I read with interest, and some concern, the article by Dr. J. M. Hermoso de Mendoza Urrizola published in DdN on 28/12/2020. I have known the doctor for years and I have no doubt of his professionalism and good work as a physician. I agree with him on the need to inform the patient with absolute clarity, with the corresponding informed consent and on the non-obligatory nature of vaccination, but I disagree on how he has approached some of his considerations on vaccination against COVID-19.

The vaccine that has begun to be distributed is based on RNA technology. It is true that this is the first time that it has been authorized for use in humans, but RNA vaccines have been worked on for more than ten years, they have been essay against other viruses and against cancer, and phase I clinical trials have even been carried out previously. It has been said that these messenger RNA-based vaccines can modify the functions of our genome and cause unknown and irreparable damage. However, the truth is that there is no data to suggest that these subject vaccines can alter our DNA. Natural infection with coronaviruses also produces millions of messenger RNAs and poses no risk to our DNA. In fact, no coronavirus gene has ever been detected inserted into our genome. The RNA molecule is very fragile, the time it remains in cells is very short and it disappears easily. Moreover, RNA does not meet DNA: DNA is found in the cell nucleus and messenger RNA in the cytoplasm. For the messenger RNA to become integrated into the nuclear DNA, it must have specific sequences or signals, which the vaccine does not have. Finally, in the hypothetical case that the vaccine RNA were to integrate into the genome of one of our muscle cells, the biological effect on our organism would probably be nil. RNA vaccines do not modify our genome because they do not affect our germ cells or gametes. At summary, there is no scientific evidence based on what we know about molecular biology that indicates that the messenger RNA used in COVID-19 vaccines may have the capacity to alter our genome. Nor is there any indication that these vaccines pose a risk to fertility. In fact, animal experiments have been performed and no related effects on female fertility, gestation or embryonic, fetal or offspring development have been observed.

Regarding side effects, the technical data sheet of the vaccine can be consulted on the Internet at the Spanish Agency of Medicines and Health Products. There it is clearly indicated that it is a drug subject to additional monitoring. Indeed, the approval has been conditional because we must not forget that we are in status of international health emergency, a pandemic that has already cost more than 1,700,000 deaths only during this year 2020. Safety has been evaluated in 21,744 participants in the clinical phases who received at least one dose of the vaccine. Like all vaccines, it can produce mild adverse effects, although not all people will experience them. Most of these mild effects are due to the fact that the vaccine works, that it stimulates our immune system. Very common mild side effects (more than 1 in 10 people): pain and swelling at the injection site, tiredness, headache, muscle and joint pain, chills and fever. Frequent effects (up to 1 in 10 people): redness at the injection site and nausea. Rare effects (up to 1 in 100 persons): enlarged lymph nodes, malaise, pain in the extremity, insomnia, itching at the injection site. Rare effects (up to 1 in 1000 persons): temporary paralysis of one side of the face. Frequency not known: severe allergic reaction. If reading all this makes you uneasy, I recommend that you go right now to your medicine cabinet and read the package insert for ibuprofen. After all, all medicines have side effects and pose a risk. Especially if we take into account that each of us can respond differently (that is why personalized medicine is so important).

It is true that we do not yet have data of possible long-term effects deadline, simply because there has not been enough time. Therefore, what is known as phase IV of pharmacovigilance is now beginning, in which safety (possible very rare side effects that are impossible to detect with thousands of volunteers but that become evident when they are test in millions of people), and its effectiveness (whether it really works in controlling the epidemic) continue to be evaluated. Therefore, we should not be surprised that, as with other drugs, a vaccine may be withdrawn from the market at a later date if it is found to be unsafe or ineffective.

Finally, remember that the evaluating agencies also evaluate the risk-benefit ratio: the benefit of the vaccine should be reasonably greater than the risk of the coronavirus. One should evaluate what one prefers: more than 74,000 deaths caused by the coronavirus and its "collateral effects" in Spain or some possible serious side effect of the vaccine. The probability of catching SARS-CoV-2, of getting sick and having serious and even fatal consequences, and of infecting others, is greater than the possible side effects that the vaccine may have. I get vaccinated to protect my daughter who is pregnant, my grandchildren who are young and my mother-in-law who is over 80 years old.

We are facing a silent and dangerous virus, for which the population is not previously immunized, which is transmitted through the air via aerosols, which can be transmitted by people before they present symptoms and even by people who will never manifest symptoms and whose infective dose is probably very high leave. It is a real time bomb, very difficult to control. Only vaccines will get us out of it as soon as possible. In 2020, this virus has caused more than 74 thousand deaths in Spain alone, schools and universities have been closed, it has destroyed thousands of jobs and sunk our Economics, it has changed our habits, thousands of people have lost their loved ones without even being able to say goodbye. 2020 has been the year of the coronavirus. 2021 may be the year of vaccines. We can wait several years while we continue to test vaccines and analyze their effect in the very long term deadline. You decide.