases of reinfection after having passed the disease, but as we have already discussed, these are a minority. These days, however, the alarm of infected elderly people was jumping, despite having been vaccinated.
Here we have to take into account two factors. The first is that, although they had received the first dose, the peak of immunity was not reached until 10 days after the second dose, so they were not fully immunized.
On the other hand, vaccinated people do not develop a force field around them on which the virus will bounce. Obviously, the virus will enter these people even after they have completed their immunization. And your CRP may be positive. But they will not develop the disease. To give an example, a person immunized against mumps cannot pass the disease again, although we can find viruses inside him if he lives with someone who is passing them.
Finally, it must be remembered that the efficacy of these vaccines is 95%, so there will be a minimum number of people for whom the vaccine is not effective due to various factors.
Will these vaccines work against the new variants of the virus?
We mistakenly tend to compare SARS-CoV-2 to the flu, as both are respiratory and life-threatening viruses. However, they are nothing alike. Although both are RNA viruses, SARS-CoV-2 has a mechanism that the flu does not have and that allows it to “repair” replication errors, so its mutation rate is much lower. But it is that, in addition, the flu has 7 genes, each one in a single RNA chain. This is the main asset of the flu, its ability to recombine if a person becomes infected with two different variants.
In fact, the flu as such does not exist, but there are multiple different viruses and that is why every year we are vaccinated with the 4 variants that we assume will reach the northern hemisphere. However, all of the SARS-CoV-2 genes are on a single RNA strand, making it impossible for it to recombine.
That said, the virus is slowly mutating, but its mutation rate is very low. However, everything seems to indicate that the vaccines will continue to be effective against the new variants that are emerging. This is because vaccines induce immunity against all protein S, so even if there are small changes in it, there will be more cells and antibodies capable of recognizing it. It is highly unlikely that the virus will mutate so much as to render vaccines useless.
However, and in the unlikely event that this should happen, the technology of these vaccines is already developed, so it would take just a month to readapt the vaccines to the new variants to make them more effective if necessary.
Will I need to get vaccinated against COVID-19 again in the future?
To this day we do not know , since the virus has been with us for a year, so we cannot predict how long immunity will last.
However, we know that the closest relative to this virus is SARS-CoV-1, which caused the SARS epidemic in 2003. Well, 17 years later, patients who had the disease are still immunized.
Therefore, there is no reason to think that the immunity induced by SARS-CoV-2 (either natural -infection- or artificial -vaccine-) is going to be different and not durable. Despite this, if immunity were to decline over time, it would quickly recover with booster doses, as with other vaccines. Therefore, to answer this question we still have to wait.
David Bernardo, Teaching and Researcher Staff in Human Immunology. Institute of Molecular Biology and Genetics (IBGM), University of Valladolid-CSIC and CIBEREHD, University of Valladolid and Salvador Iborra Martín, Teaching and Research Staff. Immunology and infection, Complutense University of Madrid
This article was originally published on The Conversation. Read the original.
